Tohatsu M40C fuel delivery issue?????

[Dino Green]

I have a 40hp Tohatsu M40C, 361a, 88929 are the #'s I found on the motor. Seems to idle and start well. Little studder on idle but, at full throtle is seems to go pretty well and then starts to die. I notice that during idle the primer blub is pretty firm yet at full throtle when it starts to die it feels quite a bit softer and almost feels like it has air in the line, if I give the primer bulb a pump or two it picks right back up for a while then will start to die again until the pump is given to the bulb again. Could this be a clogged or dirty fuel pump or is it a possible fuel pickup issue.
Thanks in advance,
Dino

 

[John_S]

Re: Tohatsu M40C fuel delivery issue?????

I'd think that it would be more of a stuck/sticking check ball on the fuel hose side.

 

[Dino Green]

Re: Tohatsu M40C fuel delivery issue?????

Thanks Captain. Where is this check ball located? In the primer bulb? I was thinking of replacing all the lines, including the primer bulb, from the tank right up to the motor. The lines inside to cover all appear to be new. Would you suggest replacing the the connectors on the tank and on the line as it hits the motor also? They look ok.
Thanks again,
Dino

 

[John_S]

Re: Tohatsu M40C fuel delivery issue?????

I believe the Nissan/Tohatsu tank/hose has a check ball at the input connector, and one at the primer bulb, and possibly one at the outlet. I'd have to go back and check some docs to be sure.

 

[Sea Rider]

Re: Tohatsu M40C fuel delivery issue?????

Things to check: It could be dirt along tank pick up small filter, hose, primer bulb, gas lines, engine filter, gas pump. Begin with :

1-Unscrew interior fuel tank pick up filter off, remove existing gas, clean tank interior and filter as well, reassemble. Check removed gas for water intrussion, debris, gas station tank crap passed to you.

2-Connect connector to tank, remove engine connector, with point object push connector to open spring valve all the way down, squeeze primer bulb several times, check flow, if poor, obstructed line or primer bulb, if good volume, ok.

3-Place engine connector back on engine, release gas filter from mount, place a container under, squeeze primer bulb hard, if poor flow, small hose filter obstruction, if good, ok.

4-Gas pump, check diaphragms for wear or collapsed, clean, change, check back pump gasket for wear, clean engine body pump small suction hole, tight well all pump screws.

5-Quick disconnect fittings are very reliable. If still with problems, perform a good & complete carb clean.

Happy Boating

 

[pvanv]

Re: Tohatsu M40C fuel delivery issue?????

Everything Luis (Sea Rider) mentioned, plus, check for an air leak near the tank. Typically... a tank-end fuel restriction (such as the pickup filter) will cause a collapsed bulb (as long as the fuel pump is good). On the other hand, air leaking into the suction end of the primer hose will often cause a soft bulb, but not make it collapse.

 

[TOHATSU GURU]

Re: Tohatsu M40C fuel delivery issue?????

A brief word on the fuel pump itself. The diaphragms can have an actual perforation, but the most likely problem with them would be age related where they have become distorted. Due to the cost of the diaphragms and gaskets, if that is the problem, you should probably replace the entire fuel pump.