496 HO overheating
 

Looking for some help. I have a 2001 275z ST with a 496 HO and Procharger. It overheats after running on the lake for about 15 minutes and the alarm goes off. If I let it idle for about 10 minutes it cools off and its good for another 15 minutes. I have a new impeller and thermostat. Plenty of antifreeze in the closed system. But when I got it home and put muffs on it it would not overheat. Any ideas?

Re: 496 HO overheating
 

trathbun2,

What does your temperature gauge read? It could be wiring. the engines water pump, a restriction, etc.

I assume that you are running it with the muffs on at idle speed.

Shabah 198SE

Re: 496 HO overheating
 

The Temp was @ 210 degrees I lasered it to verify and it was accurate. I am replacing the impeller that the deale said it replaced when I winterized and the thermostat. I am checking for restriction because I replaced the water pump last August. I took the prop off and ran it at higher RPM's to try to get the temp up. It stayed at 170 degrees. I am checking the exhuast manifold and riser for some sort of restriction. Keep the ideas coming!. The dealer got an earfull and I won't go back. The wiring is a good thought since they blew every fuse and breaker when they reconnected the batteries and reversed polarity. Thanks!

Re: 496 HO overheating
 

I think you are on the right track with restriction of flow. Since it only overheats under the load of being under way.

You may need to take apart the expansion tank, I have heard of debris getting caught inside there and restricting flow. That would account for only overheating under the load when under power and not in the driveway on the hose.

Wne you take it apart, you need to be mindful of the proper way to disassemble the tank, and reassembly, what type of closed system is it? A San Juan, or something else? And I agree with pulling risers off and checking for obstructions and it is not that difficult to do.

Re: 496 HO overheating
 

trathbun2,

Seeing that it lazered at 210 degrees, I doubt that it is a wiring issue. If this is a new issue, a stuck or partially stuck thermostat is also a possibility. Why did you have the thermostat and the impeller changed?

Shabah 198SE

Re: 496 HO overheating
 

I change them every year. But, I took it to a shop this year because the boat was broke into and they were repairing it. But, I now have the impeller out and it was never changed and the rubber is cracked. I pretty sure the thermostat wasn't changed either. I will keep you all posted as I check everything out. Thanks for the help.

Re: 496 HO overheating
 

So the dealer didnt change them but charged you for it? Stuff like that makes me want to go postal.

Re: 496 HO overheating
 

How is your water pump? When that happened to me, it turned out that the water pump was not circulating the water around the closed system. Even after I changed my impeller, it turned out that my water pump was out too.

Re: 496 HO overheating
 

the muffs provide water that is pressurized to some extent to the engine bay, your outdrive laying the lake does not. Id be looking at the impeller again in the outdrive

Re: 496 HO overheating
 

It took a while but, we found the overheating issue. The Pro Charger was leaking due to it not being winterized by the dealer. So there was water being pumped right into the cylinders instead of air. In turn water got into the crankcase oil and turned to foam at High RPM's. So, I am now looking at removing the heads, replacing the valves, replacing the rods an new rings for the pistons and removing the procharger. Total $8,800 in repairs. I am seaking legal action since I paid to have it winterized and have it in writing that I requested the Pro Charger be drained and blown out as well. I know the rules so, I would mention the dealers name. But, if you are in Oklahoma and need assistance in finding a reputable dealer. Get in touch with me. It could have been worse. It could have been $17,000 for a rebuilt motor. Thanks for all the advise. The best advise is get 2 opinions and make sure that if they don't winterize you boat immediatly it needs to be inside a heated area. not out in 28 degree temperature. Thanks to all! Ted