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1988 Mariner 40 hp - does it have a thermostat?

Floydha

Member
I've noticed that the 'pee stream' starts flowing within a few seconds after the engine is started. Does this engine have a thermostat and if so, where would it be located. I'm thinking if it DOES have a thermostat, it's stuck open or the previous owner may have removed it for some reason. I've poured over the SELOC Repair Manual and can't seem to find one shown.?? The engine runs fine as it is, idles a little rough at 800-1000 rpm, runs well, starts easily -- really can't ask for more.

Engine stats (compliments from "Haventaclue" from my 8-25-10 response to my 'what year is this' thread).

1988 Mariner (Yamaha build) 40 Hp ELO
SN: 6E9 430989

Thanks for your time.....

f.
 
Thermostat is located under the cover directly above the top sparkplug (cover kinda looks like a figure 8 on it's side). There is also a poppet valve under that cover (a kinda poppet - not like on modern Merc's - looks more like the thermostat in your car - called a pressure relief valve back in the late 80's).

On this particular model the tell-tale is getting it's feed from the exhaust plate (where the water first enters the powerhead), so it's "normal" for it to start flowing as soon as water makes it to the powerhead (the water channel in the exhaust plate feeds the channels in the powerhead itself).

On the downside of this particular design, while it tells you the water pump is working fine it doesn't tell you if the water is getting past the thermostat or circulating properly through the powerhead.
 
Mr. Graham,
Thanks for the reply... it makes sense. I've had no problem with overheating but was worried that it may be running too cool. The only way to know it there is a thermostat actually where it's supposed to be is to open her up and check. If there isn't one .... well, I'll put one in. If there IS one I'll put it into hot water to see if it's working properly. I'll be able to get to it this weekend and I'll report my findings back. Thanks again.

f.
 
Just pulled the thermostat and put it in a pot of water on the stove.... it opened at around 140+/- deg F. Guess all is working the way it's supposed to. That's a 'thought' that's off my mind now. Thanks Graham.

f.
 
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