View Full Version : Cooling system question: Prostar 190

08-02-2012, 02:56 PM
Question on the cooling system: Boat is a 2001 Prostar 190 with the LT1

Recently, boat had a problem where both exhaust side cooling hoses on the water pump were off the pump housing, after being to the mechanic for service. Upon picking up the boat from shop, we ran the boat and got about 2-300 yards outside the marina and blew a hole in the exhaust coupler. Shut down immediatly. Discovered both exhast hoses were off the pump. The owners explanation was that pressure had built up due to trapped old impeller particles (the impeller currently in the boat was new and fine) as well as system building up pressure as it wasn't drawing in water. Now, I understand one hose possibly having enough pressure (although I don't with the hose clamps tight...I'd rather expect a hole in the hose similar to the hole in the exhaust manifold coupler), however once one hose blows off, that would relieve the pressure, correct?

Also, is there a screen at the transmission cooler that can cause this blockage/ pressure buildup? This entire response from the shop seems a bit off line as we were told in the winter than they had to do some "emergency" block draining by an assistant and our theory is they never put the hoses/ tightened the clamps on the two exit tubes on the water pump. BTW, there was plenty of water in the hull of the boat when the coupler melted...but that was discovered after the coupler melted. There was no detonation due to overheating the block and no blown gaskets on the engine (meaning the engine was still cool). It seemed that water was making it through the engine, but not to cool the exhaust charge.

In short, my questions are as follows:

1. Is there a screen/ filter near the transmission cooler in the cooling system and can this cause a catastrophic failure if blocked?

2. Will impeller particles travel downstream to the transmission cooler when they break off or will they travel out the exhaust manifold exhausts?

3. Can pressure build up enough to "blow" the hoses off the exit couplers on the water pump? What would cause such a pressure buildup if so?

4. Why would the temp gauge not register an overheating condition under this scenario (I think I know the answer to this one)

5. If the engine is cooled correctly, how can water not make it to the exhaust system/ cool the exhaust charge?

We were charged labor and parts for the whole bill and won't go back considering how the problem was addressed. I really was looking for an answer for my own edification.

08-02-2012, 05:03 PM
1. Yes
2. The trans cooler is UPSTREAM of the raw water pump and I suppose it's possible but I've lost a few impeller fins and they....nevermind, don't think it's possible becasue the water goes thru the cooler/screen before the r/w pump on the Prostars.
3. Doubt it. SOme knucklehead just left them loose or disconnected.
4. No water to the temp sender = no reading on the guage. Hot air trapped in the block does not conduct enough to make the temp guage register.
5. If the water is flowing to and thru the raw water pump, there's pretty much no way it won't cool the exhaust. Hoses to the exhaust could get blocked with impeller parts, but not too likely as they're bigger hoses, 5/8 or 3/4.

By blown coupler I assume you mean one of the rubber parts on the exhaust. SInce you only went a little ways, my bet is that the engine was not getting sufficient cooling either, but had not run long enough to seriously overheat, whereas you'll burn up an exhaust hose in a couple minutes with no water running thru it.
How long have you had the boat? Have you blown any impellers in it and how long ago? If you know it's been a while since an impeller grenaded in the engine and it's run fine, then they are FOS (full of sh...) on the impeller chunks theory.

By the way, your 01 has a LTR engine I believe if it's the upgraded 350. I think the LTR's went back to cast iron heads and no reverse flow cooling vs the LT-1. That's good news in an overheat situation as the Lt-1 with aluminum heads were more susceptable to overhat damage, warped heads quicker being aluminum.

08-02-2012, 06:01 PM
Great reply, thanks Thrall.

Yes, by "copuler" I mean the rubber hosing after the manifold. We've had the boat since 2003 and change the impellers pretty regularly, lest the dry out and come apart...which we have not had happen yet. When the boat went it, it had ran all summer (2011) and was fine. We felt the impeller line was garbage, however when they said it would build up steam in the system and blow the hoses off the water pump, despite the hoses being clamped, I called B.S. My thought was the hose would blow a hole at one of the elbows well before it blew the hose (Both hoses!) off.

08-03-2012, 09:56 AM
I disagree with the answer to number 1. There is a screen at the transmission cooler, but this is on the suction side of the raw water pump, so it would not cause high pressures if it was blocked, but it would cause a high temperature engine condition.

08-04-2012, 05:56 AM
I disagree with the answer to number 1. There is a screen at the transmission cooler, but this is on the suction side of the raw water pump, so it would not cause high pressures if it was blocked, but it would cause a high temperature engine condition.

Just checked my 2000 Prostar with LTR if this is what you have? Transmission cooler and screen is on the downstream (pressure side) of the raw water pump, but the whole story sounds like BS to me. Two hoses blowing off together? Sounds like someone didn't tighten up to me.