Yamaha 4hp runs wild

L

Laksfisker

Recruit
Joined
Aug 28, 2007
Messages
2
I have a 4hp yamaha outboard motor that seems to run ok but when the throttle goes over the start mark the engine starts to go faster and faster until I throttle off. When this happens the boat actually seems to slow down. Have just changed the oil and removed some fishing line from the propeller but it didn't fix the problem. Any ideas?
 
B

BruceAML

Petty Officer 1st Class
Joined
Feb 26, 2007
Messages
371
Re: Yamaha 4hp runs wild

What is the year and model of your engine? Am I correct in thinking that you are using the original fuel tank that is under the cowling? When you turn the handle back to idle does the engine respond?
 
L

Laksfisker

Recruit
Joined
Aug 28, 2007
Messages
2
Re: Yamaha 4hp runs wild

Hi;
I think it dates from 1998, I'll pop down to the seafront later to read the model number. When I return the throttle to idle the engine speed drops. The motor works perfectly as long as I don't put the throttle over the "start mark".:confused:
I'm using a separate fuel tank The one under the cowling doesn't work since the fuel lines are blocked (with rust I think).
 
J

jl_photo

Petty Officer 2nd Class
Joined
Jul 30, 2007
Messages
108
Re: Yamaha 4hp runs wild

with the cowling off and the throttle at idle move the linkage on the carb by hand and see if it works predictably. if this works you might have a linkage problem. if it doesn't you may be sucking some air through the on-board fuel tank. make sure the selector valve is in the right position.
 
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