88 150 mag II overheat @ 3000, water pressure

[ronnieboy]

Been to lots experts, no help, water pressure jumps wildly up and down from fast idle to wot, if below 3000 rpm, gage says 7 pounds, and gets hot, wot goes to 15 pounds and stays cool all day, fast idle always gets hot, installed new water pump kit, and visualy checked poppet, no visible damage, thermostats work good, can blow air with mouth through telltale without restriction, comes out excess water dump and exaust in prop, this is a 1988 mariner mag 2 150, great compresion, no carbon, . whats next? ron

 

[andy6374]

Re: 88 150 mag II overheat @ 3000, water pressure

If you haven't ever replaced the poppet valve assembly components or tstats, its overdue. If the poppet is stuck open it will cause the overheating condition at idle speeds you are talking about.

 

[ronnieboy]

Re: 88 150 mag II overheat @ 3000, water pressure

poppet wasnt stuck, i dont think its seating against block, tstats were replaced recently, i also retested them for opening. seems like its got a lot of air trapped in the top of motor.

 

[ronnieboy]

Re: 88 150 mag II overheat @ 3000, water pressure

thanks andy, got new poppet assem commin from merc parts express, hope it helps. should there be some restriction when blowing through the telltale?

 

[andy6374]

Re: 88 150 mag II overheat @ 3000, water pressure

Originally posted by ronnieboy:<br /> poppet wasnt stuck, i dont think its seating against block, tstats were replaced recently, i also retested them for opening. seems like its got a lot of air trapped in the top of motor.

If the poppet isn't seated it will dump water out the exhaust. At idle speeds there isn't enough water pressure to fill block if the poppet is open.

 

[ronnieboy]

Re: 88 150 mag II overheat @ 3000, water pressure

thanks andy6374, will advise after installation, i appreciate the advise. later ron

 

[ronnieboy]

Re: 88 150 mag II overheat @ 3000, water pressure

parts still backordered, realy like this web site , has lots of info ,

 

[ronnieboy]

Re: 88 150 mag II overheat @ 3000, water pressure

well guys, poppet and waterpump didnt help, still getting fluctuations in pressure gauge while running, dont get hot while idleing, just at half throttle, dont get hot while wot. now what? bout to give up and buy new super evinrude! maybe it wont get hot! at ropes end,

 

[andy6374]

Re: 88 150 mag II overheat @ 3000, water pressure

I think what you are describing is normal. Right around 3000 RPM's you will see fluctuating water pressure readings. This is the poppet opening and closing. But at planing RPMs, I don't really know for your boat but, but say they are 3500-4000 RPM's it should run warm but not overheat. The faster you go the more cooling water.

 

[ronnieboy]

Re: 88 150 mag II overheat @ 3000, water pressure

thanks andy, motor still gets hot slowly over 2500 to 4000, then cools quickly at 5800. was wondering if poppet spring is weak, thinking about shimming with .020 shim, and trying again to see if pressure changes, maybe , poppet is unseating to soon, what do you think? i noticed that poppet has more pressure when screw is loosened a little, seats harder. dont know what to do next. any advise? thanks ron

 

[andy6374]

Re: 88 150 mag II overheat @ 3000, water pressure

Well if you are going to remove the housing bolts to get to the spring, you should probably just replace everything else while your are in there. The more you torque the screw, the more it compresses the spring, resulting in an increased spring force and thus the "more" seated the poppet is and the more water pressure required to "push" it off its seat (the grommet).<br /><br />It should open right around 3000 though, give or take 200 RPMs.<br /><br />Go easy on taking the housing bolts out. Last time I did mine I pulled the threads out as well . When reinstalling the bolts coat em' with some mercury 2-4 grease or some perfect seal.

 

[ronnieboy]

Re: 88 150 mag II overheat @ 3000, water pressure

hi andy, well i fixed the problemS, turned out to be 3 different things. first, the poppet spring was weak, merc tec said it needed to be between 5 and 9 pounds preload, shimmed mine with extra spring retainer washer, to 5 pounds, then found that upper water tube seal was scratched and leaking, allowed exaust to fill water passages in heads, small glob of blue silicone sealant sealed great, Last, when i was looking for my stored extra parts, i found a receipt from merc, water pump was 4 years old, felt stupid for not checking sooner, just seemed like last year,ahhahhahh , i guess thats what happens when i get older, (50+)memmory is the 2nd thing to go, hahahah Motor runs like new, idles at 3 to 4 pounds water pressure, thanks for your help, will try to return the favor ron

 

[andy6374]

Re: 88 150 mag II overheat @ 3000, water pressure

ronnieboy-<br />Glad to hear it and I'm only glad I can return the favor to others here at iboats. I have been helped and learned so much from the people here.<br /><br />Good luck!