175 Mariner running hot

[shorthair101]

I have a 1992 bass boat with a 175 Mariner. Bought this 3 yrs.ago. It ran good then and now. It was and is running about 190-200 degrees when plowing up the lake. When at idle or wide open, runs cool with good water pressure. Water discharge has always seemed week. 1 yr. after I bought the boat I installed a water pump and thermastats but no help. So I'm in the same boat. Runs great except when plowing up Iowa"s no wake lakes. Any ideas ?

 

[achris]

Re: 175 Mariner running hot

There is nothing wrong with the cooling system, it's working exactly as designed. 2 strokes running too cool tend to foul plugs, so the designers of those engines came up with a novel (at the time, everybody's copied it since) method of keeping the engine running hotter at low speeds and cool at high revs. Introducing the 'poppet valve'.... When the engine is running slower the water pressure isn't high, and so the engine is under thermostat control, and they keep the engine running on the warm side, as you see. Once the engine speed is up around 2500 revs, the water pressure is high enough to push the poppet valve open and the engine now has full water flow, keeping it running cooler.

Chris......

 

[Blevins]

Re: 175 Mariner running hot

Yet again i follow chris...and he's right again.... I will offer one bit of add on. Some mechanics will add on a small water impeller just under your cowl on the water pump cooling line that will engage if the motor runs TOO hot. My 98' 225 gets a little to hot as the poppet valve seemed to be going. I replaced the valve but the mechanic advised putting this pump on. He did it for free (as i have brought him lots of business) just to make sure the motor didnt overheat. There is ALOT more no wake zones now a days then there was back then. If you want i can send you a picture of mine.

 

[shorthair101]

Re: 175 Mariner running hot

Thanks for your reply.....Do you think I should rebuild the poppet valve and see if it helps ....I can't give you the revs because the tach is intermittant...thats another subject...anyway, when I am running up to 12 pounds its running about170 degrees,14 to 16 pounds pressure 180 on to 200 degrees. Put it on plane it cools off. Or like you said, its the nature of the beast..................shorthair101

 

[achris]

Re: 175 Mariner running hot

14-16 psi??? Sounds like the poppet is holding up too long. Had this problem years ago with an earlier V6. Ended up cutting a couple of coils off the poppet spring. Solved the problem nicely....