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I got a boat last year with a 15hp Yamaha on it, the guy had just had a water pump impeller and carb kit put in it. It has always started first pull and given me NO problems. I have put about 6 hours on it since owning it.
The last time I took it out it, about 30 secs into the ride it sounded like I was throttling back on it, but it was still at WOT. RPM's slowly dropped over a period of 20secs until it just finally died, being held at WOT the whole time. I couldnt get it restarted so we used the ***** motor to get back. Here is what I have done/checked to try to figure this out:
Definitely getting spark, very bright blue.
Fuel system COMPLETELY replaced including tank, lines, primer bulb, fittings, fuel filter, fuel pump diaphrams.
Carb disassembled/cleaned, another carb kit installed.
Plugs checked, they looked good but put new ones in.
Reeds checked, worked fine but put new Boyesen Reeds in.
Compression checked, right at factory specs.
I thought I had found the problem with a cracked fitting that was allowing air to get into the fuel system, but that wasnt it. Grrrrr....
At this point Im guessing it has either jumped time/synchronization *or* there is some sort of exhaust restriction. It doesnt seem to be drawing any fuel into the cylinders, but I cant really tell. The spark is good but if it isnt firing at the right time, good spark wont help.
When you try to start it with the prop dunked in water, shouldnt bubbles come out the exhaust outlet? It also doesnt really help when you spray fuel in the carb(leaving choke open and throttle open so fuel get thru the carb), which leads me to think exhaust restriction/jumped timing.
At this point I think it would make GREAT target practice...
P.S. Thanks for the great parts service and prices, I've bought all the above mentioned parts from you guys!
The last time I took it out it, about 30 secs into the ride it sounded like I was throttling back on it, but it was still at WOT. RPM's slowly dropped over a period of 20secs until it just finally died, being held at WOT the whole time. I couldnt get it restarted so we used the ***** motor to get back. Here is what I have done/checked to try to figure this out:
Definitely getting spark, very bright blue.
Fuel system COMPLETELY replaced including tank, lines, primer bulb, fittings, fuel filter, fuel pump diaphrams.
Carb disassembled/cleaned, another carb kit installed.
Plugs checked, they looked good but put new ones in.
Reeds checked, worked fine but put new Boyesen Reeds in.
Compression checked, right at factory specs.
I thought I had found the problem with a cracked fitting that was allowing air to get into the fuel system, but that wasnt it. Grrrrr....
At this point Im guessing it has either jumped time/synchronization *or* there is some sort of exhaust restriction. It doesnt seem to be drawing any fuel into the cylinders, but I cant really tell. The spark is good but if it isnt firing at the right time, good spark wont help.
When you try to start it with the prop dunked in water, shouldnt bubbles come out the exhaust outlet? It also doesnt really help when you spray fuel in the carb(leaving choke open and throttle open so fuel get thru the carb), which leads me to think exhaust restriction/jumped timing.
At this point I think it would make GREAT target practice...
P.S. Thanks for the great parts service and prices, I've bought all the above mentioned parts from you guys!
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