Question for twin outboard guys

[70 ragtop]

Recently purchased a fairly crusty 84 Convincor with a pair of Yamaha 220s. Have been picking away at it, and have most of the crustys cleaned up, bottom paint removed, hull is all shined up and sealed, and engines are running pretty good.

Took it out twice this weekend to shake it down, and have some questions for those who have already been down this path
Setup is twin Yami 220s, 1.73 lowers, BOTH turning RH with Ron Hill Signature 26 pitch semi cleavers. Engines were bolted directly to transom three holes up. Was having water pressure problems first time out, so lowered them one hole.
I do have a left hand lower, but ratio is 1.85. Plan to find a matching RH lower

My questions are:
What props are you guys using?
Turning them in, or out?
I have heard in adds stern lift, also heard in adds bow lift....which is it
Where would you guestimate your boat balances?
At what point are you able to bring your trim tabs up, or can you?

Mine porpoises pretty bad without tabs. Drive it using the tabs, and its fine....but always tweaking it. What seems odd is at full throttle, it still wants some tab. I made small corrections lifting tabs at full throttle, and you could feel the boat accelerating pretty hard as tabs came up, but the nose started getting light, nose came up and it goes back into a fairly violent porpoising. Need to keep some tab down all the time to keep it stable.

Almost seems like the CG is just too far back. Had kids all go up under the nose (roughly 350lbs) at about 40-45MPH and slowing lifted the tabs. Started porpoising again, but was much better. I bet I would need 400-500 lbs up there if I went that route
Have been searching thru threads, and see this is pretty common on the Convincor, but most of what I have read is IOs, and the porpoising clears on the high end.

The semi clever has a lot of rake, it looks like a chopper with a flat TE, like a cleaver. Even though these are called semi cleavers, thinking these are bow lifters, and just the wrong prop for this boat.

Wanted to add jackplates, but thinking moving engine aft would make the porpoising worse

Would love to hear from those who have been there, and done that!

Thanks for the help, will post some pix once I setup a photo account. Open to suggestions on that as well

 

[miller]

I always heard turn them in for bow lift (which mates usually like). Turn them out for stern lift (which might help out your porpoising issue). They also claim out is much friendlier in docking situations. Clever style props usually lift the stern & slip like nuts whereas round eared high cup & rake props carry the bow better with less slip...especially the 4 blended ones. I've never had a boat like yours, but if it were mine I'd turn them in throw on a set of Mazco's RE4's & set those puppies way back some. JMHO

 

[70 ragtop]

I always heard turn them in for bow lift (which mates usually like). Turn them out for stern lift (which might help out your porpoising issue). They also claim out is much friendlier in docking situations. Clever style props usually lift the stern & slip like nuts whereas round eared high cup & rake props carry the bow better with less slip...especially the 4 blended ones. I've never had a boat like yours, but if it were mine I'd turn them in throw on a set of Mazco's RE4's & set those puppies way back some. JMHO

Thanks Miller

I've never owned a boat that acted like this either. Owned a few fast boats in the past, but never one that acts like this one. I thought something was very wrong, until I started searching the threads

Looking at it, I initially thought the same thing about pushing them back. I actually wanted to put brackets on it, add a nice splash well cover, maybe with a pad on top, and figured it needed bow lifting props. After the two quick test hops, I'm thinking that may be the wrong approach

 

[corey331]

I'm sure one of the many east coast guys who are running twin O/B Convincors will chime in. But if I remember right, they are all running at least a jack plate for set back. Others are running floatation boxes that are setting the motors pretty far back. The guys with the boxes are running really light weight Merc 2.4's or 2.5's though.

