15 hp powerhead

[wdbill]

I just got a 15 hp Johnson motor off of craigslist and I thought the guy was honest but I didn't know what to look for and I got ripped off for $650. I took the motor out to the lake and it had know power at all after I got it started. It was a short trip. took the motor to a shop and he looked at it and seen the lower piston just had lots of play in the cylinder. he told me he will try to find a new powerhead for that motor. the motor is a 1986. I would take him to court but the bill of sale has AS IS on it. how much should I sink in to a 24 year old motor. the mechanic said maybe $500 more. do you think I should go to bass pro and get a new motor with a 3 year warranty and electric start for $2655 + tax this is a better price than cabelas $2809 + tax I didn't want to spend 2K + on a motor

 

[Haffiman]

Re: 15 hp powerhead

If only a sloppy piston, change it.
However if you depends on a workshop to do all your maintenance and repairs, get a new motor.

 

[bktheking]

Re: 15 hp powerhead

Take a chance

http://cgi.ebay.com/ebaymotors/John...0288912QQptZBoatQ5fPartsQ5fAccessoriesQ5fGear

 

[scanman]

Re: 15 hp powerhead

I agree with Haffiman, If you aren't doin the work youself It'll get way too expensive, way too fast! Hate to hear you got took that way! buyer beware!

 

[bktheking]

Re: 15 hp powerhead

Sloppy piston=worn cylinder, chances are "changing it" will lead to the same result.

 

[Haffiman]

Re: 15 hp powerhead

Sloppy piston=worn cylinder, chances are "changing it" will lead to the same result.

Those engines eats pistons!
Never had problems with the cylinders, but a lot of rattling pistons and failed wrist pins and bearings.
The 9.9 versions not much problems, but the 15 if run at the 'recommended' rpm, are quite short lived.
(they normally never do as people do not have tachs on those small ones!)
Not much more job to change the pistons than the power head, and parts costs a fraction.
Do-it-yourself, and it pays, but leave it to a workshop is another question.

 

[wdbill]

Re: 15 hp powerhead

what is difficulty to rebuild the powerhead with not ever working on a outboard motor before? do I need to have it machined? the cylinder doesn't seem to have any wear it seem to be smooth I found a rebuild kit on ebay.


http://cgi.ebay.com/ebaymotors/POWE...0852772QQptZBoatQ5fPartsQ5fAccessoriesQ5fGear

 

[Rick.]

Re: 15 hp powerhead

For your own sake I would do a compression test before I went any further. Bad spark could be the reason for poor power. Best of luck. Rick.

 

[scanman]

Re: 15 hp powerhead

Rick is right. If you run it & don't hear any knockin noise it could be anything. I bought that exact same kit for my 9.9. It's everything they promise. Highly reccomend 'em! If you have the tools & training to do the job, thats the way to go! Also plan on another $25-50 for the correct chemicals & materials to do the job. You'll need a sheet of glass, lapping compound, needle bearing grease, gel seal etc... I will warn you about the connectin rod realignment. It took me 4 days of cursin it, a day to take it to the local shop, where they refused to do it or (I wouldn't want to pay the bill) & three more days of cursin to get it right!. It gets very technical, so if you don't have the skills & tools already, you could wind up with a pile of useless parts. I will give you all the advice I can & I have quite a few pics but if your not a mechanic, or raised by one (like me) you might reconsider. $650 for the motor & $250 for the kit = $900. Look at what they sell for & think twice. Again sorry you got took, but if there's any help to be had, it's Iboats & bktheking. We'll all help if you decide to do it yourself!
P.S. You won't know if it needs machining until you tear it down & take measurements.

 

[bktheking]

Re: 15 hp powerhead

And Rick, The Machinist, F_R, Jmendoza, 1946Zephyr, Ezeke, Faztbullet, etc etc etc. We've all had our hands in one motor or another, a 2 stroke is a 2 stroke and we can all lend you advice during the rebuild. You will also need torque wrenches or borrow them and a cylinder hone.

 

[scanman]

Re: 15 hp powerhead

Those engines eats pistons!
Never had problems with the cylinders, but a lot of rattling pistons and failed wrist pins and bearings.
The 9.9 versions not much problems, but the 15 if run at the 'recommended' rpm, are quite short lived.
(they normally never do as people do not have tachs on those small ones!)
Not much more job to change the pistons than the power head, and parts costs a fraction.
Do-it-yourself, and it pays, but leave it to a workshop is another question.

