Black max overheating!!! Can't figure out why.

[fastmike22]

I have a 175 black max that has me stumped. Last summer it would run cool until I got it on a plane then it would heat up quick but cool down soon as I let off the throttle. I put a new poppet valve in this winter now it's getting hot at low rpms. Put the old poppet back in and it's still the same. Had 8-10 psi at idle and seen up to 25. I switched out the impeller and housing because it was 2 years old. Now I'm getting 20-25 psi at idle and 30-35 just over idle and its still overheating. Confirmed by the alarm. I had the boat backed in the river to test not the ear muffs. Checked t-stats both opening, compression was 115-125 on all cylinders and pumping water out the p hole. What should I do next? This is my first boat so it's pretty new to me. All the local shops are swamped so I'm trying to fix it myself. Thanks for the help!!

 

[Big Fish Billy]

Re: Black max overheating!!! Can't figure out why.

Wondering if some sort of "mouse blockage" could have gotten in over the Winter. Certainly seems like it. Next guess would be a head gasket leak, you could try backing off the torque on the bolts and retorquing in a 4 step process. Check the poppet to make sure it's loose and working. I'm sure some other guys will report in with ideas....

 

[Dukedog]

Re: Black max overheating!!! Can't figure out why.

That kinda pressure, especially "after" tha poppet deal, says ya got something screwed up. With any kinda overheat condition I recommend ya start with a "complete water pump kit" first thing. Just cause something "looks good" don't make it so. Make sure T-stats are clean and work right. Poppet is usually pretty finicky. Everything with it has ta be clean and installed right. Best to install new and right. Those kinda pressures indicate a blockage somewhere and would think it has ta do with tha poppet reinstallation with what your sayin'.......Coolin' parts are cheap and nothin' ta skimp on when ya consider what their job is....jmo

Have ya got a manual? Not one of tha after markets, a real one?

 

[fastmike22]

Re: Black max overheating!!! Can't figure out why.

I did install a complete water pump kit with new upper, Lower housing, impeller and gaskets. I ordered the poppet via my serial number and some if the parts didn't fit. Any way of trying to flush the engine before I pull the heads? My engine doesn't have the water hose hookup on it. Probably gonna try another new poppet valve also

 

[Chris1956]

Re: Black max overheating!!! Can't figure out why.

That is a lot of pressure for a Merc. You might check compression to see if you have a leak into the cooling system.