Nissan 18 2-Stroke Watered down oil around prop

[jonaddis84]

I just got a great deal on this '99 18hp with maybe 4hrs from an old Nissan dealer.

Motor runs great, but since its sat for 10 years I decided to replace the impeller to be safe. Turned out it was perfectly fine though so now I have a spare.

While I had the lower unit (LU) off I noticed a BUNCH of nasty watered down oil almost completely blocking off the exhaust port in the LU. There was also some of it in the top side just above the LU. I sprayed some degreaser and washed it out of there.

After re-assembling, I ran it for a few minutes with the muffs to make sure everything was cool. Now after sitting in the shop overnight I noticed some more of that nasty oil has dripped onto my floor.

What causes this?

It cant be LU gear oil, Ive replaced that twice, once right when I got the motor a few days ago, and I drained it before doing the water pump. There was still a full amount of gear oil that drained out of there.

Could it be running too rich or I have too high a oil ratio in my gas and its spitting it all out the exhaust?

Thanks

 

[pvanv]

Re: Nissan 18 2-Stroke Watered down oil around prop

The 10-y-o impeller should not be trusted, as it has undoubtedly dried out a bit. Even in fresh water, no silt, and light use, we figure 3 years max on those rubber bits.

The crud in your exhaust housing and area is likely unburned oil/fuel mix. It's probably in everything, including the combustion chambers. Get a can of Tohatsu "Engine Tuner" from your dealer, and follow the instructions. Use the whole can, just like it says on the label. It will smoke like crazy. That will probably do it for you. Plan on changing the plugs afterward.

FWIW, I question the 4 hour claim on the motor, since that much accumulation is unlikely if run for only 4 hours at 50:1 oil mix and proper air/fuel mix.

BTW, always include the entire model (in the format M18E2) so we know what motor you have.

 

[jonaddis84]

Re: Nissan 18 2-Stroke Watered down oil around prop

Hey thanks for the reply.

I didnt clarify, I didnt leave the original impeller on, I replaced it with a factory tohatsu part, but since the original looked completely fine to me Ill keep it on hand in the boat just incase I need an emergency replacement.

Im going to get myself a can of that engine tuner as soon as I find a dealer close by. Is there another brand that works as well, perhaps a mercury product?

I definitely questioned the 4hrs he told me also. But looking inside the motor cover Id have a hard time believing it has much if any more than that on it. We also have a newer Johnson 50 with maybe 10hrs on it and its a heck of a lot dirtier inside than this Nissan.

The day before I did the water pump we trolled with the boat for a good 3hrs straight, and I think my fuel mix may be off since I just went from a 32:1 mixture engine to this 50:1 and just guestimated adding gas to lean it up. Maybe that caused the excessive gunk in the exhaust port?