Tohatsu 9.8 oil light

2012 model 9.8 Oil light comes on when I give the motor the trottle. It runs fine at idle. It's runs ok at a slow speed but nothing over half throttle. I've had it to the dealer twice and both times they replaced the oil sensor and it would run the next day ok and after that the light comes on at high speed and I have to back off the trottle and limp back to the dock. I have had it in the shop and watched them run it in the tank and no light but once under a load the light comes on. It's mounted a 14 foot run about so not much weight is being pushed.

The oil checks out fine on the dip stick not over full. Using recomended brand and weight of oil. The shop did a oil pressure check and it was at the recomened pressure, along with a temperature check of the engine while running in the tank.

The motor has been in the shop almost as much as it has been out of the shop. 3 months the first time and 5 months the second. I purchased the motor from the shop where it is getting serviced. Any help would be appreciated thanks.

Hmmm, a weird set of symptoms. Normally you will get an oil light at idle and then have it go off when you give it throttle. It's also quite a new motor which is strange. If it was older I would suspect that all your clearances have opened up meaning that even if the pump was pushing the correct volume of oil the increases gaps would stop it ever getting up to the required pressure. So they are replacing the sensor, but what about the leads heading into the CDI? Could they be damaged leading to high resistance? You haven't mentioned the oil filter but I'm presuming that was checked/ replaced too. Any chance of doing the oil pressure test while running the boat under load?

Stuart

No the motor wasn't pressure tested under load for the oil pressure. The 9.8 doesn't have a filter just a screen.

Put a gauge on it and run at speed. If the pressure is OK, you have a fault in the electrical system.

Thank you Paul. We ran the motor in the tank for about an hour wide open and the pressure was fine and no oil light came on but when it was on the boat under load oil light came on.

Run it on the boat with a gauge. If the pressure is good, and yet you get a light, there is an electrical problem -- sender, LED, CD, or wiring.

Thank you Paul