1998 Tohatsu 9.8 runs poor under load

[Chesapeakegem]

Can anyone offer me some advice on this problem?
Have this 9.8hp Tohatsu 2 stroke which runs like a champ all through the throttle range when its on a test stand being cooled via the garden hose with water cuffs. But once it's mounted on the boat and under load she runs very poorly at anything above 1/4 throttle.

I had a local shop just complete a fuel system and carb service as it would run great and then just quit running before. Now it won't quit but runs like crap...

The plugs are new and according to manufacturer's spec, properly gapped, .9-1.0mm. Engine starts right up usually on first pull with 0-partial choke. Been running 92 octane premium since I have a 6 gallon tank and only use the motor for getting a 27 foot sailboat in and out of it's slip. I typically wont burn more than 1 or 2 gallon's a month so the mechanic recomended using premium.

The cooling water coming out of the tell tale is more of a spray than a stream, it is hot but not too hot to maintain skin contact. I can touch the top and the sides of the cylinders while running without loosing skin. There is good cooling flow out the prop hub. I am not the original owner of the engine and don't know it's service history I'm thinking its time to install a new water impellor.

The engine does have a remote start and throttle assembly which it runs from when on the boat and is not hooked up when the engine is on the test stand. Other than the remote throttle, key start and 6000lb sailboat I can't understand why its runs so poorly/differently.

I'm hoping to get some advice which may be something I can do myself. If I need to take it back to a service mechanic then so be it...

Thanks, Mike

 

[pvanv]

Re: 1998 Tohatsu 9.8 runs poor under load

You need a good diagnosis. The year is unimportant, but precise model/serial is critical. You probably have a 9.8A3. Could be anything, but still sounds like a carb issue. Was it properly submerged in dip and then reassembled?

 

[Chesapeakegem]

Re: 1998 Tohatsu 9.8 runs poor under load

Thank you for the reply Paul. I'll take it back over to the service mechanic that did the carb service. I was hoping it might be something that I could do myself and not have to wait 2 weeks for the service work to be completed. I'll let you know what we find.

Thanks again!