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PROPer setup

PapaMaC

PapaMaC

Member
I don't know much about props other than the wrong pitch can be a real b:devil:tch.

I finally got a chance to take my '89 Spectra 170 BR out by myself on 1/2 tank minimal gear in a dead flat canal with a little wind. After I found her sweet spot on the tilt I maxed out at 45mph gps @ 5600 rpm. I have an '89 Johnson 120hp v4 with the VRO disconnected and I premix 50:1. The current prop is a S.S. 3 blade, don't know the make or pitch. I do have an Attwood hydro-stabilizer ( http://www.iboats.com/Hydro_Stabilizer_F_Ob_S_Sterndrives_50_Hp_Up/dm/view_id.65914 ) mounted and haven't run without it, nor do I plan to.

Can someone throw a few links at me that can help me understand which prop would be best suited for me? I'm not expecting to get 60mph out of a 120hp but 50-55mph would be nice :surf:.
 
You may be able to get that boat over 50 with a prop change. 5 mph is a lot to ask of a prop, especially since your rpms are good. I just did the same thing with my Pulse 170, I put a Michigan Wheel 3-blade 21" prop on my 135 Merc and got 55.5 mph gps (two-way average).
Your RPMS were good, so look for big ear 3-blade props that'll provide bow-lift. Stay away from cleaver style props. Try as many as you can. I dont know the Johnson props very well, have you tried the Evinrude web site to see what props they offer now? Do you have any dealers near you that will let you try props?

I'm getting ready to install a planing-aid, so I'll find out if I hurt my speed any. Here's the one I decided to try:

36483_L2.jpg


I got it at a West Marine store while I was picking up a new ski tripod. I figured for $49, what the heck. I do need help in the 20 mph range keeping on plane. Hope I dont hate it when I'm WOT or making fast turns
 
I would guess that you're running a 19p or 20p prop. (Based on your L/U probably being 2:1) Check out this link, and you can see where you can go...

http://www.boatramp.com/prop_applet/PropAnalyzerAppletG.html

You could probably move up to a 21p or 22p and get to 50 or 52 mph respectively, but you're going to sacrifice your 'git up' and could drag your wot rpm down (which would keep you from getting to the speeds I mentioned)

Good luck- I'm gonna need some too, I'll be trying to wring out prop issues pretty soon too...
 
P.S.

When I put my numbers into the prop slip guide that jlehman posted above, I had much less than 5% slip. What that tells me is my 21" Michigan Wheel 3-blade is REALLY more pitch than what's stamped on the hub. Or, my tachometer is wrong at the top end.
 
There's always the possibility that the app is wrong, I definitely didn't make an attempt to verify the math! Assuming that the app is correct though, small differences in RPM greatly affect speed, and I doubt that many tachs are terribly accurate.
 
JW what about the other "no holes" in the cav plate ? post some numbers for us i'm curious how that works vs. tabs ?
 
Try a factory OMC/Bombardier "Viper" 3 blade stainless. They've got a nice "swept back" blade profile and long ears for good lift. And don't be afraid to prop it up a bit. That 120 was not built to be a "rev monster". It'll still run good down in the low 5000 range. In fact, 5200-5500 is about the sweet spot on those things. You will probably get the best top end from an old style "Raker", but the only thing those props do well is run fast in a straight line. They tend to slip BAD at mid-speeds with any positive trim, and generally will completely blow out in mid/slow speed turns.
I've run A L O T of props on alot of boats.....but I've still never had an aftermarket prop perform as well as an OE prop when it comes to "overall best performance". That's just my experience, for what it's worth!
 
zstevens said:
JW what about the other "no holes" in the cav plate ? post some numbers for us i'm curious how that works vs. tabs ?
Click to expand...


The $119 clamp-on wasn't in stock at the West Marine store, so I cheaped out and got the hole-driller kind :rof:

I'm hoping this SE200 is small enough to stay out of the 'way' when I'm running fast, but big enough to hold the bow down and keep the prop from blowing out when running slow and turning. That's another problem my 21' Pulsare didn't have that I forgot the 17' boats have. Both of my 17' Pulse boats: 1) Too much bow-rise on take-off. 2) Prop blows out easily. 3) Poor performance in the 18-24 mph range.
My Pulsare had none of those issues.
 
