JAYSAD

Hello,
I have a 1990 21' Chris Craft boat with a ford 5.0 HO OMC Cobra engine.
I'm going to pull the engine this winter and rebuild it, and I'm looking for help on getting more HP from my 302.
The engine has not chage sence 1972, no emission, bone stock!
The boating guys said, just leave it alone, if it ant broke don't fix it, and WHY!
So, thats why I'm here!
What would you do?

08Steeda

I have the same engine in my Chaparral. Mechanic said the same thing to me! LOL

But I guess 55 mph on the water is fast enough for him!

JAYSAD

HAHA,
Dang man, thats a great looking ride!
I've been told to replace it with a 351w, and I would gain 60-65hp.

mjr46

heads cam and intake, and what do you mean the 302 hasn't changed since 1972?? 68 the 302 started and was 28 oz vs 50 up until 82 ish iirc, so someone has some misinfo in the 72 statement??

86 5.0L

plus didnt the 5.0HO start in '82? and cobra specific engines didnt pop up until 93(?)

08Steeda

Mine is a 98.

08Steeda

Only problem with the 351 is the weight disploacement on the hull. You might be a little small to get the right lift without to much cavitation.

from my research you could do a cam and a better manifold and go with better carbs, maybe even twin carbs. I also experimented with several 3 and 4 blade props and have a stainless from Mercury Racing and got at additional 5 - 7 MPH (Speed over ground) but you give up thrust by doing that. So out of a hole or from a dead stop it takes more to get the hull on plane. Which if your pulling skiers is NOT what you want.

I have a Typhoon Stainless that is the best all around prop for our use and it is kind of middle ground. Good for skiers and crusing. With 4 people I can get between 50 and 55 depending on wind and water conditions.

The other thing is if you put trim tabs on it, it will allow you to adjust the on-plane hull position. That along with raising as much of the stern drive out of the water as you can while under way without cavitation or causing a rooster tail you will go faster.

With everything out of the boat and just me on a windless day on the Detroit River I had a friend who is a local Police officer use his radar gun and had me at 62mph. Which on the water is pretty fast if you ask me.

Seems much faster for some reason than a motorcycle or car on land.

There are no emiision controls and such so they are pretty basic.

Also keeping the hull clean and polished will add MPH. Well not really add speed but it will not slow you down. Friction on the water is your enemy.

If I want to go real fast, a friend has a California Special that is 27ft but has a 1000 HP 454 with a SC on it. Damn thing was clocked at 117 mph. Too friggin fast on the water for me!!! But then he goes thru like 2 gallons of racing fuel every 60 seconds at WOT.