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trim and handling Q? on 251 convincor

H

hharris

Member
ive got a 89 251 convincor, 330 hp bravo1 w/nosecone spinning a 23 mirage prop, my problem is when in the really rough water
i have to trim the drive all the way down and also run the tabs down to keep the boat level and make it plow thrue the large waves, which is normal but i dont like trimming down that far, its not all the way but really close to it, i can feel a little roughness in the drive when trimmed that low, so when i raise the drive up some to where im comfortable running it , it wants to slip or cavitate? ill be running it at the lake this weekend and will get some more seat time and hopefully figure it out!

where to trim
 
ive got a 89 251 convincor, 330 hp bravo1 w/nosecone spinning a 23 mirage prop, my problem is when in the really rough water
i have to trim the drive all the way down and also run the tabs down to keep the boat level and make it plow thrue the large waves, which is normal but i dont like trimming down that far, its not all the way but really close to it, i can feel a little roughness in the drive when trimmed that low, so when i raise the drive up some to where im comfortable running it , it wants to slip or cavitate? ill be running it at the lake this weekend and will get some more seat time and hopefully figure it out!

where to trim
 
oh and another reason i dont like to trim down that far is that it gives you that ( bow steer ) feeling which can be dangerous!

thanks for any convincor info!
Heath
 
I actually find myself doing the opposite in rough water... I trim it up a little higher and try to ride "over" the waves at a higher speed. But, it also depends on the wave size and their direction.

I would suggest playing around a little to find out what's comfortable to you. But I know I never go too far on the bow-down either.

FYI, I'm running an 84 convincor with a 454/TRS.
 
just was informed that it is probably the nosecone thats on this boat that is effecting its handling,

Ill be at LOTO this weekend so im going to try the trim up more and tabs down more and see how it does, i know if i trim up without the tabs the boat will take off like a space shuttle off of the top of each wave
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so hopefully i can get to a comfortable setting and figure it out, also i think i may be in search of a 4 blade 26 bravo prop, ANYONE know of one for sale cheap?
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thanks
Heath
 
tabs are used to stablize the boat .. not to bring it up on plane.. and yes you want to skip across the rough water.. not plow thru it.. if you keep riding "wet" as its called... you will "stuff" the boat.. which means you'll be swimming home. take your time and learn the boat.. then go see what she can do..
 
I also have a 25 convincor. I'm new to this boat. Does yours purpose easly? I like to trim up and ride over the waves also. But it seems this boat gets into a up and down pattern very easly. If I run it at 3,800-4,00 rpm it seems to stop. Or If I'm at a lower rpm and it starts I feed it more gas and it seems to break the mommenum. Is this a common deal with this haul or is there a better way to drive this boat? Thanks and sorry for the bad spelling.

Russ
 
Ruus G.,

A basic answer: Yes.

I've had my 25 for about 10 years now, and I put hundreds of hours on it. It is horrible at trying to keep it flat and on plane without the porpoising! HORRIBLE.

Since I re-powered last fall, my condition seems worse (don't know why, maybe it's in my mind)

I NEED to use the big tabs to get the boat on plane and too keep it from porpoising. Sorry Happy, but the tabs are needed on this hull for some reason. It is like a rocket when you launch, bow shoots straight up.

Mine is okay over 4000 RPMs also, but that depends on the load. If I have a few people and lots off fuel, I'm tweaking the tabs again.

I just ordered a new prop which I HOPE will take care of the mid-range problem.

It's not an engine trim problem, I've trimmed it in so far that the U-joints start to rumble the boat. There is no "happy position' for the outdrive trim without using the tabs.

TABS, use them and love them on this model.
 
I have an 89 251 also. I do not have any problems with trim and handling. The boat rides straight and true. I am running a 4 blade hydromotive prop, nose cone and a stern jack. The previous owner said the stern jack was the best thing he ever did to the boat. He said it really improved the handling.
 
has anyone tried drive spacers??? these let you drop the drive down from 1/2 inch to two inches.. this may help stabilize drivability..
 
Fastskipper,

What type of drive are you running with that jack?? That could be the final solution.

But you seem to have a lot of updates, which all seem to be installed to get rid of the porpoise issue.

I am using a TRS, and it runs deep! So, I doubt lowering a drive would fix the problem.

I am hoping this new 4 Blade I bought helps a lot.
 
hharris,

careful on that prop selection. I've just spent over a week of phone calls, reading, asking, etc to get a prop for my boat.

I was told, over and over again, that I couldn't turn a Bravo One 22" pitch.... let alone a 26!

I just ordered a Revolution 4, 21 pitch (which I am waiting to arrive if Mr. FedEx ever gets here) From all the "pros" I talked to, that seemed to be the best 4 blade for me.
 
thanks, the smac, im still contemplating on making any changes, the boat runs out awesome in smooth water, no tabs and let it rock, but last week at LOTO in the big water i figured out that the best ride i can get is at 3200 rpms cruising with the drive up a little from zero and the tabs down 1/2 way,
 
also being that this boat will be for sale this summer i shouldnt worry about throwing props at it just yet!

it does fine for what it is, a light narrow beamed 25 ft boat
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My prop just arrived at the office and I'll throw it on tonight to see how the boat reacts. I'll let you know if it fixes anything. If not, I'm going to be very upset at the Poker Run tomorrow.

I'm assuming LOTO is Lake of the Ozarks? I primarily run on Lake Erie, it gets messy out there and I'm looking for anything to help ride that chop.
 
yep Lake of the ozarks, its can get pretty hairy there too, especially in the mainchannel due to the damn place is surrounded by walls, you can very seldom read all the wave directions correctly,

do let me know if the prop changes anything
Heath
 
hharis,

I wanted to post my news with that new prop.

I lost 2 mph but got a much better cruising speed, better hole shot and a better over-all ride out of the boat.

It still has the porpoise problem (but only after I filled up the fuel with 31 more gallons)

Over all, I am debating on a 19" pitch, but I really don't know what that will do for me compared to the 21".

I guess you can say I am happy for now. But I would like a 19" and I would like to try a Mirage Plus too.
 
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