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90 hp turbojet overheat

 
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ralph



Joined: 22 Aug 2007
Posts: 2

PostPosted: Wed Aug 22, 2007 9:15 am    Post subject: 90 hp turbojet overheat Reply with quote

Hi Guys!
I need help with this one! I replaced a 1995 90 hp OMC turbojet powerhead in a 14' BW Rage. The original overheated and seized. The replacement was from a rebuilder in Fla. The rebuilt is overheating too.
It runs fine on a garden hose hooked up to the inlet hose taken off at the transom plate. In the water, it overheats. With no pump to question, I am wondering if the impeller is worn and not providing enough pressure to push the water up through the block. All passages were cleaned in the engine mount plate before assembly. Got any ideas??? I have a lot of mechanical experience with marine engines, almost none with jet drives like this. Can I perform a pressure test similar to an outboard???
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MikeW
Senior Member


Joined: 01 May 2006
Posts: 680

PostPosted: Fri Aug 24, 2007 1:35 pm    Post subject: 90 hp turbojet overheat Reply with quote

Hello Ralph, have you replaced the Thermostat?
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ralph



Joined: 22 Aug 2007
Posts: 2

PostPosted: Mon Aug 27, 2007 7:37 am    Post subject: turbojet o/h Reply with quote

Yes,
there are two of them as well as the pressure relief valves
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boatScotty
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Joined: 07 Nov 2006
Posts: 229
Location: Pacific Northwest

PostPosted: Thu Sep 06, 2007 9:28 am    Post subject: 90 hp turbojet overheat Reply with quote

So, have you looked at the impeller? A worn or damaged impeller (or the housing it is in) would cause you to overheat. I have to agree, you have a cooling delivery problem.

Is there any obstruction to water coming in?
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Boat Scotty

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boatScotty
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Joined: 07 Nov 2006
Posts: 229
Location: Pacific Northwest

PostPosted: Thu Sep 06, 2007 11:13 am    Post subject: 90 hp turbojet overheat Reply with quote

OK, so I am having a harder look at this and let me get this straight...

It is a jet drive and the cooling comes from the drive impeller, right?
It runs cool when you put on a hose, but hot in real life, right?

You look to be left with something blocking the cooling system. I can often find these things with a digital infrared thermometer. Seeing if there are any really hot spots to the engine helps. Where the water comes out (pee hole or in the jet) check the temperature while doing the hose routine.

The engine will run hotter in the water than with a hose - pushing the boat is work!
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Boat Scotty

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