I have a 2000 fountain fever, bone stock w/502 mags. I replased the t stats this winter and it seams to run warmer than last year, but i could just be wrong! it seamed to run about 170* or so last year and this year the couple of times i have had it out is seams to run closer to 175-180*, i replased the t-stats w/merc 160* that is what they had stock, and both motors seem to run the same temp, also replased the cork gasket? Before one motor since the boat was built and even in the build/numbers sheet fountain gives for your boat one would run a couple of degrees cooler now both run identicaly the same? the alarm has not gone off but just checking before the air and water warm up, does this seems odd to anyone else!

Dude, been there, done that. I have a 32 fever with t502's 1998 with low water pickups. If I get in the same zip code of shallow water it sucks up mud and makes the t-stat's stick. I've talked to a few marine mechanics about flow restrictors, they recommended I get 140* t-stats and drill 4) 3/16 holes in them to let water pass if they stick. have done this for the last 5 years, it works great for me. Also check the p/s cooler for trash,thats where all mine ends up.

I find that MPI motors run pretty consistent temps regardless of water or air temp. Sounds like you have the right t-stats. Maybe your temps senders are going bad?

Does the temp climb if you run it hard?? Does it drop to 160 at Idle, but gradually climb the harder you push it??

If all the normal stuff checks out - raw water pump, strainers, all old impeller pieces removed from the coolers - you'll need to remove the 1 1/4 hose nipple on the inside of the transom plate and make sure the hose isn't collapsing on the insert. It's more common on salt water boats - but you never know.

If both engine temps are the same and staying consistent at all speeds, I wouldn't worry about it. The old Tstats could have been opening a little a sooner with age. My 502mpi's run about 175* on the guages.