Melted Guide tube and blistered upper water pump housing.

[jwestjr]

Hello iboat forum friends, I recently bought a 1972 Starcraft Starchief and have problems with it running hot. I ran it for 8-10 hours but watched the guage and kept it low enough to not ruin the engine. I pulled it home and noticed some oil dripping form the water inlets. I dropped the bottom or lower section to look at the water pump. The guide tube had melted so much it looked like a cloth rag draped over the water pump. The upper housing of the pump was blistered also. Was this done by running the engine out of the water or some other cause?
120 mercruiser w/ 120-140 outdrive.

 

[figaro]

to melt the plastic guide tube must have required some good heat .. exhaust shutter break apart and get stuck preventing exhaust from exiting drive freely ?

 

[Bt Doctur]

worm impeller or clogged riser

 

[jwestjr]

This is my first IO, have a lot of learning to do. I didn't know it had an exhaust shutter. Is it located in the exit of the exhaust manifold of the engine?

 

[jwestjr]

Well I guess it would be in the drive.

 

[Bt Doctur]

shutters are normally in the Y pipe or exaust pipe, Impellers are good for 2 years so if your more that that its probably your source to overheat.Check the oil level in the outdrive, too low and you can destroy the drive.
You should never run the engine with the drive attached without a water source.

 

[jwestjr]

I have ordered a couple of shop manuals but they haven't arrived yet. The elderly gentleman that had it kept the boat in the water all of the time in a covered slip/dock. When we test drove it he told me to keep a good eye on the temp guage but it never ran hot then. I guess he knew something. He did tell me it was best to keep the rpm below 33-3500 rpm. Now at about 2500 is max before temp starts rising. I also saw today a couple holes in the exhaust bellows. I don't know what factor that has on it.
It was low in gear oil. I drained it and put new oil in before I took it out the last time. Since then there is oil leaking out of the water inlets of the foot. Where the shift shaft is located is where most of the oil was. Guess I need to break the upper down and replace the seals.

 

[stonyloam]

The water pumped by the impeller does TWO important things. It cools the engine and just as importantly it cools the EXHAUST. Yeah you did it. The engine may have not gotten super hot, but the impeller did not circulate enough water to cool the exhaust, and the hot gasses melted all of the plastic. You need a new complete pump housing and impeller and water pocket cover. You used to have shutters in the exhaust, there is almost 0 chance they have survived the heat. When you replace the water pocket cover, watch those screws, if they break you are....... Well screwed. Good luck!

 

[jwestjr]

Alright, not the best way to learn but a lesson well learned. I picked up a new pump kit but it didn't have the bottom part, just the upper shell with the impeller cup. I will get the bottom piece soon along with the other new parts.
Thanks Terry.

 

[stonyloam]

I would take a good look at the water pocket cover. You might be able to check it for leaks by hooking a hose to the copper tube and plugging the outlet. If it does not leak you could leave it. Judgement call.

 

[jwestjr]

I looked at it with a flashlight. I couldn't see any blistering or signs of extreme heat. I did seek professional help. A mechanic is going to pressure test it for me and pinpoint the oil leak as well.
Thanks again.





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[jwestjr]

The mechanic I have talked with seems to have a problem working on the inside of a inboard/outboard, just the outside of the boat. My question is can you install a new exhaust shutter from the outside of the boat?

 

[achris]

can you install a new exhaust shutter from the outside of the boat?

No. You need to remove the exhaust elbow from the manifold then the rubber boot from the top of the exhaust pipe. The shutter goes in there. If the mechanic didn't know that, find a new mechanic.

Chris.......

 

[jwestjr]

Thanks Cris