Engine Temp for a 351

Yeh. 120 is too low. It could be faulty sending unit but my guess is it's time to change your t-stat.

110 - 120 is low. My 1986, 351 runs between 160 - 170. My old 1980, 351 ran about 160. The plugs won't burn as nice if it's running cool. How's the thermostat? At least you're not overheating!

dmoney, mine did that when I first acquired the boat. The problem was the raw water pump was worn. With the boat moving pressure would force the water up to the raw water pump where it would begin to pump. The raw water pump did not have enough umph (pronounced ooommmppff) to prime itself. After water reached it (from me driving the boat or gunning the engine) the pump would begin to work. Until then the engine would overheat but as soon as I began to drive the temp would fall to normal. An impeller replacement did not fix it. I had to polish wear grooves out of the body and replace some kind of bronze part, that came in the complete rebuild kit, and fits into the pump cavity. I think I bought it from skdim. I had to dissasemble my pump to find some numbers stamped on the flange which the seller could use to match up to the correct kit (my pump is a 1968 vintage and parts are still available for it.)

(But nms1991 may be right on - it sounds like it could be a air leak.)

I have a 92' Ski Nautique that I finally got out this year (wife just had a baby!). Replaced the impeller last year, but it still seems to be running oddly temp wise. When opened up between 28 and 35 mph, the gague reads between 160 and 170. When I was idling or pulling into the lift, it moved up over 180 and approached 200. Any ideas? Thanks.

Thanks.... That's exactly what mine does. The temp seems to register very high (around 180 - 190 degrees) after it first warms up and then quickly drops back down into the range where it begins cycling up and down. I was suspicious of my theremostat (but not suspicious enough to pull it).

I do not use the boat on salt water, just the Fingler Lakes in NY.

My temp does not move after warm up.

It depends what temperature thermostat is in your boat. I've got a 160 deg. stat in my '79 (original equipment was 140 something), and mine runs 160-170.

I believe your boat originally would have also had a 140 stat, either way you're running too cold. Replace your stat with a new 160 stat, skiDIM has them.