Home service of Tohatsu 20hp

[Ducati]

Hello all,

I have a 20hp Tohatsu, the fuel injected one.

Had it from new, got the first 20 hour service done by the dealers and since then maybe use it about 10 times a year. Probably for 2 hours each time.

Got a quote for a service and it was £280, so I bought the service kit myself (£80) and just gave it a go.

I don’t really have any experience on outboards but do know a bit about motorbikes so I found it all quite straightforward.

Just one question though, when changing the impeller there is a mounting plate (to me feels like a aluminium gasket) and then a paper gasket too.

The old paper gasket didn’t come off in one bit, I had to try and scale it away with out damaging the metal surface underneath it.

I’m not confident I completely got it all off without putting the new one on, being paper or cardboard it was just to soft and falling apart upon touching it.

As this is far away from the engine what would happen if sea water passed gasket would it end up in the gearbox oil?

Hopefully I’m worrying about nothing.

Also worth noting the engine still looked brand new and both engine oil and gearbox oil looked really clear. A little carbon on the spark plus but other than that, great condition. So much so I probably shouldn’t had bothered with the service.

Thanks.

Dan.

[spartacus]

The metal plate is the water pump guide plate, normally stainless steel. The paper gasket (type of card) will usually tear on removal of the the water-pump housing at service stage. Best practice is to use a fresh razor blade and remove any trace of the old gasket. Try not to dig into the water pump plate when removing, and it will come off. You can even use fine steel wool to remove any residue.

The gasket ensures there's a clean sandwich of the two mating surfaces of the pump case assembly and guide plate. It won't allow water into the gearbox (that's the oil seal on the driveshaft) under pump case assembly, or clutch dog gear lever 'o' ring, or indeed the drain and fill screw seals. Other than that the only other thing that would allow water into the gear box is the prop shaft seal.

Don't skimp on service intervals would be my advice. Do it by the book and the engine will last a lifetime.

You can see the full parts diagrams here: https://tohatsu-partscatalog.aftama.com/us/search

[Ducati]

Appreciate your reply.
Many thanks.