'85 Johnson 30hp wont start, please help!

[matt9923]

Re: '85 Johnson 30hp wont start, please help!

BTW, I am very untrusting of other folk's comrpession gauges. Do you have any other outboard you have access to that runs well that you could check and see what your gauge says? Those gauges have been known to be WAYYYY off. I've never seen a motor that had unstuck piston rings on it that had only 30 psi.
Good luck,
JBJ

Ya i agree only time i saw under 30psi their was a hole in the piston and a broken valve...
Matt

 

[Bradley_G]

Re: '85 Johnson 30hp wont start, please help!

I'll check and see if I can find another motor to test on. Also another motor to mount to my transom....lol.

 

[HybridMX6]

Re: '85 Johnson 30hp wont start, please help!

Even if it's a car it should at least help you see if your gauge is just reading way low. I know comp. gauges vary a lot. SOme read higher, some read lower. I have both a compression gauge and also a leakdown tester. Never used the latter, decided motor needed rebuild before I used it.

 

[rusirius]

Re: '85 Johnson 30hp wont start, please help!

so I changed the gaskets (cylinder head, water cover, bypass cover) and connected everything back up and the compression is only 60psi in each cylinder. It doubled teh compression that was there, but it still wont fire up. any suggestions? should I try the cover plate on the other side of the head? any tell tales that it is a gasket or something else?

I lightly sanded all surfaces and cleaned them using compressed air afterward, and when re-installing I used the proper sequence and I torqued all bolts to about 20lbs.

Any help would help.

I have pretty limited experience with OB's so take it for what it's worth... But if the motor overheated bad enough to melt the insulation off wiring then I'd think it almost certainly warped the head. Even with a new gasket a warped head is not going to give good compression.

If you can find a decent machine shop the could probably check the head for you (and as a plus dunk it and clean it up real good) for very little... They can also plane it if needed... Last time I had a auto head done it was like $30...

 

[Bradley_G]

Re: '85 Johnson 30hp wont start, please help!

Yeah, perhaps I can try that before spending 500 bucks on a new motor. Would I be able to tell with just a straight edge whether or not the head has been warped or will I need more precise instruments?

 

[HybridMX6]

Re: '85 Johnson 30hp wont start, please help!

I've heard of just laying the head on a piece of glass and looking at it from underneath. Never tried it myself, but it's a suggestion.

 

[wbeaton]

Re: '85 Johnson 30hp wont start, please help!

I've heard of just laying the head on a piece of glass and looking at it from underneath. Never tried it myself, but it's a suggestion.

As Brad said, you have to plane the head. I wasn't kidding when I mentioned it in an earlier post.

Place a piece of 400 grit wet/dry sand paper on a piece of glass or other truly flat surface. Place the head on top of the sand paper and sand it in a figure 8 pattern. Check the sanded surface often. The high areas will show signs of sanding whereas the low areas will not. Stop sanding once the entire surface shows the sanding marks. Your head is now planed. You should do this anytime you have the head off. Do not remove anymore metal than necessary.

The cylinder may be fine, but the rings may still be toast. Did you pull the covers and give them a good inspection as suggested? You need to press on them to make sure they are still springy. No spring = no compression.

 

[Bradley_G]

Re: '85 Johnson 30hp wont start, please help!

OK, so here's what I did today:

I took off the Head and Bypass cover again, checked the rings for spring, and it was there. I checked the head on a piece of glass and it seemed to be just fine, but I took ya'lls advise and sanded it a bit anyways. I actually took a sharpie and marked the entire surface so that I could verify that it was sanded. I put it back on an decided that instead of 20lbs of torque on the head bolts as one from this forum had reccomended I torqued them at 35, as well as the bolts from the bypass cover. I checked the compression after that and I had 90psi. Whoo hoo! improvement, it wasnt firing up still but it sounded as if it wanted to.

Long story short, I had a small leak in the fuel line at one of the connectors, and also my tube in the gas tank was sucking in some air and it wasnt getting the fuel it needed. After those adjustments, I get it to fire up, and with a little carb/throttle adjustments, I am back up and running like new.

Thanks a million for all of your help, you saved me much heartbreak of ruining my first outboard beyond repair. And now Because of this forum I have a wealth more knowledge of outboard engines.

and from now on the first thing i'll ever check when my motor starts is that pee tube.

 

[matt9923]

Re: '85 Johnson 30hp wont start, please help!

Nice. Did you get it back on the water? 90 seems low but i don't know what your motor is supposed to be. After it warms up check the compression again.
I constantly check my tel-tale and make sure its pumping.
Matt

 

[HybridMX6]

Re: '85 Johnson 30hp wont start, please help!

Nice. Did you get it back on the water? 90 seems low but i don't know what your motor is supposed to be. After it warms up check the compression again.
I constantly check my tel-tale and make sure its pumping.
Matt

Congrats on getting it back up and running, it always makes ya feel good knowing you got it done and saved who knows how much money over paying someone else to do it.

I also always check my pee hole. I fish shallow water and flats a lot in East Central Florida, so I've run through my share of sandbars, mud, weeds, etc. It doesn't take much to clog it up. If you run in shallow water like that, it's also a good idea to check the prop and propshaft out once a month or so for anything wrapped around it. Remove the prop and just do a quick visual check. A small piece of mono wrapped on there will destroy the seal, then let water in the LU. (I speak from experience on that, for both myself and a friend of mine).

 

[jbjennings]

Re: '85 Johnson 30hp wont start, please help!

Glad to hear you got that thing fixed!!! You definitely saved yourself loads of dough fixing it yourself. I'll bet you could have bought a good used motor for what they'd have charged you to fix it at a dealer.
I am a little worried about the torque on your head bolts----they may be awful hard to remove if you ever need to again.
Don't catch 'em all......
JBJ