George,
I recently helped a friend bring back a 1989 Newport 30 (about a 125 mile trip). The boat was equipped with a 25XP universal. The older model had the compression release option.
3 hours in, about 10 miles offshore, the boat filled with steam. We used the headsail for steerage to identify the cause. What we discovered was coolant was steaming out from pinhole leaks in the vertical tube to the pressure cap on the exhaust head.
I had never seen this before and upon further checking, saw no overflow bottle, just a hose to the bilge. I believe there was the possibility of steam & pressure over time etching the copper tube and eventually causing these pinholes.
I've have been designing piping systems for years and know steam/pressure can cause etching in certain materials, such as copper.
Without a sealed-in system (an overflow bottle will seal out air), I believe the problem was two-fold.
1. An overflow hose to the bilge will cause a loss of cooling fluid after each engine use and allow for air in your exhaust head and thermostat housing.
2. I believe the absence of a bottle caused the eventual failure of the pressure cap copper tube @ the exhaust head. No telling how many times the orig. owner overheated his engine, and checked his fluids. Remember the dumbest guy you will ever meet is the guy you bought your boat from.
We did get the boat back but my pal was not a happy camper. He ordered a replacement head ($1800.00), and we changed out the old one. We also added an overflow bottle. We started the engine, put it in gear and ran at 3/4 cruising speed for 5 minutes.
The overflow bottle had coolant under pressure filling it and it was boiling. What we found was the original owner had removed the thermostat, there was none. I have heard of folks in warmer climates doing this but it will change the operating temperature parameters of the engine performance.
My take is that there may have been a correlation between not having an overflow sealant system, and because the engine was running hotter, the orig. owner listened to a dummy and removed the thermostat. I also think over time this combination caused his press. cap tube to fail.
Why do all cars have overflow bottles, & thermostats, think about it.
We also cleaned the heat exchanger and are going to sea trial the engine today.
These are just some thoughts I have for saying to be smart, hook a bottle up and run at the correct operating parameters.
CR