 

[JUPITER PULSARE]

Originally ran my 2800 with twin 2.4L 200hp Mercs spinning out, 24" of setback at 18" centers, turning Mercury 26 Choppers worked by DAH and lower units had Bob's Nose cones. Before adding the cabin the boat ran 72mph. It had a mid range porpoise that could easily be dialed out by giving the boat some throttle, trim up the motors and then back down on the throttle and she would settle down nice and stable. Then I swapped lower units, changed the cable positions on the shifter/throttle and spun the motors in...boat felt like it rode higher in the stern, less bounce, same speeds. Put a full cabin in (headliner, carpet, facing couches, v-birth pads, small galley, storage cabinet) and speed dropped to 67/68 mph. Re-rigged the boat recently with twin Merc 2.5L 200's, CLE gearcases, 24" centers, 25" of setback (with full cabin). I have more porpoise at mid speeds due to the shorter length of the CLE gearcase vs the Bob's but I'm slightly higher on propshaft height. Speed has dropped to 66.55 mph due to spacing the motors to 24" centers (but I knew that would happen as I was planning to switch to 3.0L motors and would need the 24" centers anyway. At roughly 50 mph or more the boat is rock stable. I will be re-rigging again (for the 3rd time) with some 3.0L Mercs or maybe 250xs's and will report back!

 

[DropTop5.0]

I have one of those twin 251s and its taken me quite a while to dial it in and I'm still dialing thanks to my good friends Bruce and Sammie.

Currently I'm running 6" of setback with Merc 2.5 200s with 1.87 lowers and 26P Hoss 3 Blade Hyperdrives and 26P 3 Blade Hydromotives. I am turning my props out.

Last year I had severe porpoise and I was not enjoying the boat as much as I thought I would and here is where I was and what I changed.

• I had 25" motors and I was thinking I was too deep causing porpoise. I was able to buy some jack plate adapters and get to motors up but it didn't help.
• I found I had bad motor mounts. I had them replaced and cut the motors down to 20" while they were apart but it didn't help.
• I found that my transom was soft and I replaced it with Seacast (thanks Bruce!)
• I got rid of those crappy small bennet trim tabs and replaced them with real K-Planes. The combination of new transom and K-Planes has solved 90% of my problem.

I recommend finding an eight foot piece of aluminum stock and insure it is flat and move it up and down your hull. MetalsDepot.com can UPS you a section if you can't find it locally. Start at your outer chine and move towards the V and see if you have any "hook" or "rocker" in your hull. I have been kind of thinking of it like a flat spot on my tires. If my tires are not balanced and true, it gets a little scary going fast on my crotch rockets and I'm thinking its the same thing with my hull. Its okay if I'm going 30 but I bought a Checkmate to go fast.

 

[DropTop5.0]

This is how i upload pics:

 

[70 ragtop]

This is how i upload pics:



Thanks for the great info guys!

Lets try some before and after pictures

Before, first time off trailer
http://s1378.photobucket.com/user/Mikeandjeannette1/media/IMG_6892_zpsq3szlw4y.jpg.html?sort=3&o=12

Right side sanded out
http://s1378.photobucket.com/user/Mikeandjeannette1/media/IMG_6988_zpsesfl1r2o.jpg.html?sort=3&o=8

Bottom paint removed, still need to finish the bottom....but maybe I have some other work to do first
http://s1378.photobucket.com/user/Mikeandjeannette1/media/IMG_6987_zpsuihx0wnr.jpg.html?sort=3&o=9

Buffing it out
http://s1378.photobucket.com/user/Mikeandjeannette1/media/IMG_7007_zpskvpq62q0.jpg.html?sort=3&o=4
Business end
http://s1378.photobucket.com/user/Mikeandjeannette1/media/IMG_7021_zpswj6rc9hj.jpg.html?sort=3&o=2

 

[70 ragtop]

I have one of those twin 251s and its taken me quite a while to dial it in and I'm still dialing thanks to my good friends Bruce and Sammie.

Currently I'm running 6" of setback with Merc 2.5 200s with 1.87 lowers and 26P Hoss 3 Blade Hyperdrives and 26P 3 Blade Hydromotives. I am turning my props out.

Last year I had severe porpoise and I was not enjoying the boat as much as I thought I would and here is where I was and what I changed.

• I had 25" motors and I was thinking I was too deep causing porpoise. I was able to buy some jack plate adapters and get to motors up but it didn't help.
• I found I had bad motor mounts. I had them replaced and cut the motors down to 20" while they were apart but it didn't help.
• I found that my transom was soft and I replaced it with Seacast (thanks Bruce!)
• I got rid of those crappy small bennet trim tabs and replaced them with real K-Planes. The combination of new transom and K-Planes has solved 90% of my problem.

