View Full Version : '97 Prostar 190 LT1 - overheating

05-24-2008, 12:27 AM
ok... long story short... chewed up impellar end of last season... noticed it when temp spiked and boat idled itself down... replaced impellar and both thermostats 140 lower and 160 upper...

ran boat this evening first time in water since last season. boat ran good for about 5 min at idle to 2500 rpm... got it up to about 3750 rpm and ran for a few minutes... turned around headed back to cabin soon after the boat idled itself down... noticed my therm wasnt reading on the dash?? (what could be prob with this??) so docked and begin search... impellar is good and pumping sufficient water up... seems like water pump could be bad... no return water coming out of block back to pump to exhaust... where do i start? or what does this sound like to some of you with more knowledge? could it be my water pump??? took cover off of it and just turned key to see if i could get anything... it turns... plenty of water flow from raw water pump up to it but nothing coming back out and no temp reading on dash....

please help asap!!! makes me sick that its memorial day weekend and first time out for season and the d**n boat is out of commission...

thanks, ben

05-24-2008, 10:48 AM
plenty of water circulating... But still no temp reading and boat is self idling down like its hot! What could it be? Temp sending unit? Ecu need reset??? Please advise...

05-24-2008, 02:56 PM

I just did a quick search for "overheating LT-1" and came up with several threads. Might be worth looking through them for some place to start with your situation.
Hope this helps

05-24-2008, 04:17 PM
Ok got temp guage working... Bad sending unit replaced.. Now the confusing and frustrating issue... Boat runs hot when drive engaged but when placed in neutral it immediatly cools back down! I'm so confused and haven been on phone all day with Rambo marine and they are as well... Unsure of what else to try without taking boat into them... Any advice??? Ideas??? Hoses are clear and transmission filter is clear... No reason it should run that hot...

05-24-2008, 06:13 PM
what about the exhaust risers/manifolds......I'd check for blockage on the risers where they bolt to the manifolds.....and also where your hose attaches to the risers=should be clear, maybe they're plugged up and not allowing all the water to get out fast enough.

05-25-2008, 01:57 AM
Man, I hope I am wrong on this point. I would be concerned about combustion gasses entering the cooling system by your discription. I know from experience with autos and trucks a rapid increase in temp when under load would point to a blown head gasket at the least.

With boats we need to be concerned about the exhaust manifolds as well...

Tell us how did you winterize last time. Did you have consecutive days of hard freezes during this past winter?

05-25-2008, 10:49 AM
freezing shouldn't have been an issue... Stored in building and system completely flushed and filled with standard antifreeze. However did notice when changing oil a lil water in oil but very little.

05-26-2008, 01:08 PM
OK, I read through most of those posts after running a search for "overheating LT-1" and the recurring theme was centered around the thermostats. Make sure you have the correct ones and they are installed correctly. A few members made note of the need to purchase them from a dealer for the best performance. One member had a useful tip for flushing out the old impellor from the block. Others mentioned the need for flushing out the bypass hoses as they may become blocked. Hope you figure it out and let us know so we can learn from your experience.

05-26-2008, 01:22 PM
freezing shouldn't have been an issue... Stored in building and system completely flushed and filled with standard antifreeze. However did notice when changing oil a lil water in oil but very little.

Now that's not good!

05-26-2008, 02:39 PM
Ok I know water in oil isn't good... Points to head gasket but ive paid close attention and oil pressure is good and since oil change the level isn't fluctuating so I don't feel like I'm getting any water in oil now...