Tohatsu 18hp will not run at full speed / throttle

[marinodman]

Hello,
I have an 18hp Tohatsu outboard - 1990ish. When on the water it will not run at full speed/throttle. Carburetor has been cleaned and spark plug replaced. The motor starts strong on one pull and idles great. But it will not "open up" or go to full throttle/speed though. Doesn't stall, spit or sputter, just will not go full speed. Any ideas or suggestions as to what I should be taking a look at to resolve this?

 

[Jon Boat Jim]

Re: Tohatsu 18hp will not run at full speed / throttle

Sounds like a clogged high speed jet in the carb to me. You might try a Seafoam treatment (spray half a can of the aerosol spray through the carb throat while it is running and then put a can of the liquid stuff in 1 gal of gas + oil and run it out on the lake at WOT. If that doesn't do the job....clean and rebuild the carb.

 

[pvanv]

Re: Tohatsu 18hp will not run at full speed / throttle

By all means, diagnose the problem. Whip out your trusty Factory service manual and check out the fuel, electrical, and mechanical systems, in that order. You could have something as simple as a vacuum leak in a fuel line, or as rare as a weak coil. For that matter, if your water pump is weak, you could be running a little too hot. BTW, spraying ANYTHING through the carb throat WILL NOT do ANYTHING for a dirty jet, and could possibly do damage. The jets are in the fuel passages of the carb, not the air (throat) passage.

 

[Sea Rider]

Re: Tohatsu 18hp will not run at full speed / throttle

Welcome to the forums.

How about a spun prop ? 13 years is a lot of time, probably rubber in hub is dried/worn out and prop is slipping when giving more juice, check...

Happy Boating