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Yamaha 150 overheat alarm

N

northernwoodw

New member
"I changed the 2 thermostats a

"I changed the 2 thermostats and the impeller, pump. Yet on the way back in from fishing ( only end of trip never at start or 1st 2 hours of day)
the engine lately like clock work will alarm and start to loose pressure. I have the boat for 6 years engine is 150 2 stroke. I always have flushed it with fresh water and never had a problem until last 5 or 6 trips. The first time i ran through some sargassum weed when it started to overheat. Sent the boat in immeditaly for work. Also in 6 years it never did that even once. What could be the problem, could their still be stuff stuck in there, and if so how do I get it out. Please help very frustrating Thanks"
 
"I have recently struck a cons

"I have recently struck a consession of Yamaha outboards with similar cocerns to yours. After replacing t/stat and water pumps, i found in all 4 cases, yes 4, that the water tube from the pump to the lower end of the power head, was corroded where is has the rubber grommet around it. It is nessesary to remove the g/box and lower leg to replace this pipe, but it is not a difficult nor time consuming repair.
Hope this may help."
 
"Could be a bad temp sensor on

"Could be a bad temp sensor on the engine, acting up when going thru expansion and contraction (from heat) of running, stopping and restarting the engine. Any time I've had the heat alarm go off there is always a noticable amount of steam from the exhaust, confirming it is actually hotter than the normal operating temp."
 
"I have a 1994 Pro-V 150 that

"I have a 1994 Pro-V 150 that I bought in 2000. Sense I've owned it the overheating alarm has gone off periodically when trolling at low speed or idling for longer periods of time. It can take anywhere between 5-30 minutes before engine will run without alarm going off, and then is fine again. I've replaced impeller, t-stat flushed system on a regular basis and still having problem. I will check into what Jon posted, but if that is not the issue, I would love any other possible solution's. One last thing has anyone heard of Yamaha Motors addressing this issue. It sure seems to be a big problem with this era of motor."
 
"G'day TR, Mate, Ive only

"G'day TR, Mate, Ive only even struck the pick up tube/grommet corrosion on 50/60 hp models, and that was low speed operation. As Im more of a Honda tech, i do have a few yrs of Yamaha experience. The inspection/have a look process isnt to hard.
First, remove the g/box assy.Then any fasteners that may hold the lower cowling. This will include the lower leg to pivot mounts. Once the exhaust trunk is exposed, how many pieces/condition of the *pump/power head* pipe ?
If this tube is not corroded or damaged in any way..........i will need to put my thinkink cap on..............Im in Nth Australia. we get stuff here that NO where in the world gets, salinity levels vary massivly ! I just like to offer ANY insight i can.
Lemme know how you go, i may surprise with an Aussie fixit."
 
"Thanks Jon, I appreciate your

"Thanks Jon, I appreciate your input. This web site and people like yourself are a great asset for motor dopes like myself. I actually fixed the problem. Somehow when I replaced the impeller and checked the pump the first time (reference back to being a dope)I missed damage to the water pump housing. the plasic housing had melted slightly where the water intake is causing just enough restriction to have my problem. After replacing the housing all is well."
 
"I just purchased a boat with

"I just purchased a boat with a Pro V 150 Yamaha outboard (P150TLRQ). It had a jet pump on it and I don't care for it much. I took the jet pump off and am trying to put a new water pump kit on the lower unit. I have not been able to find a decent exploded view or instructions on how to put things together. The pump kit is complete, except I need the rubber gromet for the water tube, May be able to take the one off the pump on the jet pump, if I get that far. There were three thin washers (one wave type and two flat), and a white nylon split bushing with an aluminum cap on the shaft of the lower unit. I don't know how they fit into the scheme of things. Any help would be appreciated.

Thanks"
 
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