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Hi everyone, I have been reading these threads for years and found them very useful, this is the first time I have needed to post as I have always found my answers in previous threads, unfortunately not this time.
I have a Yamaha 115 2006 2 stroke. I have been running it on the same custom built speed boat for 10 years. Had a problem with the gears recently so had them rebuilt, while it was apart I replaced the water impeller.
I am not sure if it was directly after this repair or shortly after my engine began to overheat. The 2000RPM limiter kicked in and it took me a while to figure out it was overheating as there was no audible alarm. Checked timing and fuel supply, cleaned carbs, filters and replaced fuel line but no luck. When I realised it was over heating I checked the tell-tale.
In neutral the tell tale acts normally, increase throttle and it shoots out a good solid stream, then I tested out on water. Same problem with overheating. Rebuilt the water pump again, checked the poppet valve and removed thermostats but no luck. I noticed that when running in gear the tell tale would start good but then drop pressure, still water coming out but a very low stream. As soon as I saw this I stopped the engine rather than letting it get hot and engaging the rev limiter.
Tested a few different conditions and found that if I was trimmed all the way down the pressure stayed good, if I trimmed up at all it would start good for about 30 seconds then drop. My boat handles terribly when trimmed all the way down and the steering gets really heavy, also I use the boat for wakeboarding and it puts out a better wave when trimmed up a little. So annoying that I can't use it at the correct trim. I noticed that it would almost always lose pressure when turning a corner but seemed ok when in reverse although I couldn't really open up the throttle in reverse to properly check.
Whenever water pressure dropped all I had to do was stop, rev the engine in neutral and it would go back to normal and I could start up again.
Seeing as nothing has changed in 10 years I can't understand why this is happening, the anti-cavitation plate is about level with the bottom of the boat and the water inlet seems to be fully submerged in the water. I even changed the strainer on the inlet to see if that helped.
I also cleaned the hull, which was pretty dirty of barnacles, weeds and algae. There are quite a few dings in the hull from chipped paint and epoxy, so maybe there is some turbulence created under the hull that is causing air bubbles to get into the inlet. But I have seen my hull in a lot worse states than it is currently and never had a problem like this.
Is there anything I am missing? Has anyone experienced anything like this before? Could I have made some elementary mistake when rebuilding the lower leg?
Thanks in advance
I have a Yamaha 115 2006 2 stroke. I have been running it on the same custom built speed boat for 10 years. Had a problem with the gears recently so had them rebuilt, while it was apart I replaced the water impeller.
I am not sure if it was directly after this repair or shortly after my engine began to overheat. The 2000RPM limiter kicked in and it took me a while to figure out it was overheating as there was no audible alarm. Checked timing and fuel supply, cleaned carbs, filters and replaced fuel line but no luck. When I realised it was over heating I checked the tell-tale.
In neutral the tell tale acts normally, increase throttle and it shoots out a good solid stream, then I tested out on water. Same problem with overheating. Rebuilt the water pump again, checked the poppet valve and removed thermostats but no luck. I noticed that when running in gear the tell tale would start good but then drop pressure, still water coming out but a very low stream. As soon as I saw this I stopped the engine rather than letting it get hot and engaging the rev limiter.
Tested a few different conditions and found that if I was trimmed all the way down the pressure stayed good, if I trimmed up at all it would start good for about 30 seconds then drop. My boat handles terribly when trimmed all the way down and the steering gets really heavy, also I use the boat for wakeboarding and it puts out a better wave when trimmed up a little. So annoying that I can't use it at the correct trim. I noticed that it would almost always lose pressure when turning a corner but seemed ok when in reverse although I couldn't really open up the throttle in reverse to properly check.
Whenever water pressure dropped all I had to do was stop, rev the engine in neutral and it would go back to normal and I could start up again.
Seeing as nothing has changed in 10 years I can't understand why this is happening, the anti-cavitation plate is about level with the bottom of the boat and the water inlet seems to be fully submerged in the water. I even changed the strainer on the inlet to see if that helped.
I also cleaned the hull, which was pretty dirty of barnacles, weeds and algae. There are quite a few dings in the hull from chipped paint and epoxy, so maybe there is some turbulence created under the hull that is causing air bubbles to get into the inlet. But I have seen my hull in a lot worse states than it is currently and never had a problem like this.
Is there anything I am missing? Has anyone experienced anything like this before? Could I have made some elementary mistake when rebuilding the lower leg?
Thanks in advance
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