Assistance in identifying Yamaha 50HP 2 stroke

[rayethan]

Hi. I'm trying to find another way to identify the Yamaha 2 stroke I have. I doesn't have a tag from the factory on it. It is a 50 hp, 3 cylinder with oil injection. My guess is it is from the early to mid 2000's. Any suggestions on what to look for so I can identify it? If you think a picture of it from me would be helpful, let me know.
Thanks,
Ethan

 

[boscoe99]

There should be an alternate tag on the block. Usually in the vicinity of the starter motor. With some numbers on it. What are those numbers.

Look at the CDI. What letters/numbers do you see?

Look at the carburetors. What letters/numbers do you see?

 

[QBhoy]

I’d be able to tell within a few years if you posted a picture. Big Yamaha 2 stroke fan ! Almost a geek.

 

[rayethan]

Hi. Here are some of the pictures of the engine. The CDI has 6H4-21 on it. On the side of the block, just above the oil injection tank there is what appears to be a freeze plug with the number 383458 stamped on it.

I wasn't able to see anything other than some writing about torque specs on the side of the block where the starter is. I didn't take off the air intake to get a better look at the carbs.

 

[boscoe99]

A 6H4-85540-21-00 CDI assembly was used on USA 50 HP two stroke models from 1984 thru 1988.

In 1989 the CDI used was a 6H5 prefix CDI assembly was used.

 

[rayethan]

Thanks. Now to see if I can find a service manual. Over the winter storage, I've got a leak somewhere in the oil injection system. I'm storing the engine in the down position and oil has dripped onto the floor. The tank isn't empty so I'm not sure where it is coming from.

 

[boscoe99]

The parts catalog may be a better help to you than the service manual.

 

[boscoe99]

 

[boscoe99]

 

[rayethan]

Thanks. My guess is that it must be one of the hoses. I wouldn't think it would be leaking from the pump since it isn't under pressure. I'll have to keep investigating.

 

[mphelle8vld]

I had the same issue with a 1988 50hp, Oil from the tank gravity feeds back through the oil pump and seeps out through its worn driveshaft/seal, and then down the leg and out the exhaust. Mine would lose about an ounce over the winter.

 

[boscoe99]

Thanks. My guess is that it must be one of the hoses. I wouldn't think it would be leaking from the pump since it isn't under pressure. I'll have to keep investigating.

The pump is under pressure. Head pressure. Pressure from gravity. Oil tank is above the pump.

 

[rayethan]

I had the same issue with a 1988 50hp, Oil from the tank gravity feeds back through the oil pump and seeps out through its worn driveshaft/seal, and then down the leg and out the exhaust. Mine would lose about an ounce over the winter.

That sounds exactly like what I've got going on. Mine is leaking into the case and down to where the hose for the cooling water exits the case. It seeps out around that opening in the case.

I guess I hadn't thought about gravity in terms of pressure on the system.

Thanks for the info!