I recommend finding an eight foot piece of aluminum stock and insure it is flat and move it up and down your hull. MetalsDepot.com can UPS you a section if you can't find it locally. Start at your outer chine and move towards the V and see if you have any "hook" or "rocker" in your hull. I have been kind of thinking of it like a flat spot on my tires. If my tires are not balanced and true, it gets a little scary going fast on my crotch rockets and I'm thinking its the same thing with my hull. Its okay if I'm going 30 but I bought a Checkmate to go fast.

I hear you on not enjoying boat like I thought I would! I did use a 4' level on bottom when I was sanding bottom paint off, but I can check it with something longer.

When you say hook, or rocker, I assume we are talking dips and bumps, or strakes/pad sides that have bulges or low spots??

I still have the small tabs, can see how longer tabs would be beneficial.

I think I found a lower to match my left tonight, hopefully it will have right ratio, and will be in good shape.


Not sure whats up with pictures, but link will get you to photbucket. I uploaded a few pictures from the past couple weeks of sanding and buffing. How do you get picture to show in the thread?

Thanks everyone for the input!

 

[Nick616]

How do you get picture to show in the thread?

Thanks everyone for the input!

If you copy the IMG tag from photo bucket ( just click on the link box ) and paste it directly in your reply the images should show up.

First Pic is below:

 

[70 ragtop]

If you copy the IMG tag from photo bucket ( just click on the link box ) and paste it directly in your reply the images should show up.

Thanks Nick

Lets try this again










It looks a little naked with no strips or decals, still need to buff deck, and cockpit, but want to get it running right, and make sure engines are good first. At this point, planning to go thru engines over the winter, pull floors and fix whatever needs attention. Transom was done by a previous owner, and their finish work in the splashwell was awful. Plan to fix that as well

 

[DropTop5.0]

You've done a lot of work bringing that beauty back. She looks good.

 

[70 ragtop]

You've done a lot of work bringing that beauty back. She looks good.

Thanks, Droptop
Debating going 100% resto back to original, or maybe make some changes.
The gray and light blue stripe inlaid in the gel are pretty thin, so I need to at least do some paint work on the gray areas. My old Exiter had the same blue hull, except the Exciter had silver metalflake in the light blue/gray area. Maybe do the gray in metal flake, like the exciter, or just give it an updated look, and respray the whole thing and add graphics...not sure. I have a soft spot for the 80's Checkmate look, and for a nice metal flake scheme, although I've never seen a Enforcer/Convicor with metalflake

Boat actually has a little bit of history. Was Inland Marines, in RI, 1st Convincor. They were one of the kickoff Yamaha dealers in 84, so they put the biggest Yamaha's available on it, and used it as their demo boat for 2 years. Took it to Boston, and RI boat shows a couple times. All the guys there remember the boat, and can rattle off all sorts of facts and figures, as well as everyone who has owned it.

While I don't exactly remember the boat, when I saw it for sale, it seemed familiar. I grow up in RI, about 10 min from Inland Marine, and bought my 1st boat from them in '85/86, so I must have at least checked it out back then

Hopefully found why the starboard engine was making wasn't making as much power as the port. The TPS on both engines were way off. TPS on these old Yamis is one of two primary sensors that controls timing. Got them dead nuts matched at idle, and WOT, synced them, and adjusted rigging and to keep them as close as I could thru the full range. Hope to get out this weekend to see if that did it for the engines

The lower unit I though I had found was the wrong ratio, so still looking for a 1.85/1 RH lower.

 

[knarloid]

Boat is coming together nicely 70 Ragtop!

I need to get the bottom paint off mine also.

I'm still getting used to mine, and always have the family with me, so not comfortable pushing it hard yet until I can run on my own.

Had it at 57GPS with them on Saturday on the Potomac with Droptop and Ramifications. Boat felt awesome up there. Hard to beat the hum of those 3.0L twins back there doing their thing!

I'm finding I need my tabs a LOT. While I don't fully bury them for takeoff, I do have them slightly dipped and only bring them up a click at a time until I feel the porpoising kick in. So drop them down 1 click, and then play with engine trim to get it higher. I think I threw a rooster at one point (it's the little things.....).

