Johnson 50 very low compression on lower cyl.

[nautme]

Hi folks,
I'm new to boating, more or less, but stumbled on to your site. Last week I bought a used 20' Lowe pontoon with a 50 hp Johnson on it. The guy I bought it from hooked up some muffs and it started and Idled good, so I paid him. When I took it to the lake, as soon as I put it in gear, it would die. I have had some dealings with auto and motorcycle engines, so I pulled it back home and did some tests on it. Compression on the top cyl. was 130 and the bottom was 15. I checked the spark, and the top would jump about a 1/4" and the bottom about 1/2" on an ignition spark tester. Is there anything besides a blown head gasket or busted piston that would cause this in a marine engine? A friend suggested a decarb, but from my dealings with 2 stroke bike engines, that would seem to be a pretty good stretch. I don't know the year of the motor, but the model # is 50ESL73R and the ser.# is E3827589. The boat is a '93 Lowe. I suspect the motor is a little older than the boat.

 

[iwombat]

Re: Johnson 50 very low compression on lower cyl.

You might have a bad case of stuck rings. Although, that's some pretty low compression. Still worth a shot. Seafoam, PB blaster, MMO, or choose your favorite penetrating oil and load up that cylinder when the piston is at TDC. Wait a day or two and see if you get any improvement. If not you'll need to pull the head and maybe the side plate and inspect.

My guess is that lower hole is toast.

 

[samo_ott]

Re: Johnson 50 very low compression on lower cyl.

I know it's a tad late now but when I got to buy a motor of any value I always take a compression gauge with me and tools. It's quick and easy to check an engine.

 

[tashasdaddy]

Re: Johnson 50 very low compression on lower cyl.

the motor is 20 years older than the boat. good dependable motor when properly maintained. here's the correct manual for it: http://www.outboardbooks.com/index.cfm?fuseaction=models.main&year=1973&ID=52048
these motors, did not have the tale tell pee stream, to tell if the impeller was working, is any of the paint on the engine, pealing or blistered. this would be a sign of overheating, if so pull the head, and check gasket, also check for a warped head. and find the source of the overheat. impeller, or thermostat. will also give you a chance to inspect the cylinders. at the cost of a $20 gasket. and it's a lot easier to change the tstat with the head off.

 

[evinrude70hp]

Re: Johnson 50 very low compression on lower cyl.

decarb and if that doesnt help after letting it sit for 2 or 3 days pull the head off and inspect for a blown gasket.

 

[nautme]

Re: Johnson 50 very low compression on lower cyl.

Thanks for the response folks. I decided to try the easy way first. went and bought some MMO, seafoam and deep creep today. I put the piston at tdc and filled it full of MMO. I'll let it sit for a couple of days, run a decarb, and see what happens.

I have one more option.. I have a Johnson 60 sitting on an old 16' tri-hull, The boat's not much, but the motor ran like a top last month. I was looking at it today and thought I might try putting it on the pontoon if the above doesn't work. I'm guessing from looking, that the controls would also need to be changed. Also the steering set-up is different. The steering on the pontoon works through the tilt pivot, but on the small boat the steering cables hook to a post under the front of the motor. Would I also need to change the steering? Any thoughts appreciated.

 

[nautme]

Re: Johnson 50 very low compression on lower cyl.

Well, I ran another comp test after letting it sit for a day and a half in MMO, and very little change in compression, maybe 5 lbs.

Now I'm wondering whether to try to fix the 50 or try to change to the 60.(see my last post) I like the idea of 10 extra horses and the 60 really runs well. The only issue with it is sometimes when cold, it doesn't shift into forward very smoothly, kinda hesitates going into gear. It is a Johnson 60, model # 60ESL70D, ser.#U3322405. It is now on a 69 model Larson, 16', which is about done for.
Can anyone give me some insight on which way to go? I'm leaning toward the 60 if I don't run into issues with changing the controls and steering.
Any advice appreciated

P.S. By the way, I found no indication of blistered paint or any sign of overheating.

 

[F_R]

Re: Johnson 50 very low compression on lower cyl.

Pull the head and look. 15 pounds is next to nothing compression-wise. You will find out what to do very quickly when you take a look-see. I'm betting on a blown piston. But could be a blown head gasket if this is your lucky day.

 

[ezmobee]

Re: Johnson 50 very low compression on lower cyl.

Does the 60 have a tilt tube? My '73 85 has a tilt tube but it was capped off and the cable steering was hooked up to a tab on the motor like yours sounds to be. I switched to a modern rack and pinion system this year. I was able to connect the steering cable to my tilt tube and purchased a used "steering link bar" (eBay) to connect the tab to the cable end.

 

[licketdsplit756]

Re: Johnson 50 very low compression on lower cyl.

If Ya Got Some Compression Then Your Lucky. Dont Sound Like Anything Is Broken Just Worn. Bore And New Rings Is All It May Take. Not To Mention Time To Diasemble And Reasemble. Good Luck. Doing It Myself Right Now. Kindfa Fun Exploring Into Unknown Territory.

 

[nautme]

Re: Johnson 50 very low compression on lower cyl.

OK folks,
I pulled the head today and that lower half is toast. Top of piston looks like a pile of molten aluminum, as does the head combustion chamber. Cylinder walls badly scored, too bad to be bored. I've torn down a lot of 2 stroke motorcycle engines but have never seen anything this bad. Upper cylinder looks absolutely great, no carbon..just a little discoloration on the piston top. Why would the lower cyliner look so bad and the upper look so good?
Anyway it seems my best option now is to try to put the 60 hp on the pontoon. I don't see that much of a problem except the steering set-up. Sure could use some information and advice on the project.
Thanks

 

[offshore100]

Re: Johnson 50 very low compression on lower cyl.

