Problem with the cooling

[keremulu]

Hello,

I have a question regarding the cooling of my Silver Century. I recently brought it from a chap in my town and had the opportunity to thoroughly test it the past week. The problem is like this: I ran the engine for nearly two full hours at top speed, no complaints, but I noticed that the water outflow was really hot, nearly scalding, impossible to touch by hand. I reduce the motor to half throttle, the water cools down and the outflow is better. Not that I'm saying that at full speed there was no water coming out, but it was visibly less than that of the half speed. But despite this the engine did not sputter or stall at all during the time I was at sea.

I'm still guessing that this shouldn't be the operational warmth of the cooling water?

Any advice would be highly appreciated, many thanks for your time and concern.

Regards, Kerem.

[40TPI]

................impossible to touch by hand............................

You are quite correct. That is way, way too hot! A good outlet temperature is blood or urine temperature... as said by somebody in the Netherlands I believe.

You are likely to have one or more of the following:

a) blocked cylinder water jacket
b) blocked water delivery pipe
c) blocked water pump housing
d) defective impeller

A defective impeller is very much less likely than a) or b). It is the very last thing I would expect if the driveshaft is still turning! It is odd however that there is less water pumped at full than at half throttle. As a rough guide a Silver Century will pump about a litre per minute at 900/1000 RPM and it should be possible to comfortably place your hand touching any side of the motor block. (Careful of the hot exhaust area!) If you can't then then the first thought is a blockage, usually in the water jacket but could still be in the delivery tube. However if one side heats up more quickly than the other sides or is significantly hotter than the rest then that side is rusted up. I mention this since I have noticed that the rust build up is not always uniform on all sides. Top and bottom, particularly on late 40+ cylinders, seem to block first.

Peter

[Hugz]

Possibly less water at full revs as it is working harder and running a lot hotter, as such the water is boiling within the block restricting the flow. Bet there is a lot of steam at the outlet. Probably a simple problem and just requires a backhose.

Hugo.

[keremulu]

Many thanks for your insight and advices. At least now I'm sure that the water outlet temperature is not normal. I was glad at first to notice (what seemed as healthy to me) a thick, full stream of water at 1/2 and 3/4 speeds, but like you say, there is probably a blockage somewhere. Just to add to Hugo's comments, I really didn't see any steam at all at the water outlet, nor was the water spurting out as if coming out from the nozzle of a boiling kettle. That's why I kept on operating the motor, there were no visible signs until I started feeling boiling water drops on my arm blown towards me by the strong wind from aft.

I will first try to perform the backhose trick, then maybe do a strip down of the components. Many thanks for the help,

Kerem.