70 horse cylinder scored

[scubaman67]

Johnson 1994 70 horse outboard, used in salt water. Compression in cylinder 1 and 3, normal 2 cylinder 75 lbs. removed head found Middle cylinder scored. My question is can this cylinder be sleeved, bored. Is replacing the entire powerhead to my advantage? approx cost and procedures for sleeving or boring.. I'm pretty mechanically inclined, but have not attempted any project this large before. I've searched through the forum archives and haven't found out how to do this..

 

[Walker]

Re: 70 horse cylinder scored

If you've still got 70# I'd guess it can be bored, maybe as little as .020, new piston and you should be set. The bore job should only be done by a machine shop that has experience boring outboard blocks. You need to determine what caused that cylinder to sieze and correct the problem or it will just happen again. <br />This will involve a complete teardown of the powerhead.

 

[scubaman67]

Re: 70 horse cylinder scored

Hmmm, I guess thats good news. Water in fuel tank, made it into motor, cylinder scored. My mechanic told me that the scoring happened over time, sounds like BS to me since motor ran terrible only after water was introduced. Complete teardown of powerhead scares the hell out of me, but reassembly sounds even worse. Any tips? Bangin my head against the wall ain't workin..

 

[2cycle]

Re: 70 horse cylinder scored

Scubaman<br /><br />A rebuild is not that bad if you take your time and have a manual (a must). I rebuilt a '76 70 HP with only basic mechanical experience on my part. You can get the ring squeezers at your local auto parts dealer. While you have the carburetors off, take them and have them cleaned/rebuilt or do it yourself. Like Walker said, talk to your local repair shop and ask them where they send their blocks for boring. And take the new piston with you when you drop it off.<br />It will be very satisfying when you finish.

 

[KYHunter2]

Re: 70 horse cylinder scored

Yep, If you take your time, and read the teardown, rebuild procedure a few times before you start.<br /><br /> And make sure to THOROUGHLY CLEAN everything before reassembly.<br /><br /> You should be good to go. <br /><br /> I've done a v-4 , just honing and changing 1 piston.<br /><br /> I've also done complete rebuilds.<br /><br /> If it were mine, being its relatively new. <br /><br /> I would have all three holes bored the same and replace all the bearings. And con-rod bolts.<br /><br /> The extra pistons won't cost that much . And probably about another hundred, or so ,to bore the other two cylinders.<br /><br /><br /> You can get complete rebuild kits. Both OEM, and aftermarket. <br /><br /> <br /> Usually cheaper then buying individual parts.<br /> <br /><br /> You can probably use the old bearings again . I'd be sure to replace, the con-rod bearings . ( crank and piston pin end ) <br /><br /> You'll definately want to rebuild carbs. ( easy )<br /><br /> If you do this , you'll have essentially a new motor. <br /><br /> Whatever you do , when you get this motor going, or get another one. <br /><br /> You need to install a water seperator fuel filter. <br /><br /> It will give peace of mind, and prevent this from happening again.<br /><br /> Good-Luck,<br /><br /> KYHunter

 

[scubaman67]

Re: 70 horse cylinder scored

Thanks for the help guys, I'll let you know how the rebuild goes.. won't be attempting it too soon though, just bought a bigger boat with bigger problems.. You'll probably be reading a few posts concerning that boat here shortly.. thanks again...

 

[Dhadley]

Re: 70 horse cylinder scored

If there was water in the tank it will get into all 3, not just one cylinder. If there was water only in the middle cylinder it didn't come in with the fuel. <br /><br />Water in all 3 means he made a good guess. Water only in number 2 means he's guessing.<br /><br />Let's look at this - the top rpm when it ran good was about 5500 or so. And you never run it hard, mostly cruise around about 3000-4000 rpm. Right??<br /><br />Was the fuel fresh (less than 45 days old) and 87 octane?<br /><br />Champion plugs?<br /><br />Carbs clean?