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Over Heating Problem 502's Scarab 33 AVS

Old 06-23-2007, 01:21 PM
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Default Over Heating Problem 502's Scarab 33 AVS

I have a problem and need some help.

I got a noise violation ticket with my 1999 Wellcraft Scarab 33’ AVS with twin 502 MPI’s. My engines are bone stock with no modifications. Against my better judgment I had installed a product inside the exhaust tubes that advertised a reduction of 10 dbi’s.

This is only where the problem begins.

It is my theory that inline mufflers or baffles caused the subsequent over heating problem. Although the marina says “No Way” I am ever more convinced that this is what started the initial over heating problem.

Since removing the baffles I have completed a leak down test, which although not perfect test good, replaced the exhaust manifolds, replaced impellor pump with complete assembly’s and replaced the thermostat.

The boat runs at idol for as long as you want without showing any signs of overheating, stays right about 150 degrees, consistent with no jumping of temp. When increasing the RPM’s the temp slowly increases about 2500 rpm’s rises to 180 degrees, pushing 3000 temp gets to a point where you need to shut the motor down at about 200 degrees. Let the set for a bit to cool, restart at idol temp goes back down to 150.

I am wondering if this is a possible head gasket, should I re-look at impellor pump, possible main engine water pump.

Any thoughts and ideas? Remember (my opinion only) this problem originally started because these baffles where installed creating the original overheating problem. At the same time is originally overheated the starter took a crap; I am not sure if it got hot and pushed a weak starter over the edge? Also when working on the impellers the marina noticed and replaced to “cracked” fuel injectors. So now, $2600 later, the boat still over heats.

Please help!!

Last edited by newkerofmi; 06-23-2007 at 01:38 PM.
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Old 06-23-2007, 03:39 PM
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I had an over heating problem once, and it was caused by my oil cooler being clogged......
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Old 06-23-2007, 10:31 PM
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make sure your sea pump belt is not slipping at high RPM, or a pulley that my be spining on a pump shaft.....What did the marina say is causing it?
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Old 06-23-2007, 10:57 PM
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Originally Posted by Tricky919 View Post
I had an over heating problem once, and it was caused by my oil cooler being clogged......
ditto - I had a problem that acted this same way and it was because I had sucked some sand/mud into the oil cooler. Only takes a few minutes to take it off and see if some of the channels are clogged.
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Old 06-23-2007, 11:00 PM
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if the boat has much salt water use check the hose connection between the gimble at the top to the rubber hose going to the motor it has 2 bolts attaching it to the top of the gimble take it off and check if the little plastic fitting has swollen........and check the front side of the oil cooler
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Old 06-24-2007, 09:49 AM
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Sounds like the engines have a few hours on them,,, if you have checked all the water flow areas and the pumps are feeding enough water to the engines it will problably be a bad head gasket or cracked heads that is causing your problem,,,, good luck with it !!!

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Old 09-06-2007, 01:02 AM
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I got the same boat with the same motors and had the same problem. when the impeller goes bad the pieces get in the bottom of the oil cooler. Pull the bottom hose on the cooler and gently poke around up in there with a tool and feel for the rubber parts.
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Old 09-06-2007, 11:23 AM
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Pull the muffler inserts and see if the problem gets better.
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