Tohatsu 90HPa slows then dies at full throttle

[hollyasc]

We just purchased a 1995 boat/motor. The seller said he only used a to troll a few times, but ran great. We get it out on the water and start having problems right away. It idles fine, and will run fine at low RPM's. When trying to go at higher RPM's it will begin to loose RPM's and then will die. Took it to an authorized dealer 3 hrs away and he cleaned carbs and said he couldn't find any other issue. We brought it home, took it out on the lake and had the same issue. We have since changed the fuel line, checked the fuel filter, and we have drained the fuel tank, thinking the fuel might be old. Does this sound like we need a new fuel pump, or does anyone have any other suggestions before we take it back out on the water?

 

[pvanv]

Re: Tohatsu 90HPa slows then dies at full throttle

This could be anything, but...

It sounds like you are running out of gas. At least to the cylinders. Could be either a lack of fuel availability, or an air leak allowing air to come in instead of fuel.

A full diagnosis should determine whether there is adequate fuel being supplied to the carbs or not. If not, could be either a pump issue, a restriction, or a seemingly minor air/vacuum leak in the fuel line.

 

[hollyasc]

Re: Tohatsu 90HPa slows then dies at full throttle

Thanks Paul. We took the boat out again last night. It ran for a while then it slowed and died again. We check the ball and it was completely sucked flat. So I guess we figured we have an occlusion from the fuel tank to the ball. Thanks for your help.

 

[Blk-n-Blu]

Re: Tohatsu 90HPa slows then dies at full throttle

Sounds like the tank is not venting, You are opening the vent before starting up.

 

[hollyasc]

Re: Tohatsu 90HPa slows then dies at full throttle

The tank is in the floor with a permanent vent. The vent is not clogged. We think it is in the valve that connects the tank to the fuel line. Working on replacing that.