My motors are 25" mids, and are set back 6". I need to replace my transom at the end of the season and will add about 3" of height to the transom so I can mount the motors a little higher. They're currently at the top of the setback brackets.

I have a set of 26" Choppers since I bought it, but recently put a set of worked Lasers (24" I think) that Demag gave me and I found it really helped the ride.
I haven't played around with other props or gone for WOT due to time this summer and concern with the transom.
But we're all enjoying it so far since getting it back on the water!!

 

[knarloid]

Will you consider running the CT River Run later this season?
That's where I met the owner of my Convincor. He was running a Progression that day, and we were chatting about Checkmates. In previous years he had run the twin Convincor.

I told him I'd try to make it in 2016 with my boat.

 

[knarloid]

What did you use to remove the bottom paint?

 

[70 ragtop]

Boat is coming together nicely 70 Ragtop!

I need to get the bottom paint off mine also.

I'm still getting used to mine, and always have the family with me, so not comfortable pushing it hard yet until I can run on my own.

Had it at 57GPS with them on Saturday on the Potomac with Droptop and Ramifications. Boat felt awesome up there. Hard to beat the hum of those 3.0L twins back there doing their thing!

I'm finding I need my tabs a LOT. While I don't fully bury them for takeoff, I do have them slightly dipped and only bring them up a click at a time until I feel the porpoising kick in. So drop them down 1 click, and then play with engine trim to get it higher. I think I threw a rooster at one point (it's the little things.....).

My motors are 25" mids, and are set back 6". I need to replace my transom at the end of the season and will add about 3" of height to the transom so I can mount the motors a little higher. They're currently at the top of the setback brackets.

I have a set of 26" Choppers since I bought it, but recently put a set of worked Lasers (24" I think) that Demag gave me and I found it really helped the ride.
I haven't played around with other props or gone for WOT due to time this summer and concern with the transom.
But we're all enjoying it so far since getting it back on the water!!

Thanks Knarloid, good info

No kidding about the Lasers, I just sold one had sitting around for years.....figures

I used Citra strip from home depot on the bottom paint, then pressure washed it. Try not to get it on the gel, just the bottom paint. Took almost all the bottom paint off, and just needed a light sanding. I used 800 on a DA to sand it. Need to get back under there sand at 1500, buff and seal.... but I think that can wait until it cools off

I found another lower this weekend, two actually, so it now has counter rotating props. Per Jupiter Pulsares post, turning them in to start as it seems to really need some stern lift

What tabs are you running?
I've got 12x12 Bennetts, and they do smooth the ride out, but you can feel them dragging. Longer ones like Droptop have would likely be the ticket, but the constant tweaking really isn't that much fun if you're just cruising around
Been seeing a lot of negative comments on smart tabs, but I've got to say, seriously thinking of slapping a set on a trying them out. Only thing I'm worried about is once its sorted out, and I do start running it in the waves, are those tabs going to last, or break right off. They don't look very heavy duty

The CT river sounds cool, will try to make it
There is also a Banana Boat event in Narragansett Bat RI that sounds like a blast. Starts in Oakland Beach, goes out around Jamestown, back into to Newport. Stop in Newport, then head to Battleship cove in Fall River for lunch, and head back. Open to all boats, seems the focus is older classics...like what we all seem to own
For those who have never visited RI, there is some really great boating, and this sounds like a fun event. Was supposed to be in July, but got rained out, so I think its in Sept now. Info on Offshore only in Banana boat section. CONVINCOR told me about it, and hope he gets his V8 OB Convincor sorted out and he makes it as well.

Would be pretty cool if we had a few OB Convincors there.

