How much HP can I put on my out drive?

Jaysad

Seaman
Joined
Nov 5, 2008
Messages
67
I have a 1990 OMC Cobra 5.0HO.
How HP is it rated for?
What would happen If I go over that rating?
Would more HP give me more speed or low end power?

Thanks:)
 

gcboat

Lieutenant Commander
Joined
May 29, 2007
Messages
1,822
Re: How much HP can I put on my out drive?

I was told that they would handle 300 h.p. Now that's just the Cobra V8 versions - the Kings would be a little stronger.
 

sethjon

Senior Chief Petty Officer
Joined
Jun 8, 2010
Messages
692
Re: How much HP can I put on my out drive?

Why do you want more HP? If its a better hole shot change the prop. If its more top end change the prop. Unless you are barely getting the engine to perform, the current HP should be enough.
 

180shabah

Rear Admiral
Joined
Mar 26, 2005
Messages
4,995
Re: How much HP can I put on my out drive?

What would happen If I go over that rating?

Same thing that happens whenever anything is overpowered - wears out faster and or breaks sooner.

Would more HP give me more speed or low end power?

Maybe both, maybe neither.

In general you need at least 10hp to gain a single mph top end. This will have almost no effect on holeshot. Depending on howmuch power you gain, you may need to reprop to keep the revs down and that will have a negative impact on holeshot.


So, is this question just acedemic, or do you really have something you are trying to accomplish?
 

Jaysad

Seaman
Joined
Nov 5, 2008
Messages
67
Re: How much HP can I put on my out drive?

Thanks for your replys,
It sounds like reproping is the way to go if I want more low end power, and top end speed.
I have a 14 3/4 x 19, which way do I go for low end power, or top end speed?
 

picklenjim

Chief Petty Officer
Joined
Mar 11, 2009
Messages
528
Re: How much HP can I put on my out drive?

First thing you need to know is what is the max rpm the motor will turn right now. That motor should probably have a max of 46-4800 rpm. Lowering the pitch will give you a better holeshot and increase the rpm.Increasing the pitch will give you more top end and lower the rpms to a certain point where the engine no longer has the power to increase. So what you want to do is prop it to run in the recommended rpm range.
 

180shabah

Rear Admiral
Joined
Mar 26, 2005
Messages
4,995
Re: How much HP can I put on my out drive?

We need to know your EXACT WOT performance and EXACTLY which 19" prop you are running.
 

[OBC]Patch

Seaman Apprentice
Joined
Jul 6, 2010
Messages
45
Re: How much HP can I put on my out drive?

4500 rpm @ 41 mph, using a Solas stainless steel 14 3/4 x 19

One unit of pitch is worth 400 rpm.
A smaller number = higher rpm with less top speed and better hole shot.

One inch of prop diameter is also worth 400 rpm.

!!! If your prop is beat up, get it rehabbed and you will get rpm back. I lost 1500 rpm to a beat up prop.
 
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