1982 90HP Outboard compression numbers - Eh?

[chuckndiscs]

So my 82 90HP Johnson seems to have stutter issues from dead stop and at times dies going in to gear. Read that could be compression issues ( amongst other potentials...) so I borrowed a compression tester. The numbers are: Left - 58, 58. Right - 38, 0. OMG!!! What!? I'm not sure I am doing it right as those numbers are Terrible!!

Facts: It idles just fine! It does go and when it goes gets my boat (78 18 ft Starcraft SS aluminum) to 42mph.

Questions:

1. Am I compression testing correctly?

2. What gives with one cylinder at 0 and the rest awful and I can get boat to 42?

Sigh... B O A T 's

Chuck

 

[tx1961whaler]

Re: 1982 90HP Outboard compression numbers - Eh?

Borrow or buy another tester. Those numbers look too low for reality. The "0" is worrisome, however.......

 

[levi_tsk]

Re: 1982 90HP Outboard compression numbers - Eh?

make sure its tight in the hole -mines got and o ring on it see if your is missing it

 

[boobie]

Re: 1982 90HP Outboard compression numbers - Eh?

Another compression tester is required here. Then a cyl drop test.

 

[chuckndiscs]

Re: 1982 90HP Outboard compression numbers - Eh?

I'll get another compression tester, thought it was a bit wacky. I did not have the motor at WOT, would that make a difference?

Thinking, regardless, 0 is not good. If it really is 0 what are the thoughts on that...completely screwed (ie: rings and gaskets won't fix it)?

 

[levi_tsk]

Re: 1982 90HP Outboard compression numbers - Eh?

nope just make sure youve got the plugs out and your battery is fully charged

having zero on one cylinder usually indicates a bad head gasket but for now id go to harbor frieght tools and buy myself a new tester -they have em for 15 bux
and like others have said no sense borrowing worry ....

cylinder drop test:

1. Turn it off.
2. Remove ONE spark plug lead and ground it. <---Place bolt into it and allow it to touch the engine block.
3. Restart engine and see if the engine runs any different. If it does run differently, that cyl is most likely working properly and is not the problem.
4. Turn it off.
5. Replace the spark plug lead and remove a different one.
6. Follow the steps above until you isolate the cyl causing the problem.

 

[yoster]

Re: 1982 90HP Outboard compression numbers - Eh?

I wouldn't worry just yet. That motor isn't going to push you to 42mph on 3 cylinders, let alone with the other 3 being pretty shot. By how you describe the running characteristics, it sounds like everything is ship-shape. I suspect the test tool or how it's being tested as the culprit.

 

[boobie]

Re: 1982 90HP Outboard compression numbers - Eh?

I use a good insulated pliers for pulling plug wires when mtr running and see if the cyl drops or not.

 

[archcycle]

Re: 1982 90HP Outboard compression numbers - Eh?

I'll get another compression tester, thought it was a bit wacky. I did not have the motor at WOT, would that make a difference?

Are you saying you are performing the test with the motor running?

 

[chuckndiscs]

Re: 1982 90HP Outboard compression numbers - Eh?

Are you saying you are performing the test with the motor running?

Nope, just have warm up lever in high rev position, I think.

 

[chuckndiscs]

Re: 1982 90HP Outboard compression numbers - Eh?

I finally bought a compression tester, results as they were looking at the powerhead:

120 psi 32psi

120 psi 112psi

Looks like the top right cylinder is bad and the other three are good....

I took some pictures - OH MY GOD!






Looks like I have at least a bore and re-fit a piston on the bad cylinder.

Questions:

1. What do you think did the damage?

2. It looks like damage was/has been done a while ago...no "fresh" marks, does that mean the "whatever" identified in 1 above is now out of the cylinder?

3. Would takeing the power head off, having it bored .20 over and a new pistion put in then remounting the powerhead take care of the issues, likely? OR Do I need more done / looked at?


I can take the powerhead off, no problem but am not experienced enough to id the issues and make sure its good to go to put back together and run.... that is where you very helpful folks come in!

4. How much would I expect to pay for a powerhead drop off, bore done in one cylinder, and new pistion put in in MN, roughly?

5. The cover had the marks in the same location as the piston, do I need to replace that as well? (did take pics but same as piston in same spots.

THANKS MUCH YOU ALL!

Chuck

 

[levi_tsk]

Re: 1982 90HP Outboard compression numbers - Eh?

question #1 if i had to put a cause on it id say it either got WAY to hot or someone had a BAD case of detonation from the timing being too far advanced OR it was running lean and all could have been minor by themselves but combined may have made for a trifecta of the damage you see there - if it were me and i had it apart id cough up for a full rebuild kit ... youll have a brand new motor then

question#2 MAYBE however the other three may be on the way out seeing how much damage has been done - have all four pistons scored like that is REALLY bad and who knows? maybe itll go another 4000 hours and never give you a lick of trouble again .... but it may just as soon as you got it back together and running blow out in another hole and then youre back tearing into it again fixing another whole buying another gasket kit

question #3 once again MAYBE
part two we can help you identify any problem parts especially if you post pics as you have here

question #4 is i dont know about your neck of the woods but my machinist charges 20 bux per hole to do an overbore and hes top notch might be more there might be less no telling if i have the bore done after the block checks out he'll magnaflux it for free
as for reassembly with a service manual and about 8 hours of your time im pretty confident most anyone could put a two stroke together PROVIDED they were cleanly and followed the instructions to a tee



sit down before you read the price on the link but its an OEM BRP genuine full rebuild kit... i have a guy i get parts from in TN that might be able to beat this price but id have to call him to find out but im pretty sure this is pretty close to where youll be for doing the full power head
http://cgi.ebay.com/ebaymotors/John...5045366QQptZBoatQ5fPartsQ5fAccessoriesQ5fGear

question #5 if it were me id take the cylinder heads AND block magnafluxed after i tore it down and BEFORE bought a another thing for this engine

 

[levi_tsk]

Re: 1982 90HP Outboard compression numbers - Eh?

i just noticed that this is only the starboard cylinder bank do you have pics of the port bank too?- i was under the impression that each bank had a piston with this damage...