I agree to a certain extent. low or poor quality oil has led to many bearing & pin failures. However, as I've done with my 9.9 (with the help of many iboats experts) You should probably plan on all new parts while you have it torn down. Why would you put in one new piston & rings & not do the other? Just enjoy tearin it down, or what? If you go into it, DO IT ALL!!! Otherwise you'll be back in it soon. My motor ran without trouble for 35 years. When I tore it down I did it right so that the boy will get 35 more. If you skimp on it you'll wind up doin it again!

 

[samo_ott]

Re: 15 hp powerhead

I would do a compression test before going any further. Maybe the shop was wrong. How did they test it?

And was this an OMC shop or a generic place?

 

[ChrisAG]

Re: 15 hp powerhead

The 9.9 versions not much problems, but the 15 if run at the 'recommended' rpm, are quite short lived.

Ineresting... was this only for the years they recommended 100:1 oil, or are all 15's short lived if you usually run it at full throttle?

Mine is a 1978 15hp that I (as a kid) ran at full speed almost 100% of the time for 4 seasons, then put it into long-term storage until last year. It runs perfectly, but should I be taking it easy, say running at no more than 4/5 throttle?

 

[wdbill]

Re: 15 hp powerhead

He pulled off the head and the lower piston had all kinds of play and there was marks on the inside of the head where it was hitting and some lose metal.
but 1st he turned the flywheel feeling for presure then he removed the plugs and put his finger over the plug hole upper cylinder and it had presure lower had none.

 

[scanman]

Re: 15 hp powerhead

You need to find out where that loose metal came from to know the total extent of the damage. But like I said, If your payin the local dealer to work on it, stop now. If not, you've not much to lose.

 

[Haffiman]

Re: 15 hp powerhead

Ineresting... was this only for the years they recommended 100:1 oil, or are all 15's short lived if you usually run it at full throttle?

Mine is a 1978 15hp that I (as a kid) ran at full speed almost 100% of the time for 4 seasons, then put it into long-term storage until last year. It runs perfectly, but should I be taking it easy, say running at no more than 4/5 throttle?

The old 15 was rated far above 6000 rpm in order to get the 15HP out of it.
If you look at the props available, the only SST for high-speed is the one with the lowest pitch (except for the High Thrust).
Most users never changed the prop, but used the std delivered with the engine. That normally kept the rpm down even if the never got the 15 Hp out of them.
Those 'unlucky' ones that went for the high speed, got into troubles. Killed by the rpm as they never managed to get proper lubrication of the wrist pins/bearings.

 

[scanman]

Re: 15 hp powerhead

I'm not a prop expert, but I've seen lots of these motors outlast thier owners with proper fuel/oil mix reguardless of load charicteristics.

 

[wdbill]

Re: 15 hp powerhead

It is not a shop I took it to it is a guy that has been working on boats and motors for 40 years he got a nice shop in his back yard. He told me he is going to try to locate a good powerhead. but do I realy want to sink any more money into this piece of whatever! I think I may just go out and get a new one so that I can enjoy my self out at the lake. with a push of a button to start. but it is something for me to think about.

 

[ChrisAG]

Re: 15 hp powerhead

The old 15 was rated far above 6000 rpm in order to get the 15HP out of it.
If you look at the props available, the only SST for high-speed is the one with the lowest pitch (except for the High Thrust).
Most users never changed the prop, but used the std delivered with the engine. That normally kept the rpm down even if the never got the 15 Hp out of them.
Those 'unlucky' ones that went for the high speed, got into troubles. Killed by the rpm as they never managed to get proper lubrication of the wrist pins/bearings.

But then OMC apparently increased the power in 1981+ with a tuned exhaust, and the maximum rpm range went up from 5500-6500 (pre 1981) to 6000-7000. Did they do anything in this period to improve lubrication?

 

[Haffiman]

Re: 15 hp powerhead

To my knowledge, nothing.
The RPM increase not only resulted in shorter piston life time, but the impeller, particularly in salt water went into a yearly service item, at its best!