HELP!!! Tohatsu 2cy 50hp

[Ralph11]

Hello, i am having a hell of a time with my Tohatsu getting it to run right. I have replaced nearly everything and it will not go over 3k rpm. Out of the water running on a garden hose it runs like a champ and sounds great. Drop it in the water and it goes less than 5mph and wont go over 3000 rpms… here is what i have done. NEW: Gas tank, fuel, fuel lines all the way back, new CDI, new stater, new plugs, new plug wires, new fuel pump gaskets and diaphragm, new head and exhaust gasket, compression is 125 on three cylinders, new carb kit, carbs clean about 8x, and cleaned ultrasonically, reeds are fine, new oil bottle and sensor, new fuel and oil filter and oil/fuel mixing t valve, all linkage on carbs in new condition, new shift cables, new remote. My boat has been at the mechanic in Lake Havasu for four months and he cant figure out why its not running properly… he said he has been in contact with Tohatsu and they are not giving him any useful information. He believes the engine is stuck in guardian mode but can figure out how to get it out of the that, maybe an electrical issue. Hope someone has some additional info that can help… thank you.. Ralph

[spartacus]

I wasn't even aware a Tohatsu 2-stroke had a limp-mode feature. That said, found a discussion on a Tohatsu 90hp and a water pressure sensor restricting it revving.

PM me and I'll send you the service manual. Pretty sure the water pressure sensor was for 2-stroke 80-140hp and an option for 60-70hp only.

It could be electrical. Any reason for swapping out the oil pump? Tohatsu wiring isn't tinned, so you can get oxidisation on wiring, so it could be a cut-off to the CDI, but simply due to lack of signal. Tell-tale green oxidisation on bullet connectors or the wiring turns black. You can test with a multi-meter for continuity.

Has the flywheel ever been off?

[Ralph11]

The limp mode was what the mechanic said tohatsu was telling him. They said in limp mode it would prevent it from going over 3000rpms and that’s what it’s doing. I’m not sure if there is a water pressure sensor on it. I did also replace the thermostat and gasket if that is the same.. yes, the flywheel was removed and replaced with a new one.

[neil.mccrirrick]

Can you rev it past 3k when not in gear?

[Ralph11]

Yes when hooked to hose in driveway it will rev up to 6000rpm. Once in the water and in gear 3000 tops. I have video of it running but not sure how to attach to this thread.

[smallribber]

Check the temp sensor connections

[Ralph11]

Not familiar where those are at. Can you advise? I’m sure my mechanic knows

[spartacus]

Originally Posted by Ralph11

Not familiar where those are at. Can you advise? I’m sure my mechanic knows

There’s usually a temperature sender on the cylinder head.

To be honest your mechanic should be picking up on this through a fault find. It’s one thing running it in a tank, but under load, then that’s the real issue.

[Ralph11]

I’ll check that out. This is an older outboard. Best guess is late 80’s early 90’s. Tohatsu can’t even tell me what year it is exactly because their system apparently changed,
so they say. So there is no computer hook up on it