 

[chuckndiscs]

Re: 1982 90HP Outboard compression numbers - Eh?

i just noticed that this is only the starboard cylinder bank do you have pics of the port bank too?- i was under the impression that each bank had a piston with this damage...

I have not taken any yet, I can tomorrow...


Let me make the pics clearer with some description: The only physical damage seems to be the pitting or idents all over the top pistion and the cylinder cover (the dings, dents, matchup from piston to cover). There is NO dammage to the lower piston or clinder wall, just the upper. I dont think the dammage has been continuing because they are fresh (clean metal where the last dent or impact was made)...maybe no necessarily - thoughts?

They are both black but I was assuming that was from just use - is it?

THanks -

Chuck

 

[levi_tsk]

Re: 1982 90HP Outboard compression numbers - Eh?

yeah they are sposed to be black but pitting indicates overheating , detonation, or running lean looks like you caught it early though ... that piston may have split or cracked overtime you can try pulling the transfer ports and the exaust cover to look at the condition of the rings but only a full teardown will tell you what the end result is ... and it will also tell you where to go from here do the other two pistons look like the one on the bottom?? black but clean? if so you might just wanna rering and rehone those 3 and have the bad one overbored and a new piston and ring kit put it but if i had it apart id deffinitely replace ALL the rings at the very least... a good machine shop would probably glaze break the other three for around 50 bux and it would help bring the compression to more even between all four
youd want to do this because if you just do the one bad cylinder and dont touch the other three youll have about 150psi on the overbore and 132psi on the other 3 and even though its high it'd still be out of spec and could cause a failure

a ring set shouldnt be much more than 20 bux each hole and a piston should be about 40-50 youll want to bore it as little as possible as this will also help to keep the compression even i think the least youll be able to go is .020" over though

 

[levi_tsk]

Re: 1982 90HP Outboard compression numbers - Eh?

if you put all new rings in after glaze breaking the cylinders youd basically have a brand new engine id expect the compression to come up to 140-145 if you put new rings and gotthe ring gaps correct on the other three with the fourth coming up to 150ish

 

[emdsapmgr]

Re: 1982 90HP Outboard compression numbers - Eh?

The dents in the piston top will be similar to the dents on the head. The top piston ring on that upper cyl broke. Once it broke, it caught on one of the ports and broke into little pcs. As the engine was running, the small pcs got smashed between the head and the piston crown. That's one reason why there is low compression. Also, the seal ring on the head gasket may be damaged on that cyl. You need to determine just why you had that failure. Possible the piston got hot due to excess carbon accumlation around the rinsets. As was mentioned, pull the intake side covers off and look at the sides of the pistons through the intake ports. You will be able to see if there is any carbon around the rings. Also possible the carb has debris in some of the jets that feeds that cylinder. It may have been running lean on that cyl. The rubber water diverters in the powerhead look good- and in position-they probably did not contribute to your failure. Would be nice to diagnose/know the reason for the failure prior to overhauling the block.

 

[emoney]

Re: 1982 90HP Outboard compression numbers - Eh?

Not trying to hijack, and I think my question will help the OP. Does it look like there's an excessive amount of carbon build-up or is this about normal for these engines? If so, could that be the culprit in this failure? If nothing else, it's good to know if you pop your heads off and see this, what the next step is.

If you hit 42 before, you might want to install seatbelts when you get 'er rebuilt. Thanks for the pics as this repair will aid a lot of us.

 

[chuckndiscs]

Re: 1982 90HP Outboard compression numbers - Eh?

I may have found a deal here in MN:

1. Myself
1A. I remove powerhead from outboard
1B. I reinstall.
1C. I drop powerhead off at outboard shop -

2. Outboard shop
2A. rebuild powerhead for $1499.00 with all new pistons on new bores, new bearings seals and gaskets.
2B. Provide install kits that include new thermostats,carb kits,install gaskets and water pump impeller for reinstalling the block.
2C. They have it for 2 weeks.

Thoughts???

I think its a little high but not real sure. I do end up with a basically new motor and I have not done the impeller or rebuilt carbs this year or last.

THANKYOU!

Chuck

 

[emoney]

Re: 1982 90HP Outboard compression numbers - Eh?

Well, I know this much, you can't buy a new motor for that unless you want to drop down a few horsepower.....like, say, down to a 9.9, lol. There's a lot of time and energy that goes into that job and every market is different. Like you said, you'll basically end up with a new motor and you'll at least know it's history, etc. Plus, you'll have the pleasure of knowing that you need to go through a "break-in" period. Something cool about saying that.

Price folks within 100miles of your location and see if it's a "bad deal" or not. Local market's tend to set their own figures as to what's fair and what's not. Can you make part of the deal that this guy has to include pics of the entire process to give us something to look at? LOL.