Dumb Question about freshwater coolant

[Breakin Away]

So I suppose these are all signs of an over sized Prop...

It's over-pitched, not over-sized. A prop shop can adjust the pitch of your current prop, although going from 12" pitch to 9" pitch may be more than they are able to do. You might want to inquire about this before launching this spring.

Note for others: Never purchase a prop with larger diameter than the factory spec. Its clearance with the hull is carefully engineered, and an oversized prop may cause vibration, cavitation, or worse.

[Ron Hill]

Guys : The Michigan Wheel "sailor" props have a much larger cord (& surface area of each blade) than the Catalina Sailor props made in Australia. So It's impossible to compare them, so I'll guess that "Breaking" is correct - that you are lugging down the engine.  You need to get a picture (or an actual prop from a friend) of a Catalina Sailor prop and take them to a prop shop and see if your Michigan can be down pitched to match the resistance produced by the 3 bladed Catalina Sailor??

The best prop shops will have  "Prop Scan" capability!!

A few thoughts

[pbyrne]

I had this situation in the spring after winter.  Some coolant in the bilge, and the overflow bottle was dry.  During the warmer months, engine had coolant and so did the overflow, normal operating engine temp.  Turns out the fix was 2 things. 

1 - new engine coolant cap
2 - new coolant hose towards the bottom of the engine

My guess is that the coolant hose, after 23 years next to the engine got more heat than the other hoses and deteriorated.  It was showing hairline cracks.  Over the -20 C winter months, my guess is that the hose contracted and over 5 months on the hard the coolant leaked.

The changes above stopped the loss of coolant over the winter.

Coolant cap, may or may not have been an issue, but cheap (and very easy) maintenance as it has a gasket in the cap that fill fail at some point. 

Other than tightening all the hose clamps, I would see if you can inspect the condition of all the coolant hoses.  Some run to the water heater... which I'm working up the courage to change...

Thanks Jim. That's what I've been doing, but the engine runs hot and the expansion tank always seems dry.

So, I read one method for burping the system which involved watching the flow into the expansion tank until no more bubbles appear. Seemed to imply a cold system. That got me wondering if the expansion tank should normally have coolant in it even when cold. Hence the dumb question!

[Ron Hill]

pby : I like to use a clear hose from the engine to the coolant recovery bottle.  That way I can see that there shouldn't be any bubbles in that line!! If there are - I don't have a closed system!!

A thought