View Full Version : Yamaha 150 hp 2 stroke - Problem
07-07-2009, 02:19 AM
Yesterday I ran through a kelp bed and within a few seconds my alarm came on so I shut down the engine. I assumed that the water intake had become clogged and caused a temperature rise although I did not see any smoke around the engine. I didn't check the temperature of the motor housing but nothing seemed abnormal. I did kick it into reverse before I shut it down in order to see if I could get rid of the kelp. Since I was close to where I wanted to fish I turned on the kicker and fished for a few hours and then restarted the main engine. It started easily. HOwever when I was running back to the dock it would not run up to full power. It would only run up to 3700 rpm and was slow to get up on plane. It did not seem to be misfiring but it did not seem to be running freely either. Any ideas?
07-07-2009, 03:31 AM
check to see if anything got wrapped around your prop spindle - other wise the only place possible to something to have gotten into your engine is through the water intake an d could be clogging it-try taking a piece of thin wire and pushing it up to see if you can find anything
Island Fish Lifter
07-07-2009, 04:25 AM
I cant see how a slight overheat would cause a power loss unless the overheat was more severe than you thought. For sure check compression first. Is it an HPDI model? These units are sensitive to overheat because of the "light" construction.
If comp. is ok, start going through the basics. Is your throttle opening all the way? Are all your cyls. firing? Are you sure it was an overheat alarm? Did you check your secondary oil reservior under your cowling? And by the way, checking the temp of the cowling will NOT tell you if the units hot, you have to remove it then check the temp on top of each head with your hand. You should be able to keep your hand on the surface for a few seconds.
Fill the dam tub!
07-07-2009, 04:30 AM
Oil reservoir full ?
some motors will sound alarm if the tank gets too low
which also may limit rpm's
07-07-2009, 06:44 AM
Oil reservoir is 3/4 full so that is not the problem. I did notice however, that all of the paint on my prop has worn off. I have had the prop repainted and refinished recently and I was suprised yesterday to see all of the paint gone from the prop when I lifted the motor out of the water. Maybe something was caught on it which wore off the paint.
I will pull the prop off and see if something is wrapped on the shaft.
07-12-2009, 04:36 AM
Might have something stuck in the thermostat that was sucked in through the intake. This keeps the thermo open and the engine runs as if it being choked. Try tying your boat VERY securely to a good dock , fenders on , and putting the motor full forward and full reverse. If you are not comfortable doing this you can do it in open water as well.You can ofton see the debris shooting out.
The other possibility is you were in "guardian Mode" the engine restricts the rpms after a overheat to protect itself. You need to shut down the motor and power to reset.
Let us know how it goes. Good luck.
07-12-2009, 03:48 PM
It won't be protection mode because it keeps the engine under 2000rpm. The overheat alarm in my experience is often a "you screwed up and its too late alarm" You take a substantial risk after an overheat condition if you do nothing and keep running it unchecked. Aluminum engines do not take overheat well. Gaskets around the heads and water jackets can fail. The heads may also warp slightly. At the very least you should monitor the plugs after the next few trips for signs of water and steaming. (a very clean looking plug) Any missing or stalling at idle are clues that you need to pull the heads to replace gaskets before major damage occurs. To better protect the engine against overheat install a water pressure gauge on the engine. You will visually see that your water has stopped pumping as soon as it occurs and long before the engines alarm sounds. Mine has saved me a few times.
07-13-2009, 04:21 PM
Problem solved. As it turns out I had a bunch of kelp wrapped on my prop which caused the alarm to go off becasue the water intake was plugged. I removed the kelp at the dock and all seems to be fine. I drove the boat hard today and it responded perfectly so I think that this problem is behind me thankfully.
Thanks everyone for your advice.
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