Engine overheating

[cterry]

Hello all.
I just came upon this forum and it looks like a great place for an old boat head like me. I am not a boat builder, but I have done extensive restoration work on 2 Skiff Craft's including hull and deck and structural repairs repairs and know my way around these boats pretty well. I live about 30 miles from the Skiff Craft plant in Plain City and have spent many hours there, have worked on my own boats right in the plant and have become friends with the Bill Berrisford, Steve Fry and Henry Stutzman, the "main men" of Skiff Craft.

I have a problem unrelated to boat design, but I sense that there is some expertise which might shed some light on this.

I have an early 70's 188HP (302 Ford) Mercruiser Model 288 - I drive setup in a Skiff Craft 26' SFFB. . My cooling system is the standard sea water only version. I recently did the water pump rebuild (in the gear housing) and replaced the thermostat in the hopes of correcting an overheating problem which didn't effect a fix.

My temp gauge doesn't have any measurements on it so I can't say what this means in terms of actual temperature (operating range for my rig should be 140-160 degrees), but it is running up about 1/8 of an inch from the red. If I sit at idle for a while, it will cool down and run right in the middle of the gauge, but the temp will immediately start climbing as soon as I'm under way. It's never went in the red, but it seems way high compared to previous years. The circulating pump is not making any noise and seems fine.

Would this have anything to with the exhaust system and if so, what should my course of action be? Should I clean the elbows? Do the temperature sensors themselves ever go bad thus giving false readings? Is it possible I have obstructions in the cooling path and if so how could those be attacked?

The engine runs like new and doesn't seem stressed about it's operating temp, but I don't want to chance it. I'm just not sure what to check next and I don't have the funds to submit to exploratory surgery by a a mechanic.

Amy help would be much appreciated!

Regards to all, Chuck.

[Willallison]

I won't pretend to be an expert on the subject (especially as I've just put a new engine in my boat after cooking the old one! ) but there are any number of things you should look at:

Thermostat - check it's opening at the correct temp and that it's not rusted up.
Temperature sender - it may just be the guage playing up.
water jacket - in older raw water cooled engines the passages become progressively blocked over time. Same with your exhaust risers and elbows.
Water circulating pump - might sound ok - but check the flow rate - and do the same with your water pump.

There's more, but that's where I'd start...

I appreciate the sound advice. I am going to start checking these things out. I suspect it is in fact restrictions in the system. Hopefully I'll be able to open it up.

Regards, Chuck.

[cterry]

I accidentally posted a reply as crterry instead of cterry. It's really just me and not Jeykle and Hyde.

Chuck.

[dpearce]

Hi there:
I checked with two Skiffcraft owners here in Minnesota and couldn't find advice to your question.

That said, wanted to let you know of a Skiffcraft website we started. Check it out when you get a chance.

Dave

www.oldskiffcraftboats.com

[gonzo]

Corroded risers and exhaust manifolds will restrict water flow and overheat the engine. Also, in an engine of that age with raw water cooling, the water jacket is probably corroded. You can remove the freeze plugs and clean the passages.