78 Chrysler 20hp water flow

[cwhyle]

Just bought a used 20hp Chrysler outboard and first time out I noticed that water flow out of the exhaust ports was good at low rpms. As soon as the rpms went up, the water stopped flowing out and the engine got hot. It did this in neutral as well as forward gear selection. There was nothing obstructing the water inlet. When it first happened, I was going 3/4 throttle and I saw steam around engine, I immediately checked water flow and saw none. I shut the motor down and then restarted letting it idle and the water flow came back but was very hot water for 1-2 minutes. Any ideas?

 

[eurolarva]

Re: 78 Chrysler 20hp water flow

MIght start with a new impeller. Some 20 HP motors have thermostats and some dont. I would try the impeller first. If that has no effect try taking the thermostat out and run it and see if that improves the condition. You may have a partial blockage inside the motor which might be back flushed out with a garden hose. Does this motor run in salt water or only fresh?

 

[cwhyle]

Re: 78 Chrysler 20hp water flow

MIght start with a new impeller. Some 20 HP motors have thermostats and some dont. I would try the impeller first. If that has no effect try taking the thermostat out and run it and see if that improves the condition. You may have a partial blockage inside the motor which might be back flushed out with a garden hose. Does this motor run in salt water or only fresh?

 

[cwhyle]

Re: 78 Chrysler 20hp water flow

Only freshwater, Minnesota.

 

[Parenouf]

Re: 78 Chrysler 20hp water flow

i have exact same problem i was advised to replace cylinder head gasket which i'm about to do i'll let you know how i get on with it mine had a new imp. and i check for blockages lets hope this fixes it!