View Full Version : 89 prostar overheats the faster you go...why?

09-11-2007, 03:29 AM
Hi guys...I bought my first Mastercraft(1989 Prostar 190 w/powerslot) about a month ago and I had taken it out about 7 times and ran PERFECT!!! I took it up to Clearlake last weekend and chewed up the impeller bad. It was smoking something horrible. And heated up to about 250 and melted my Flame arrestor cover. I took it to get fixed and they said they did. They did a compression test, tested the electrical and spark. Everything was great. The only thing that was wrong was the the condensor was bad. They replaced it along with a new impeller. I took it out the same day I got it back and it fired up great. I got about 5 minutes out and it died. It wasn't getting any fuel. I thought the pump was bad or the filter was plugged. Turns out that the pump has a vent screw that was open. Took it in AGAIN and they said they fixed it AGAIN. Took it out the next day and it ran GOOD. It stays at 160 at idle BUT when i get going to about 25-30 MPH it runs up to about 190-210 degrees Farenheit. When I took it past 35 MPH the alarm was sounding. I brought it back down to idle and the temp quickly dropped back down to 160 degrees. If anyone out there knows what's going on or has any idea please respond to this thread. I don't want to give anymore money to those people. I would rather fix it myself. Thanks alot guys!

09-11-2007, 06:33 AM
Apparently you have impeller pieces blocking some of the water passages. The engine needs to be back flushed along with the exhaust manifolds. Everything needs to be checked for debris.

mark g
09-11-2007, 03:44 PM
i just had a similar problem but my impellor is ok, i was in a very hot country though, waiting to see if the same happens now i'm back home.
is there a thermostat in the engine i know it sounds a daft question but its got me thinking and its a little bit late to be getting the spanners out.

mark g
09-11-2007, 03:46 PM
:woohoo: :woohoo: i just realised i made enthusiast

09-11-2007, 04:23 PM
A friend with a TriStar 220 suffered from the same problem you described and what had happened is that when the engine overheated it got hot enought and there was no water that it melted the inside of the mufflers to where it restricted the flow. At idle the temp was okay but as he sped up the temp was rise.

H20ski Dude
09-11-2007, 04:32 PM
how do you back flush?

09-11-2007, 04:51 PM

09-11-2007, 05:07 PM
how do you back flush?
Maybe misstated, but removing the thermostat cover/thermostat, manifold drain plugs, hoses and anything you can open up beyond the raw water pump and wash out any impeller debris that may be lodged.

Prostar Rich
09-11-2007, 05:40 PM
I have a 90' Prostar and was chasing an overheating issue this spring after it was recommended to me to use a 160 degree t-stat. After chasing down all of the possibilities I went back to a 140 degree t-stat and the problem was solved.

Prostar Rich

09-11-2007, 06:16 PM
Make shure to check trans cooler for gunk. The water could have been resticted here starving the pump causing impeller to give out.

09-11-2007, 06:23 PM
Make shure to check trans cooler for gunk. The water could have been resticted here starving the pump causing impeller to give out.

And if you toasted the impellor, likely contains parts of the old impellor if the shop did not clean them out.

SunCoast 83
09-11-2007, 07:06 PM
I have one in the shop with the same problem. I think it may be the Transmisson Cooler as well. I am having a Sherwood filter installed as well. I hear its better for the engine.

09-12-2007, 02:05 AM
Ok...I will flush it out tomorrow after work. I hope it works, I called my usual boat mechanic and he said the same thing. That it might be I have some impeller pieces lodged somewhere in the hosing or the elbows. I hope that's the problem. Where is the trans cooler on my engine? How do I flush it out?

09-12-2007, 02:40 AM
Make shure to check trans cooler for gunk..

And check the windows for filth, muck! :D