Poor Holeshot & Overheating

Randy, 

I have a 77 Varmint that has had the pad reworked for racing.  Im running a 91' OMC Looper (200) thats pushing somewhere between 250 to 280 hp.  It's set about an inch below the pad with eight inches of setback.

My problem is this;  when I nail it coming off the line it just sets down and blows out.  I have to get it moving to about on plane then nail it for it to take off right.  Currently running a 28 big ear (merc) that's been butterfly cut and repitched to 30.  How can I fix this problem.  I have tried raising and lowering the motor but to no avail. 

Also having an overheating problem.  I've put two new pumps on the motor, had it torn down and inspected, but still the problem arises when running around 50 or so cruising down the river.  I'm lost on this one!!!!  (the foot has a Bob's nose cone and lower water intakes installed at his shop)

Any helpful ideas or suggestions would greatly be appreciated. 

Thanks
Fred L.

 

Fred, 

Thought a lot about your Varmint. Most looper OMC's would make 250 crank horsepower right out of the box. I don't know the details of yours but it shouldn't make any difference in our discussion. Almost every OMC I've run ventilates excessively on take off with a overhub prop. I don't know why as it seems nobody else has that problem. We have always had to put more "roll" in the leading edge of the prop to get them to bite. The OMC gearcase must push more exhaust over the blades or something. Have a "good" prop shop put more acceleration into it. If they don't know what I'm talking about search elsewhere. A couple of years ago I had an OMC do the same thing with the water flow. We found a base gasket short-circuiting the exhaust and cooling passages. The exhaust bubbles would make the engine overheat. Check it out. Other possibilities are a high compression motor will lightly detonate in the midrange and cause the water around the heads to boil in the cooling  jacket. That would turn up as overheating. I'd go slow and hunt for the most remote things you can think of. It's got to turn up. 

Good luck
Randy

 

 

Please submit whatever questions you have to IHRTechTalk@yahoo.com.  All questions and answers selected will be displayed on this page as they come in.  Note: though all boaters are welcome, priority may be given to I.H.R. members.  Randy can not be held responsible for any advice given.  Though his information and expertise is second to none, he has no control over what you do with your boat.  It is up to you to boat safely and act responsibly, and his advice is only to be used as a guidance for your high performance boat/motor of which you are the one responsible for the risks involved.

Thanks,
Mark C.

 

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