I have a 2002 Supra Launch with a 350 GM (Vortec) engine (marinized by Indmar)...it's an inboard running through a V-Drive. The boat is new to us...we've had it about 20 hours worth, and just back from a trouble-free week on Lake Chelan. There is a total of 190 hours on the motor, and the previous owner had it winter-ized/de-winterized by a shop, and kept it stored in a heated barn over the winter. The boat is in excellent condition. This is my third boat...the first had a closed I/O volvo system, the second a Mercruiser I/O freshwater system. Neither of the first two were trouble free...by any means, so I've got some idea of what I'm doing...my wife says just enough knowlege to be dangerous.
We keep the boat moored on a nearby lake. We are up in the lilly pad area, and the water isn't very deep, but we only draw two feet, so it hasn't been a problem. My son was out and noticed the temp getting up over 175, and then saw it spike up to 250-ish. The limiter kicked in and forced the engine into limp mode. He shut it down, opened the hatch, and let it cool. After it was cool, he idled it back to the dock...fortunately he wasn't far.
So here's what I've done to trouble shoot:
- I have access under the back seat to the transmission cooler and raw water inlet area. I removed the hose from the raw water inlet to the transmission cooler. I can blow into the hose, and I get bubbles under the boat. If I lower the hose to water line level, I get water rushing through the hose into the bilge. I re-attached the hose.
- I removed the second hose (outlet side) of the transmission cooler, and I can blow through the transmission cooler and get bubbles under the boat. Everything is re-attached.
- I checked the impeller. This is where I really expected there to be a problem. I removed the pump and pulled the impeller...everything looks great...the impeller looks new, no cracks. The pump cover had some discoloration on it and a little bit of scoring, so I used emory cloth on a flat surfact to clean it up. I didn't get all of the scoring off, but it cleaned up nicely. Replaced the gasket and put it all back together again. The hoses have a definite order in which goes where, so I'm confident they went back on properly.
- I pulled the thermostat. It was rusty looking, so I replaced it. The new thermostat opens properly at temp.
- I pulled each of the hoses from the temperature housing that go to the manifolds. When I blow into them, I get some resistance, but it blows back out the temperature housing that the hose came off of. No obstructions.
- I have a hot water shower that is plumbed into the top hose that comes from the impeller. I pulled this (small) hose off and ran the engine. At first, It dumps a stream of water into the bilge. Then it pulses water into the bilge, at a decreating rate...than it didn't dump any water at all, it just hissed and steamed. Temp was going up so I shut the engine down.
- I'm about 3 miles from the boat launch, and I don't relish the idea of limping the boat down to get it trailered...I will of course if I have to.
- I have noticed that there isn't a lot of water in the hoses that go in and out of the thermostat housing. I'm at the point where I keep re-doing and re-checking the things I have already checked.
Any suggestions would be greatly appreciated!