Do I need a new head?

[gatormc]

Ok, to start with, I have a 1993 Johnson 15hp outboard, model number J15RETB. In August while cruising down the St. John's the motor started losing power, and then quit. It sat for a while (I was moving and we had 2 Hurricanes hit us almost directly), and when I started troubleshooting I found that I had spark on only one plug. Figured out the coil was bad (bubbled up, looked charred, ohm meter showed different reading for the coils). Replaced it and the spark was fine, but the motor no go! So we cleaned out the carb, and nothing doing. So I checked the compression and found 0 psi in the top cyl, and 30 psi in the bottom. Put some oil in the top cyl, and it would push about 24 psi but it would quickly dissapate. So, after speaking with some friends, and reading this board, I decided to pull the head. This is what I found...<br /><br />

<br /><br />

<br /><br />The picture above shows a nice chunk out of the top cyl. head.<br /><br />

<br /><br />And the corresponding section of the head gasket. <br /> <br />

<br /><br />The pistons look pretty good, and the top cyl. wall looks fine.<br />

<br /><br />But the bottom cyl. wall looks like it has two scratches (fairly deep) at the top. You can sort of make them out at the top of this picture. I will try to get a better shot shortly.<br /><br />My questions are as follows...<br /><br />1) Do you think I can fix the head, or should it be replaced.<br /><br />2) If I need to replace it, where can I find one, should I go with new or used (I would like to keep it cheap).<br /><br />3) Am I going to need to bore the cyl. or just hone it. (I will provide better pics).<br /><br />Any help is much appreciated.

 

[Silvertip]

Re: Do I need a new head?

The head is "toast". The chunk that was taken out of the head is on the sealing surface so a new gasket would not seal. It is also obvious the engine was injesting water as that cylinder is virtually spotless compared to the other one. Not that it matters, but are the score marks in the cylinder in line with the piece that came out of the head? I suspect the cylinder would need boring to make this a worth while repair. The head should be available used from any local outboard salvage outlet. Or try www.twincityoutboard.com.

 

[rodbolt]

Re: Do I need a new head?

hello<br />if they are deep enough to hone they need boring. you may get by with surfacing the head and replacing the gasket for a bit. after its allassembled take it to a dealer for a leak down test. anything more than 15% is a rebuild reason. I draw the line at 12% but industry standard is about 15%.if it passes a cyl leak down test it will go a bit. optimal leakage is 5% or less.

 

[gatormc]

Re: Do I need a new head?

That is what I figured, a used head shouldn't cost more than $50-$75 I expect. Here are some better pictures of the scratches, but still not that great. I will probably call around tomorrow to find someone who will bore the cyl. I might as well replace some other things while I am in there, any suggestions?<br /><br />

<br /><br />The scratches are in the bottom cyl. the head is broken on the top cyl. so it isn't inline with the scratches.<br /><br />

<br /><br />I also found this little sliver of thin metal in the intake.<br />

<br /><br />Thanks for the quick replies. I will post updates and pictures as I progress. It should be a fun project at least.

 

[rodbolt]

Re: Do I need a new head?

you can take .015" to.020" off the head with no worries. if it cleans uprun it if it does not scrapit. just looking at the pics its time for boring and new pistons. on the 9.9 its esiest tohave the pistons changed on the rod at a dealer. I have done it with and without the tools called for in the book. with is definately the way to go. the pins are a light press fit and require the pistons to be heated before pin installation. but the rest of the tear down and reassembly is mostly easy. sometimes getting the two water tubes to go down the holes on reassembly is tricky but nothing a rubber band cant handle. you may wish to get with Dhadley or another tech in your area for advice on what machine shop to use. most auto machine shops cant get it right.

 

[gatormc]

Re: Do I need a new head?

Thanks again. I bought a used head for $50, and today I am going to by a flywheel puller so I can take the motor apart. I have read a lot about pulling the flywheel, but what about getting it back on. Do I just need a rubber mallet, or will it be more difficult?

 

[reeldutch]

Re: Do I need a new head?

you will need a good torque wrench and a flywheel holding tool

 

[gatormc]

Re: Do I need a new head?

Well, I took the motor in to the repair shop today, just so they could look at the damage. They basically said that because the sleeve seperated from the block (4th picture, bottom left side of the top cylinder) that I would need a whole new block (or a used one). What do you guys think, is this motor worth it, or should I just sell the good parts on Ebay or the classifieds. How much should I expect to pay for a used block. Again, it's a 1993 15HP Johnson. I would like to get on the water sometime this summer...I love shooting Sporting Clays, but it is hard to beat a day on the Stick Marsh! I will get a closer picture of the sleeve and post it soon.

 

[rodbolt]

Re: Do I need a new head?

resleeve it unless the casting is cracked. may be cheaper to find a used block or a reman powerhead