Re: QD19 running a little hot?

[orpilot]

Hi Beerman,

I’m curious how many hours you have on the motor? Typically, hot running motors in your situation (right after new rings) stem from the heat generated from the cylinder-ring friction. Having overhauled a few hundred small outboards, I can relate a little of my experiences on how to avoid the problem. First off when honing the cylinders get your hands on a cylinder hone with the little carbide balls instead of stones. They leave what’s called a plateaued finish that creates a better seal with a lot less friction and a much shorter break-in time. I almost always replaced pump arts when doing an overhaul but I can tell you that for your vintage motor the pump housing usually accounts for the most loss of water pressure. If you have any depression in the pump housing surface (where it meets the impeller), replace it.

Back to break-in. First, run a richer mixture of oil during the 1st tank. It’s best to do initial running in a test tank with circulating water, first with lower RPM’s and then once every 30 minutes, bring it up to full throttle for about 30 seconds. Engines that have cylinder walls honed with stone type hones typically take about 6 to 10 hours to break-in and will run hot until the rings seat… usually less than a couple of hours if you’re using carbide ball hones. If your break-in occurs on a boat, run with the lightest possible load, first at the lowest speed that gets the boat on a plane. Avoid running it plowing through the water. Reach back and check water temperature from the exhaust housing. Let it run at a fast idle to cool down if it’s getting too hot. Don’t let it get so hot that you can’t hold your hand in the outgoing water flow.

I’ll assume you resurfaced the cylinder head and you have new gaskets there and on the exhaust cover. Leaks in either place can disrupt water flow.

The ’58 10 HP like you have is a great motor. I’m sure you’ll get it sorted out but I have to say that if you don’t have close to 10 hours of break-in time you may be chasing something around that’s going to go away when it gets some more time on it.

Jim