Hmm. Craig's List Engine. ..The usual problem.

[kameika]

Hi. I just bought a 6HP, 2 stroke Yamaha for a dinghy. Mid 1990's vintage. Having played with outboards for years (Johnson 225HP's), I did the "garbage pail test" immediately.

The engine is in superb condition cosmetically.

The service manual is on order already. Could I pick your brains in the meantime?

No pee from the telltale. Hmm. ..After about 30-45 seconds. Not good.

Question#1 : How much time does the pump need to run before the telltale starts to pee?

Pulled the engine and performed a compression test. Both cylinders are within 5 pounds of each other. About 95 pounds.

Question #2: Seem about right??

Finally, I've never run an engine hot.. Any other things I should inspect to ensure there's not damage?

I should mention: This engine started easily and purred beautifully. These Yamaha engines are really nicely built...

Thank you.

Ken
Red Bank, NJ.



Anyhow. A new pump impeller is on order...

 

[steelespike]

Re: Hmm. Craig's List Engine. ..The usual problem.

Check the intake and telltale for mud dubber nests.
Did you fill the water up to the mountimg bracket for your test?
Speaking generically water should pee within 30 seconds.
CAREFULLY feel the head as it runs; should be to hot to hold your hand on but not so hot it burns.

 

[ugadawg187]

Re: Hmm. Craig's List Engine. ..The usual problem.

But it could take up to a minute before you see a pee stream tho right & that be ok? Any longer & you would have a prob with the cooling system?

 

[divinginn]

Re: Hmm. Craig's List Engine. ..The usual problem.

I would go ahead and replace the impeller,that way you know where you are starting from. They need replacing every few years anyhow. Good choice on the Yamaha,most bullet proof motor I have ever had.

 

[kameika]

Re: Hmm. Craig's List Engine. ..The usual problem.

Thank you, gents. I did touch the cylinder head -- hot, but not enough to burn. The paint is not blistered -- actually, the engine looks "like new". A small amount of "salty weep dust" on the gasket area between the head and upper section of the block. I've seen this before on other engines.

Is that normal for the Yamahas?

The head bolts were re-torqued to 8 ft-lbs. They had been loose. Following, re-checked compression. Again, 95psi +/- 3 psi both cylinders.

Seems right, no?

I agree with you: A new impeller is the right way to go.

Thank you again.

Ken
Red Bank, NJ

 

[kameika]

Re: Hmm. Craig's List Engine. ..The usual problem.

Everyone, as a reminder: The OB is a mid 1990's 6HP. --and trying to replace the water pump...

..But how to remove the lower unit??

I have disconnected the shift linkage. I removed FOUR bolts connecting the lower unit to the mid-section. I removed the Zinc aft of the lower unit (normally, would expect a trim tab there. It seems to be a zinc.)

The lower unit would not budge.

With service manual in-hand (though the manual covers many engine models), they indicate a FIFTH bolt under the trim tab. 'I'm not seeing this. Under the trim tab, these simply does not seem to be space for a fifth bolt.

Can anyone suggest anything? Is there a fifth bolt? Do I have a stuck shaft??

Anyone out there have any suggestions! --VERY much appreciate your input.

Ken
Red Bank, NJ

 

[kameika]

Re: Hmm. Craig's List Engine. ..The usual problem.

Okay. In the spirit of helping the poor soul for the future. All fixed. But this is interesting.

to start: No peeing. Seemed hot. I did not know the history on the 6HP 1992 Yamaha outboard.

To be safe, a water pump change. But.. The Lower unit would not come off. Four bolts for a 6/8 HP. Then a nice rap with a 5 pound soft hammer. Off the LU comes.

Next, off with the old water pump. This is where the story goes strange. See the first photo. This is the state of the old impeller. It's in pieces. Probably original to the engine. Damn.

Recheck compression. Both cylinders are at 95PSI. Good.

So. Where are all those little pieces? Time for a hunt.

Off with the cylinder head cover.. Lots of sand and little black pieces.

Next, time to blow out the tube. With the LU off and about 30PSI on a blow out tube (a little rubber tube to help) -- Blew out the water delivery tube. Also blew out the lower unit intake system.

Finally the pee hole. (tell tale.) That little bit of automotive vacuum line (black tube) to the compressor again -- and blew it out hard. 60PSI. Ouch

If you saw what came out of that, you'd abandon the tools. Sand, rubber, who knows what?


Finally, reassembled everything and re-torqued. Into the wheelbarrow (yes, a plastic garden wheelbarrow filled with water.)

Pee tube started okay. Then clogged again.

Out with the compressor and a little sharp screwdriver. Stop the engine, blow out the pee hole (forcing air all the way down to the propeller,) restart. Chop the debris at the pee hole and repeat.

Every two cycles, pull the engine cover ensure the engine is consistently cool.

After about 10 of these cycles, pee was VERY strong and consistent.

Ran the engine in the wheelbarrow for 30 more minutes. Perfect operation.

Yamaha may be the easiest engine to work on.

I hope this helps. Moral of the story? Change your impeller every two years. Buy a used engine? Tear it down immediately and change the impeller plus inspect.


Oh. IF you were wondering. The engine with a Zodiac were $750. New impeller was $20. The shop manual was $9.

I hope this helps someone.