JW said:
Both of my 17' Pulse boats: 1) Too much bow-rise on take-off. 2) Prop blows out easily. 3) Poor performance in the 18-24 mph range.
My Pulsare had none of those issues.
Click to expand...

I have a LOT of bow rise on take-off but it completely planes out in less than 3 seconds, likely from the hydrofoil. I've been testing the motor for about 6 hours total so far without blowout, hopefully it stays that way. My only problem at low speeds is its hard to get the bow down, maybe I'm just still getting used to it.
 
Papa, you shouldn't be getting ANY bow rise (or very little) with thay hydrofoil on the engine. Are you sure your power trim is running all the way down?
 
Wide Open said:
Papa, you shouldn't be getting ANY bow rise (or very little) with thay hydrofoil on the engine. Are you sure your power trim is running all the way down?
Click to expand...

I only get it when I push it from idle to WOT. If I bring it up slowly I don't see any bow rise.
 
Looks like a raker or possibly a sst. How deep do you have the motor? The 120 looper is a strong engine I would think you should see 58-60. Rick
 
That's not an SST. The SST has a seperate diffuser ring. And it's definitely not a Raker because the Raker has a straight hub. In fact, looking into the hub in that picture, it's not a factory OMC prop. The to edge of the hub would be flat with a 6 digit part number if that was the case. It really looks like a Michigan Wheel prop to me, but an old one at that.
 
a spectra is a pretty heavy boat for 17' 1100 + lbs and that is brand new withing nothing in it. add in some water soaked flotation foam and engine/gas battery etc. and you are looking at 2000+ lbs. You may not be able to do much better than 45 with 120 hp. I had a 140 on my old mx15 (500 lb boat) and maxed out at 55 on gps. I also agree tat 5600 is a litte much for an old V-4 go up 1-2 pitch with a new more efficient prop and you will most likely kiss the 50 mhp mark. -shane
 
Wide Open said:
That's not an SST. The SST has a seperate diffuser ring. And it's definitely not a Raker because the Raker has a straight hub. In fact, looking into the hub in that picture, it's not a factory OMC prop. The to edge of the hub would be flat with a 6 digit part number if that was the case. It really looks like a Michigan Wheel prop to me, but an old one at that.
Click to expand...

it says kk144 on it... no other markings
 
JW said:
You may be able to get that boat over 50 with a prop change. 5 mph is a lot to ask of a prop, especially since your rpms are good. I just did the same thing with my Pulse 170, I put a Michigan Wheel 3-blade 21" prop on my 135 Merc and got 55.5 mph gps (two-way average).
Your RPMS were good, so look for big ear 3-blade props that'll provide bow-lift. Stay away from cleaver style props. Try as many as you can. I dont know the Johnson props very well, have you tried the Evinrude web site to see what props they offer now? Do you have any dealers near you that will let you try props?

I'm getting ready to install a planing-aid, so I'll find out if I hurt my speed any. Here's the one I decided to try:

36483_L2.jpg


I got it at a West Marine store while I was picking up a new ski tripod. I figured for $49, what the heck. I do need help in the 20 mph range keeping on plane. Hope I dont hate it when I'm WOT or making fast turns
Click to expand...


Hey, guess what? I was reading my Trailer Boats magazine this month and in the back is an ad for the SE200 and SE300 and the NEW SPORT CLIP that allows this thing to be mounted without drilling any holes. I wrote the company an e-mail and got a response. I called:

Norris Misemer
Sport Marine Technologies, Inc.
P.O. Box 1889
Pilot Point, TX 76258
940-686-9000
940-686-9900 fax
800-201-9095
sportmarin@aol.com
sesport.com

and ordered a Sport Clip from him, as I haven't mounted my SE200 yet. I don't think it's at any retail stores yet, so he's sending it to me factory direct for approx. $45 delivered. I'll probably do a before and after test and post it on this site, as I'm sure we're all interested in if I lost any top speed and how well the new clip works.
 
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