johnston seahorse

[johns]

i have one of these engines which overheats ,i have checked the impeller which seems fine ,some trickles of water come out from two holes just above the water line with the exaust is there somewhere else it should be coming from ?apart from this it runs great all help welcome

 

[clyst]

Hi John. You don't say if you've checked the thermastat always a good bet. Failing that try reverse flushing back up thro' the leg or if you've access to an air line a blast of air back up thro' the telltale out let sometimes works .

Hope the above is of some use to you .

Fair winds. Terry

 

[andy_wilson]

Which model / hp is it?

Depends upon the model. Mine has a vent above the water line out of which cooling water splutters. It is not a huge flow, the rest is ejected at the exhaust port (above or through the prop.).

Thorough and persistant rinsing in hot fresh water is the best I can recommend. If the thermostat housing is easy to get you could check it, but usually they fail safe i.e. open.

IMPORTANT

I do not know the internal layout of the powerhead, but on the basis that it is a wet exhaust I would say do not use an airline to blow back through the system unless you are absolutely sure there is no residual water anywhere in the system. Given that the only way to guarantee that is dismantling, it's a no-brainer anyway.

Another thought.

Have you got the slow running jet adjusted correctly? Most OMC motors have this adjustment to eliminate a lumpy ride at low to medium rev's. Usually found on the front of the engine cover, marked like a volume control. If it is too rich, starting may be OK but once warm could cause the motor to choke itself to a standstill.

 

[Guest]

I have a Seahorse 4 twin ....... took it to a OBD service agent .... I have same problem .... and mine definitely overheats !

Got the same response from them as I had from others ..... typical Johnson ! They said OK they could sort it, but advised that the price is high and they offered advise on DIY .....

Now some would say that maybe they were being 'awkward' ---- far from it, they in fact spent time explaining why they would advise me how to do it ..... basically that its an engine that will suffer this problem again and again and again .....

So I was told to disconnect the power head and then air-blow out the leg channels - BOTH ways. Then to check all waterways in the power head which are most likely blocked, blow them out or even 'poke-em' out ..... but eventually it would need a strip down ..... They advised to NOT blow through before disconnection head from leg.

I am now looking for a Johnson 4 Workshop manual etc. Seems a shame to waste the engine !!