What is this piece of my tohatsu 6hp?

[brownoarsman]

As I was winterizing my tohatsu 6 HP sailpro, I noticed that exhaust was coming out of the big black rubber circle plug on my driveshaft, especially when the throttle was turned up (engine in neutral). When I took the flash photo, it also appears gear oil is coming out as well (shaft coated in blue). Puzzling as when I put in fresh gear oil I followed the directions to let it come out of the top hole before screwing in the bolt, and this piece is well above the top hole for the gear oil.

I RTFM'd and this piece is not listed (it is the circle above the number 12 in the attached picture. 12, itself, is the top bolt for changing the gear oil.). Checking the exploded parts diagrams on boats.net, this piece is listed merely as a grommet.

Anyone know if exhaust/gear oil coming out of this grommet is normal course of business? Thanks!

[Crew of Turning]

We have the 2003 version of that engine with the Nissan label on it. Identical I think and no, that is not normal. You can down load the complete service guide online which breaks out each part and part number. Without experience I would think that you have a seal failure.

[newhaul]

The parts manual lists it as exhaust leg grommet .
It is well above the top oil seal for the gear case. All that should be behind that grommet is exhaust gasses if you are getting exhaust out there I wohld check the rest of the leg for possible blockages. It acts like a safety valve to allow exhaust to escape rather than build up pressure. When it leaks how far is the prop below the surface of the water? ( the ooze I would have to assume is particulate matter from the exhaust mixed and in suspension with the cooling water.

[nigel1]

The grommet allows access to the clamp which connects the upper gear shift rod to the lower gear shift rod. This clamp needs to be slackened if you wish to remove the lower gear unit, which you will need to do in order to inspect or replace the water pump impeller.

[brownoarsman]

Thank you for the replies. The prop is not down too far on the boat. The cavitation plate sits about two inches below the water, and when I noticed the exhaust leak the cavitation plate was barely in the water at all as I had the outboard on a stand and the bottom in a bucket. No visible ooze, just exhaust, and only significant when fully throttled.

As next steps, I will drain the lower unit gear oil, check for discoloration (if it's getting out what is getting in!) and measure quantity to see if there was significant leakage. If not, I would imagine the issue is the exhaust and potential blockages.

Thanks!

[newhaul]

Most likely an aged and hardend piece of rubber is the big problem . (The grommet is worn and no longer fits snug in the acess hole.

[dgz3]

I'm assuming that the motor is a two stroke. In which case, the oil you see oozing out is simply unburned two cycle oil from your exhaust. There's just no way for gear oil to get up there.
Sounds like you need a new grommet.
And you may be mixing a little too much oil in your gas.

[svJasmine]

that is a cap to allow you to unhook the shift lever and possibly the shaft extension if it is a super long shaft. Exhaust coming out is not an issue, as exhaust blows down that leg to be released underwater.

[Sailmonkey]

I've lost that cap for my 5hp. It's nothing other than a cap. Exhaust and water will come out of that hole, not possible to be gear oil. The hole is there, as others have said, to allow the shift and shaft extension to be unhooked

[brownoarsman]

Thanks for the additional replies! Good to know where the linkage is (under the grommet/cap!) as I am meaning to check the impeller as well this year

[brownoarsman]

Got around to changing the lower unit oil. It was clear, so thanks to all the posters guessing right regarding that grommet. Just a little exhaust blowout after all.

[Scot McPherson]

its really hard to put too much oil into 2 stroke mix, especially on these older units. Remember to follow the mixing directions in the engine manual, NOT the oil label. Even so, it won't hurt anything to double the amount of oil recommended. Many oils these days just flat out recommend 50:1 when some older engine want 25:1 or even more. The oil is there to lubricate your engine, and some extra coming out is not harmful to your engine in the least bit.


What IS harmful is to run the engine too lean. The engine isn't getting lubricated right if you mix 50:1 and the manual says 25:1.


A little Extra oil is ok and even good, too little even a little too little is very very bad for your engine.

[brownoarsman]

Whoops, forgot to mention. My tohatsu is a 4 stroke, but I will make sure to feed my lawn mower appropriately

[thomm225]

What year is you motor?

And is the discoloration around the rubber plug from the blow by?

I have basically the same engine, but it's a Mercury 5hp, 25 inch extra long shaft 4 stroke.

Mine's a 2011 and I have yet to see smoke or oil come from around that plug. I wonder if your screen is blocked.

You said you hadn't changed the impeller yet. How long has it been?

I've changed mine once almost 3 years ago now

Btw, my lower unit oil is never clear. I change it yearly

Here's the shop manual for the Mercury which is the same I believe. Section 8 is the lower unit.

http://boatinfo.no/lib/mercury/manuals/4-5-6.html#/192

[brownoarsman]

It's a 2015. I believe the discoloration is from the exhaust, but do not know. I initially thought it was from the lower unit as my lower unit gear oil is blue. However, that oil looked fine with no discoloration or floating bits. I haven't taken the lower unit off to inspect the impeller as it's a bit of a chore, but haven't noticed any diminished output stream or anything that would lead me to believe the impeller is damaged. Still intend to inspect the impeller, just need to elevate the motor to get at it. Like you, I have the 25" shaft which is a bit of a struggle!