 

[knarloid]

Thanks Knarloid, good info

No kidding about the Lasers, I just sold one had sitting around for years.....figures

I used Citra strip from home depot on the bottom paint, then pressure washed it. Try not to get it on the gel, just the bottom paint. Took almost all the bottom paint off, and just needed a light sanding. I used 800 on a DA to sand it. Need to get back under there sand at 1500, buff and seal.... but I think that can wait until it cools off

I found another lower this weekend, two actually, so it now has counter rotating props. Per Jupiter Pulsares post, turning them in to start as it seems to really need some stern lift

What tabs are you running?
I've got 12x12 Bennetts, and they do smooth the ride out, but you can feel them dragging. Longer ones like Droptop have would likely be the ticket, but the constant tweaking really isn't that much fun if you're just cruising around
Been seeing a lot of negative comments on smart tabs, but I've got to say, seriously thinking of slapping a set on a trying them out. Only thing I'm worried about is once its sorted out, and I do start running it in the waves, are those tabs going to last, or break right off. They don't look very heavy duty

The CT river sounds cool, will try to make it
There is also a Banana Boat event in Narragansett Bat RI that sounds like a blast. Starts in Oakland Beach, goes out around Jamestown, back into to Newport. Stop in Newport, then head to Battleship cove in Fall River for lunch, and head back. Open to all boats, seems the focus is older classics...like what we all seem to own
For those who have never visited RI, there is some really great boating, and this sounds like a fun event. Was supposed to be in July, but got rained out, so I think its in Sept now. Info on Offshore only in Banana boat section. CONVINCOR told me about it, and hope he gets his V8 OB Convincor sorted out and he makes it as well.

Would be pretty cool if we had a few OB Convincors there.

I've got the same K Planes as Droptop. They're awesome, but they do require quite a bit of tweaking, but I think that's just how this hull runs.

I've found it sensitive to cross winds, where people are in the boat while running and hitting wake or waves side on.
I've heard it said a lot that these are a real drivers boat for all that you need to monitor, but I'm loving mine so far.
A few more hours behind the wheel and I might get back to carrying a camera in one hand for the running shots of those around me!

I was chatting with Droptop at the weekend after we ran the Potomac with Ramifications, and we agree these hulls really want to cruise in the 50's. Anything much below the mid 40's is going to require a lot to manage the porpoising.
I also forgot to say earlier that I have 2 bags of sand (bags of Play sand from Lowes/Home Depot) up in the bow behind the mirror.
I took so much wet foam from under the vberth, that I knew I needed more weight up there. It does help, and I may add a third bag at some point.

I'll take a look at the Banana Boat event in RI. Never afraid to tow to a good boating location! (Lake George next week!)

 

[DropTop5.0]

Over the weekend we had quite a bit of wind and storm action and I found I did need to play with K planes a bit. I have quite a bit of seat time this year and I'm finding myself reacting faster and faster and not having to think about it so much.

I can easily go 30 to 40 mph but something changes a bit around 50 and the boat feels much more free and pleasant to drive. I do not have any ballast in the front of mine and I always start out with a full tank of fuel (70 gallons).

Kris - I need to borrow your Choppers next time we meet up.

 

[Ramifications]

I have the same hull as Jup - 2800SX. Same as the 251, but stretched 3'. This is my first real season with the boat. I ran it one time December last year with twin 2.4 200's and 28" of setback with them spinning in with 26p Choppers. The porpoise was almost unmanageable... I had to put the K planes down about 75% to make it manageable under 50 mph. The engines were set at 19" centers and I had basically no ability to use forward and reverse to maneuver the boat around the dock.

I repowered this season with twin Verado 300's and it is a totally different boat. Depending on the load in the boat, I don't need the tabs. When I have a few hundred extra pounds in the back, I need the tabs to manage to porpoise, but it only requires a little tab. My current setup is 6" setback, 27" centers (as close as I can mount them without touching), spinning out, 2.5" below the bottom and still playing with props and height.

I also put 200 lbs of sand in the bow since I do not have a finished cabin yet. I have run choppers and they work and have produced the highest speed so far (78 mph) but lower speeds and handling isn't that good. I have tried four blade hydromotives, bravo 1's and four blade BBlade Blasters. I had the best overall performance with the Bravo 1's. I will be installing a set of Bravo 1's and raising the engines another inch in the next week or so.

This hull is definitely a drivers boat. With the narrow beam and deep V bottom, they are sensitive to tabs and weight distribution. Try to even the load from port to starboard and and make minor adjustments to the tabs and let the boat react for a couple seconds before any other adjustments. It will take some getting use to, but you will find the comfort zone!

I would also like to attend the CT River Run this year! Droptop - you can borrow my 26p Choppers anytime.