Trojan Boat Forum

OK .. new boat to us..... 74 Trojan 30' Sea Raider hardtop.....was having issues where the water temp would go off the scale (220+) when I tried to bring her up on plane...lots of steam in the exhaust..thought it was the impellers... went to change the impellers today and the ones that are in there are in great shape! I did find a piece of "old" impeller lodged in the pump - thought that maybe this could cause cavitation.. or impede flow... removed the old piece - all of the vanes on the existing impellers are solid and in great shape... while I was down in the hole - thought that I'd check the thermostat to see in any other pieces were to be found - none... I did find that the thermostat was pretty easy to open with my thumb??? not sure if this is normal... shouldn't it be somewhat stiff??? when I water tested the temps went to about 215 or so and lots of steam in the exhaust......but no sudden "blowing off the scale" issue that I had before....

Does this sound like thermostat issues?? what temp thermostat should I be running - the engine is a 400M Chrysler...

Thanks,
T Dave

first and foremost are your gauges accurate????? Borrow or buy an I.R. gun and check the temp at the thermostat/sensors and ensure you are in fact overheating. If you are and it is not just a wonky gauge and you have found old inpeller parts check your trans cooler for bits and backflush you engine, check back when you have done this

Dave

I believe it's 140 deg raw water cooled and 160 deg fresh water cooled. If there was one piece of impeller stuck in the pump from a previous failure, there may be more lodged in the system up stream. I would back flush from as far up stream as possible. Usually, a good first place to look as it's normally the first piece of hardware is the oil coolers. If pieces got by the pump, they may be stuck there. If fresh water cooled, they may also be in the heat exchanger.

check the oil and trans coolers fot other impeller parts . you may not have a oil cooler but you do have a trans cooler for sure .


make sure the hose going to the pump from the tru hull is stiff and not collapsing at higher rpm .

And if you have a merc engine make sure the pump is installed right on mine there's a difference . I found out by putting one in wrong on the stbd engine. It'll cool but will not pump enough water to keep up.

something else to check is the impellers that are "in great shape", the piece of impeller you found in the pump housing could have lodged in there and caused the one "in great shape" to spin on the shaft, and it could be pumping some water at lower speeds and then just sit and spin on the shaft at higher speeds.

Since the boat is new to you, start with the obvious (if you haven't already) -- is the shutoff valve at the water intake thru-hull fully open? Maybe previous owner had it closed off at some point and 'forgot' to tell you. Have you been operating in weedy areas and maybe have the intake plugged a bit, or any zebra mussels? If safe to do so where you are, go for a swim with a dive mask, start at the source, and work your way back.

Its it freshwater cooled (closed system with tank), make sure the tank (as well as the overflow tank) is full with a water/anti-freeze mix, and the cap is tight.

Its probably something obvious - many good tips here - check them all to avoid future problems.

I bought the IR temp gun and found that I have a bad engine temp sender. (I switched the dashboard gauges and that wasn't it.) However, i swear there is more steam coming from one engine than the other, but the IR temp gun says the enigine is running the same as the cooler one.

check your transmission strainer,there could be some crap in there.happened to me,i clean them every couple of weeks

If there is a trans strainer I will figure out where it is. But just checking that you weren't referring to the raw water strainer right after the seacock.

davescarrs wrote:If there is a trans strainer I will figure out where it is. But just checking that you weren't referring to the raw water strainer right after the seacock.

seacock-hose-impeller pump-hose-trans cooler(long skinny, prob bolted to motor mount or manifold) hose to top of intake manifold. when you take it off the inside is like honeycombs, it is prob 11 inches long and 1.75 inches wide. trust your ir gun, check your grounds on the engine, I'm kinda new myself but check for the fiber gasket on the sensor before the wire, if you are really ambitious swap out the sending units and washers nuts etc.

Davescars, did you compare temps on all exaust hoses right where they exit the elbows?

I've already noticed that the fiber gasket on the engine that i thought was running hot had a tear in it. I switched the nut, washer, etc with the other engine and still get a hotter temp reading at the dash gauge een after the switch-a-roo. I will check the other stuff as suggested in this thread. Thanks for the help. I appreciate it.

I changed the impellar and impellar cam before buying the IR temp gun and finding that both engines appear to be running the same temps at the sender. The steam still bothers me.

I will try what Big D says and "compare temps on all exaust hoses right where they exit the elbows"

Thanks again for the suggestions!

Thanks to all. All sounds like good advice... but I may have figured it out (I hope)....

I went out today to change the thermostat and proceeded to take apart the by-pass and flow-thru hoses from the thermostat housing. The by-pass hose (that goes directly to the exhaust risers) is completely deteriorated along the bottom and the inner lining had completely plugged the hose! This would mean that no matter how "open" the thermostat was, the flow would ALWAYS go thru the engine. Basically, it would be like running without a thermostat...that's why it would run soo hot and running steam in the exhaust (at least one reason for it)... I checked all of the other hoses by "feel" and found no issues. I figure I will replace the de-funked hose and see whare that leaves me.... and trouble shoot beyond that if needed.

I'll post a pic of the "de-funked" hose when I get a chance... Maybe somewhat common to you "boat engine" people, but from a "hotrod" car guy, I've never seen anything like it!

Thanks,
T Dave