wrote in message
...
On Sun, 18 Mar 2007 08:55:47 GMT, "will_456"
wrote:

I have a Mariner 8hp which overheats after about 10 minutes. The tell-tale
stream turns to steam and the engine stops shortly after.

I started at he bottom and checked impeller and pipe up to powerhead all
working fine - good stream at idle and for about 5 minutes at high rpm so
I
think the water flow is ample but engine gets hot and it can't cope.

I have taken off head and checked passages, ditched thermostat and
removed
grit from water jacket around cylinders.
Some aluminium has chipped off around the sleeves exposing the actual
sleeves to the water. Could this be what heats the water up to such a high
temperature?


You may have a problem where the tube connects to the power head. Have
you checked the water pressure? "T" off the telltale hose. It should
be 15psi or so at WOT. If it drops to 3 or less you will overheat,
just not enough water to do the job.

May be a problem at the bottom of the tube, not the power head. There is a
rubber donut the tube goes into at the top of the waterpump. May be split.