Mercury mariner

Apologies, I've had a few of these and I've been lucky enough to have the variants which didn't have thermostats, but I see now in block configuration #2 under my s/n there is a model variant that has a t-stat.

That thermostat recently "tricked" me on my '98 Merc 25EH. I had very low water output from a wasp free pee hole. Upper cyclinder got too hot to touch, running in a barrel. Since I have had the motor for over 10 years and not changed the impeller, figured that had to be it. The impeller had no broken vanes and they were still relativey flexible. I did see some wear on the housing and short output hose had some cracks. Got it all back together, and flow didn't improve. Thought I messed up with missing the tube. Took it apart again, and as far as I could tell, was aligned. I finally just removed the thermostat, and walla, nice stong flow. There wasn't time to order and receive stat, so took boat to camp and ran without it just fine. The new 120 degree stat arrived and will install next time. It is a simple two minute job. At least the agrevation encountered will help drive that mistake into my memory.

Bign0703 said:

Ok guys. I'm in a pickle with this thing. Replaced the entire impeller assembly along with the water tube seals and she won't pump a drop. I've heard several say these motors have to be submerged to pump and won't pump off a hose but don't know for myself. I plan to dip the lower into a tank and running it with a drill to see if it is pumping but anyone have any idea what could cause this. When it's on a hose it acts as if all the water is flooding the mid section but not going through motor.

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You missed the hole.

Oh yes. I finally got it lined out. The upper seal and base gasket were shot! Got them replaced and she runs as good as new now

Pappy said:

By the way, when you are running in a barrel or bucket the water level has to be a few inches above the parting line where the gearcase meets the exhaust housing. That will insure your water pump is fully submerged and capable of pumping.

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