tohatsu 20hp problem

[cjb0909]

I have a new tohatsu 20hp motor on a 14' wide jonboat. I have been following the break in period correctly and can now hit full throttle. Motor runs great at idle and slow speeds but not at full throttle. will not push boat over 7mph. It sounds as if rpms increase just no increase in speed. Carb opens all the way at full throttle, any ideas on what i should check to save a trip to a dealer since there is not one close by. Thanks for any help.

 

[TOHATSU GURU]

Re: tohatsu 20hp problem

It's probably a spun hub in the propeller. You probably hit someting and tore it loose. The propeller is designed to catch at low speed so that you can limp in and replace the prop rather than be starnded out on the water.

 

[cjb0909]

Re: tohatsu 20hp problem

I checked the prop hub and it is fine. I looked at the spark plugs and the bottom one is wet and top one is dry, should it be? I also checked the gap on the spark plugs and it is .6 when it should be .9, could this be the problem?

 

[Sea Rider]

Re: tohatsu 20hp problem

I checked the prop hub and it is fine. I looked at the spark plugs and the bottom one is wet and top one is dry, should it be? I also checked the gap on the spark plugs and it is .6 when it should be .9, could this be the problem?

If you have finished the break in period, clean plugs and regap, tight them well with a socket wrench. What brand/type of plugs are you using, if NGK BR-7HS-10 in use, the correct gap is 0.9 to 1.0 mm. Try 1.0 tight gap.

Happy Boating

 

[TOHATSU GURU]

Re: tohatsu 20hp problem

If your RPM's increase and the boat go's no faster then you have a problem in the transmission of power from the engine to the propeller. The most likely case would be a spun propeller bushing. If you have eliminated that as the problem then you need to stop and take it into a dealer for warranty service as everything else will be difficult and expensive to repair.

 

[steelespike]

Re: tohatsu 20hp problem

Could just be a defective plug.Swap them see if the wet follows.
Otherwise I think its time for waranty service.