4.3L w Cobra outrive- which prop setup is best?

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ChrisCraft88

Recruit
Joined
Mar 29, 2013
Messages
5
I have an 88 Chris Craft, 205 limited with an OMC 4.3L, Cobra outdrive. Mod no. 985269 serial no. T0556255.

Currently I have a stainless, 3 blade Viper prop on it. The only numbers I can see on the prop are, 15x17 and 174889.

The issue I have, it is okay getting out of the hole, but top end, seems weak. I am currently getting just over 43 mph and I am sure the boat is capable of more.

If anyone can help me with some ideas.

Thanks
 
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steelespike

Supreme Mariner
Joined
Apr 26, 2002
Messages
19,069
Re: 4.3L w Cobra outrive- which prop setup is best?

We need your wot rpm.Do you know the gear ratio?
 
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Starcraft5834

Lieutenant Commander
Joined
Jun 2, 2013
Messages
1,677
Re: 4.3L w Cobra outrive- which prop setup is best?

Get a 4 blade prop, Solas 15p 14.75 dia.. your hole shot will not just be "ok", with 4 blade will be terrific, you will lose a few mph, hole shot improvement is worth it,, was for me
 
jestor68

jestor68

Commander
Joined
Jun 12, 2012
Messages
2,308
Re: 4.3L w Cobra outrive- which prop setup is best?

You prop a boat with an accurate tachometer, to get the WOT rpm within the recommended range(4400-4800 in this case).

As Steelspike asked; Whether or not it's capable of more depends upon what WOT rpm it's turning now with the 15 X 17 pitch prop.

Since the OP did not state what performance he's after(all around, acceleration, top speed, etc), we cannot start throwing prop sizes at him until we have an understanding of what the goal is.

We need more information. :)
 
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ChrisCraft88

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Mar 29, 2013
Messages
5
Re: 4.3L w Cobra outrive- which prop setup is best?

Thank you all. I will get back to you re the WOT.
My goal is to have a decent whole shot and get more top end. It seems once I get about 3/4 throttle, there's nothing left but RPMs. I will confirm speeds and WOT RPMs as soon as I can get back out. I am not sure about gear ratio (is there a location on the unit where I can find out by numbers?)
 
Levinz11

Levinz11

Senior Chief Petty Officer
Joined
Apr 1, 2012
Messages
726
Re: 4.3L w Cobra outrive- which prop setup is best?

My 88 OMC only pushes my boat to about 45 at 4600 RPM. My boat is 18.5'. 43 in a 20' boat doesn't sound too bad actually. I have a 4 blade Solas 14.5x19 aluminum.
 
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Starcraft5834

Lieutenant Commander
Joined
Jun 2, 2013
Messages
1,677
Re: 4.3L w Cobra outrive- which prop setup is best?

4 blade= increased thrust for best hole shot......top speed possible will not be achieved by a 4 blade.. I'd get a 4 blade, you can tow ski/tube and still be good top end speed. make sure your rpm/tach is within WOT range for your engine
 
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