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Bout Time 1

97 yamaha Pro V 150 overheat issue

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Lately I ‘ve been getting the overheat alarm and then Limp mode only at high RPM, like close to WOT. If I shut it down, wait 30 seconds and turn the key on, the alarm goes off and I can run all day under 4500 rpm. I started out by changing thermostats,  checking the poppet valve (old style) and cleaning it. No change. Recently put a new water pump in. No change. Checked both thermo switches per the repair manual. They are both good. Pulled the heads and checked all water jackets. Some minor blocked areas but have always flushed with ears with fresh water after running in salt. Heads looked pretty good. Cleaned everything up and installed new head gaskets. I also installed the new mushroom style poppet valve. I’m hoping I finLly got this solved but cold and rainy here so no trial run yet. Had anyone had a similar problem? Could it be the poppet valve? I swear the old one looked fine. Thanks. 

PS  this engine has 588 hrs on it  

 

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The new poppet is a big improvement over the old style.  Yamahas are very sensitive to blockage in the water jacket passages.  I plastic bead blast the heads and jacket covers to get rid of all the scale and build up.  I also lap the heads flat again.  Try Mary Kate On/Off in a squirt bottle for the passages in the block. use lots of water to clean it all out.  Hopefully your issue isn't a corrosion hole in the exhaust plate mixing exhaust and cooling water.

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When I bought the gaskets at Atlantic Coast Marine here in Jax I asked about the exhaust plate and the water tube grommet. They said they rarely get that repair into the shop but have done a ton of the poppet valves. I got my fingers crossed. 

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Had the same engine ,same yr.  It is a great engine,  mine finally died of  water jacket corrosion. I never had a over heating alarm.  Mine was kept in water at a brackish water marina.  Hope yours is ok,600 hrs is nothing for that engine.  Mine had well  over 1500 hrs. You just don't that power sound from the 4 strokes.

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Had the exact same issue on a previous yamaha.

Replaced everything without solving the problem. Finally pulled the heads, cleaned up the passages, and problem solved. You should be good to go. Mine looked just like yours, which Id consider pretty clogged.

How did it go?

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Well finally got it out today. Ran it WOT up the ditch and it never overheated. That’s a plus. However the last couple times I’ve taken it out it has been smoking from under the powerhead and today I recorded the leak. Looks like the powerhead is coming off to change the exhaust seal which also has the water tube from the water pump running thru it. Does not leak like this when running at home with the ears on. Just when its in the water. B-O-A-T.....lol

31E1947A-FC65-421C-9CEE-291BAD3219AC.MOV

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Update:

Took my boat to a mechanic here in Jax cuz I didn’t want to tackle pulling the power head. Even though I changed the poppet valve, once he got the powerhead off he found that the other end of the hose from the poppet valve spring assembly was clogged solid. Also the power head gasket was roached. He charged me 300.00 labor and about 60 bucks in parts for the gasket, a new hose and the nipple on the return end of the hose. I think I got off cheap! I should be good for awhile now!! Glad no holes in block or exhaust plate! Dude is a solid fair mechanic! Thanks Chris!!

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in the first picture, the rubber hose with the zip tie was clogged on my 115. I replaced the rubber hose, spring, valve and metal connector that was on the block. I guess salt deposits build up there over an extended period of time. good find!

 

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Yep, I replaced the spring, valve and grommet but not the hose. I however did not check the other end of the hose where it enters the mid section. That’s where the bad clog was. So this time the hose and that return nipple get replaced after cleaning out the clog. 

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Is that spring and valve what everyone is calling a poppet valve? What is its function? Besides clogging with salt deposits and causing us grief? Haha

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6 minutes ago, lurem said:

Is that spring and valve what everyone is calling a poppet valve? What is its function? Besides clogging with salt deposits and causing us grief? Haha

Poppet valve allows cool water to stay in the block while idling or running at very low RPM.  The poppet opens (from pressure) at higher RPM when the flow from the water pump is a lot more.

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14 hours ago, Bout Time 1 said:

Update:

Took my boat to a mechanic here in Jax cuz I didn’t want to tackle pulling the power head. Even though I changed the poppet valve, once he got the powerhead off he found that the other end of the hose from the poppet valve spring assembly was clogged solid. Also the power head gasket was roached. He charged me 300.00 labor and about 60 bucks in parts for the gasket, a new hose and the nipple on the return end of the hose. I think I got off cheap! I should be good for awhile now!! Glad no holes in block or exhaust plate! Dude is a solid fair mechanic! Thanks Chris!!

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Indeed you got a fair deal there!  I assume he didn't break any bolts which is rare on an aged Yamaha.  Only thing I may have opted for would have been new upper motor mounts since he was in there. The rubber looks pretty tired. 

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Yeah I asked the same question when I saw them but the picture makes them look worse than they are and since he has not had any broken bolts yet I didn’t want to push my luck. Those mounts could get pricey if a bolt broke and they really aren’t that bad. Have not had any shaking at all. 

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Might have to remove one of the side panels. Not sure but will check when I get it back Saturday. Gonna pick up the boat and splash it on way home to check it all out. 

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Update: my mechanic got the engine back together and I still have a leak. The water leak is coming from somewhere in the exhaust plate. Probably the water tube grommet. It’s all apart again to dig further. Getting more expensive by the day!:( On a good note he has not broken any bolts yet miraculously. 

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Finally got the boat back. Leak was in the exhaust plate. Sand clogged in discharge holes in base plate as well as old leaking grommet on water tube. Good to go now. Just in time for a trip to Rodman!

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Boat running great now had it out several times and have run it WOT with no issues. Glad To have it back right again. All waxed up and ready to ride. 

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