OK folks,
Why would the lower cyliner look so bad and the upper look so good?

Thanks

Each crankcase/cylinder assembly is separate from any other in the motor, if the lower one wasn't getting fuel, it wasn't getting oil either.

As for steering, if your motor has that tilt tube, you're in business.

 

[nautme]

Re: Johnson 50 very low compression on lower cyl.

As for steering, if your motor has that tilt tube, you're in business.

Not sure what the tilt tube is. Like I said, I'm new to boating, The 50 has a tube running through the bracket that bolts to the transom and the motor tilts at that point. The steering mechanism runs through the tube and is hooked to a rod that turns the motor. The 60 has a solid bolt that runs through the pivot point and the steering cable is hooked directly to the motor. the bolt on the 60 appears to be a bit smaller than the tube that runs through the bracket on the 50.

 

[mikesea]

Re: Johnson 50 very low compression on lower cyl.

check the color of the engine harness ends,if the 60 is purplish and 50 red,you have a problem,unless you use other controls from old boat,some earlier engines had different harnesses,as for the steering,what you need is a cable mounting bracket that would attach to hull,I would imagine the boat thathas the 60 had or has one,it could be tricky on a pontoon boat if yours has the engine setting outboard of the transome,It is possible to get some newer model brackets that allow for a pivot,steering (different names ) tube,being the tube your 50 has to allow cable to pass through,It could take some labor and you need find a salvage yd.with old engine parts,not worth spending a ton of $$$$ on the process,another option,you might find a good used powerhead for your engine on ebay etc.Rebuilding the old one ,would probably be more costly than wort it,BUT,I believe there are short block rebuilds avail for sale through this site,a shortblock like a car.use your own electrical,carbs,starter etc.sorry you got a bad one,maybe the guy will humble himself and give you a few $$$.Its hard to tell if you got a blown cyl.without a comp tester,the motor probably had the idle turned up as to run ok on the hose,but as you know,no power under load

 

[rebuilt]

Re: Johnson 50 very low compression on lower cyl.

Don't know if you're interested, but..... There's a couple of decent looking 70's powerheads listed on eBay right now. Use Johnson 60 hp for your search criteria. One is an electric shift, not sure about the other one. Didn't research beyond that. Good luck, KR

 

[nautme]

Re: Johnson 50 very low compression on lower cyl.

OK folks,
I finished the engine swap and everything went pretty well...Not that much of a chore other than threading the cables through the little holes between the pontoons and the deck. My arms were too big to reach them so had to recruit the wife for that chore. Now I have a couple other questions.
The old boat had neither a tach or a volt meter, and the generator wasn't hooked up. I'm pretty sure the motor (the '70 model 60 hp) has a generator, but not positive. Can anyone explain how to hook them up?
Thanks to all you guys who helped me out.

 

[mikesea]

Re: Johnson 50 very low compression on lower cyl.

if the tach,voltmeter worked ok with the other motor at one time,then your wiring ,assuming you are using the same and the harnesses are compatable ,(which is why I posted about the possible differance earlier)you shouldnt need to do anything,the 60 will have a charging system,the grey lead from your harness is the pulse ,you want any power to your gauges to be off the purple which is the accessory,(on when running)blk is gnd,blue to the gauges is lite for nite running,hope I understood your questio

 

[nautme]

Re: Johnson 50 very low compression on lower cyl.

Thanks for the reply, Mikesea. Actually, I changed the control cables along with the motor, so all the wiring from the old boat is on the pontoon. The pontoon has a tach and voltmeter that the old boat did not have. The generator was not hooked up on the old boat, just had a cable from the + bat to the solonoid and a cable from the - bat to the motor ground...no other wires to the battery. I know it needs a wire from the gen (or regulator) to the bat to charge, just don't know which wire. I've got a manuel ordered but don't know when it will get here.
Anyway, I had the pontoon out on the lake this weekend to try the new swapped(used) motor. Everything went just like it should...motor purred like a kitten, steering was smooth and responsive, I was tickled pink.....for about 3 hours. Then the motor started to lose power exept at very low RPM, and gradually got worse until it finally would do nothing but idle. I limped back to the docks and pulled the plugs but they seemed to be OK, so I pulled the fuel filter amd it had a little trash in it so I blew it out, replaced and started the engine. She ran fine, I closed her up and headed back out and in about 2 minutes it did the same thing again. This time I pulled the engine cover off to check to see if I could see anything visually wrong. Within 30 seconds, the motor pick up and ran fine. I replaced the hood and it stalled again. So I ran all weekend with no cover on the motor. Any Ideas???? One guy at the Marina told me I needed to cut some holes in the cover so the engine could breath, but it seems to me that it needed holes the factory would have put them there.

 

[samo_ott]

Re: Johnson 50 very low compression on lower cyl.

Forget the guy at the marina! It probably has an exhaust leak on the powerhead and when the hood is on it's trying to burn the exhaust gases instead of fresh air. It's a common problem. Find the exhaust leak and fix it should solve the problem.

 

[mikesea]

Re: Johnson 50 very low compression on lower cyl.

Im trying to figure what your saying,is the engine so old it has an external generator,a 1970 60 hp would be a 3cyl loop charged and unless Im totally losing it the charging circut is under the flywheel and the same units that power the engine also charge the battery,or,is your engine one of the older 4 cylinder engines,pre 1970 ,I have to think you have the newer style,therefor it would be wired through the eng harness and the charging circut would be connected at the solonoid with the battery cable