Join Date: Jun 2009
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Removed thermostat from outboard. Thoughts?
My 4 HP Yamaha had been running hot. I've never been happy with the little trickle of cooling water dribbling out of it, but was told because it's such a small motor that's what to expect. I replaced the impeller and didn't see any noticeable difference. I started thinking about what else could be causing a restriction in the coolant system so I gave the assembly drawings (from outboard parts websites) a second look. There's a thermostat??? Yup. I pulled the exhaust cover off and saw a very gunked up thermostat. Most of the gunk was clear/white and gooey. I thought maybe it was salt and touched it to my tongue to verify. No real taste at all. Maybe a baby sea nettle got sucked in through the water intake? Either way I don't have a spare $56 (!!!) thermostat laying around and I wasn't about to wait a week to get one so I put it back together without it. Put it back on it's engine stand (a hand truck) and put the bottom end in the test tank (5 gallon bucket) and ran it. God love it, the little bugger started up with the second pull (having sat since Columbus day when it's running-hot problem caused me to drift uncomfortably close to the Carnival Pride)
Healthy stream of cooling water which was coming out warmer than it was going in.
I use the motor for 2 minutes to get off the dock, and 2 minutes to motor back to the dock when sailing. Once the Chesapeake gets warm I throw it on a little aluminum rowboat and use it for crabbing. 8 hours of half throttle for a minute, idle for a minute. Little bugger uses a gallon and a half doing that from before sunrise to early afternoon.
Do I even need a thermostat? Even today in 40 degree weather it ran fine in the test tank. (and on some year-old gas from my stash of pre-ethanol stuff)
I can't see how sucking 70 degree water on a 70 degree day will do any harm, and I don't think 2 minutes of sucking 50 degree water in April will make a difference. I've torn enough scorched pistons out of weedwackers to know that heat is what does these in -- taking longer to warm up (or not warming up at all) doesn't seem like nearly the problem. At the recommended 100:1 mix I doubt it's going to foul out the plug real quick, but I carry a spare and a wrench just in case. (I've never needed them, even with the first two seasons I had the thing not ever running more than half throttle or more than five minutes.)
Why even put one in there? Maybe duck hunters running around breaking ice with their little Jon boats would benefit from a little restriction in the cooling system? I suspect the EPA was happy to see it there to allow it to warm up and properly burn off some more hydrocarbons. The lifetime total gallons I've ran through the little bugger is less than one tank of gas in the tow car so I'm not really concerned about that.
Keep the expenses low and the good times high.
PA Freshwater / Chesapeake