1989 Johnson 150 GT--Compression Issues

[meangreen92]

Ok, I one cylinder with -0- compression...2 questions...

1. When looking at the motor from the drivers side and looking at the cylinder that has no compression...About 1/2 up the motor, where the motor mounts together, I can see bubbles coming out where the motor mounts together...This is only down where the cylinder is that has -0- compressoin...Is this related, can it be fixed, or am I in for a rebuild...

2. I am on a budget (3 kids and a handicap father I take care of) and not real concerned about the boat operating at max performance, just need to be able to take the kids fishing and get around the lake safely...Can I just replace the piston if this is what is wrong or does it require machine work? I am not wanting to totally rig it, but do not mind doing a little "engineering" to possibly get me another year or 2 out of the motor and hopefully will be in a position then to upgrade...

Let me know...Also, if anyone knows where or if I can get a used powerhead let me know...Of course, if the price is right and the source seams to check, I am willing to take a risk on a used one...

To say up front, I will not be able to afford to do a complete rebuild or buy a new motor...So my options are, repair the one cylinder or no fishing or boating for close to 2 years...It is what is, but my kids sure had a blast in this boat last year not only fishing but tubing as well...

Thanks in advance and I respect all responses...

 

[emdsapmgr]

Re: 1989 Johnson 150 GT

Re: 1989 Johnson 150 GT

A little hard to understand your description of "bubbles coming from where the motor mounts together." Do you mean bubbles between the head and the block, or do you mean where the powerhead bolts to the midsection? If you have bubbles coming from between the head and the block, you may just have a blown head gasket. Those are relatively inexpensive. If so, pull that head off and have a look. When you have the head off, check the gasket sealing ring to see if it is damaged/broken. If the head and piston are pitted, that's a bad sign. You will have to tear down the engine and replace at least that piston and it's ringset.

 

[meangreen92]

Re: 1989 Johnson 150 GT--Compression Issue

Re: 1989 Johnson 150 GT--Compression Issue

It is the midsection I believe...I will doube check, but I am pretty sure it is not at the headgasket...Sorry about the description, tried the best I can

Thanks for the help...Like I said, I am looking for as much input as possible as I am going to try my best to get this motor running as cheap as possible...I know it may not be the smartes thing, but it is my only choice...

Thanks again...

 

[emdsapmgr]

Re: 1989 Johnson 150 GT--Compression Issue

Re: 1989 Johnson 150 GT--Compression Issue

There is a gasket between the powerhead and the midsection. On the V6 engines, it is unusual for that gasket to fail. Much more common on the V4 crossflows. It seals the water pump passage and the exhaust passages. Anyway, any bubbling there probably is a separate issue from the zero compression cylinder. Best to pull the head off the side with no compression and have a look. You will want to move the piston around in the cyl and see if the outer ring is intact. Also, check the cyl walls for scuffing-aluminum transfer from the piston side to the cast iron liner wall.

 

[wilde1j]

Re: 1989 Johnson 150 GT--Compression Issue

Re: 1989 Johnson 150 GT--Compression Issue

Usually zero compression is bad news. Pull the cylinder head on the bad side. If you're very lucky, it'll be only a new head gasket needed. Look for scored cylinder wall, etc. And get an OEM shop manual. Too many things for us to lead you through all. Let us know what you find.

BTW, is it leaking at the crankcase parting line? Either take a picture and post it or learn terminology, so we know what you're talking about? Very hard to know what you're trying to tell us. Zero compression might be related. An air leak into c case will cause lean running, which can destroy pistons, etc.

 

[meangreen92]

Re: 1989 Johnson 150 GT--Compression Issue

Re: 1989 Johnson 150 GT--Compression Issue

Alright, this is where I am at now...I pulled the head, the piston outer wall is burnt and beat up, but what I could see of the ring did not look bad...The cylinder wall is scuff up very little in one spot, the rest looked perfect...I know the scuffing is not good...

The bubbles issue I spoke about has been addressed, got a guy that figured it out...Sorry for the bad description on that...

I have heard of poeple either ohming it out a little and going back with a bigger ring and same piston...Has anyone tried this with success...

I have a friend that has done work like this before (not just like this situation, but has ohm cylinders and replaced pistons, rings, etc...) and will help me, so the labor will be basically free (I am plannig on paying him something if he will take it)...

Here are the 4 options I am condidering trying...Let me know your thoughts please on what will give it the "best" chance of giving me another year or two...I understand there are no guarantees and this will be risky no matter what I do...

1. Ohm it out and put a slightly bigger ring in it, same piston...

2. Ohm it out as little as possible and go back with same ring and piston if we do not have to ohm it to much...

3. Get it bored out and put a new piston sleeve in and new piston, rings, etc...

4. Trash it and be without a boat for at least a year probably 2...I do not see a big financial change in my life anytime soon and will take me at least a year to save so money...(do not think I can take it)

Another other options/ideas would be appreciated as well...

Thanks again guys for all the input...It is really appreciated...

 

[blimp]

Re: 1989 Johnson 150 GT--Compression Issue

Re: 1989 Johnson 150 GT--Compression Issue

your best bet is to tear it down, bore out that cyl to 1st oversize (they sell pistons and rings in oversizes, you will want to take it to a real marine machine shop for this, its not too expensive either, usually around 30-50 per hole) and replace all the rings, seals, gaskets. You'll have a practically brand new motor for about $400-500 in parts and machine shop costs. You will want to hone the rest of the cyl when you put in new rings, the machine shop can do this or you can.

 

[meangreen92]

Re: 1989 Johnson 150 GT--Compression Issue

Re: 1989 Johnson 150 GT--Compression Issue

Just to clarify, if all the other pistons look new and those cylinders are still holding good compression, do I need to change those pistons, or just the rings...I priced it and am inline with your suggestion unless I change all the pistons also...Is there a need for change the piston all the good cylinders if they look good...I want to do what is needed by that gets the price up there quickly...

I called and marine machinist and will be taking it to them to check all the cylinders, hopefully just hone them and bore the one bad one...Replace the rings on all, replace the one burnt piston (sizes depending on the bore size), and roll forward...Just making sure this is what you were suggesting...

Sound like a plan???

Thanks again...

 

[blimp]

Re: 1989 Johnson 150 GT--Compression Issue

Re: 1989 Johnson 150 GT--Compression Issue

on my recent rebuild i replaced all the rings and only 1 piston. Many people will tell you to replace all of em, but i'm cheap

Some people won't bother rebuilding without all new pistons, rings, bearings, seals, etc, but if you are on a budget, just replace the one piston and all the rings. Make sure you inspect the rest of the pistons very carefully. I *would* recommend a seal kit, that upper and lower crank seal can cause issues and they are cheap.

 

[emdsapmgr]

Re: 1989 Johnson 150 GT--Compression Issue

Re: 1989 Johnson 150 GT--Compression Issue

It depends on what condition the cyl walls are in on the bad cyl. If there is aluminum transfer onto those walls, that can be cleaned up with careful use of some muratic acid. Depending on measurements, you need to determine if the walls of that bad cyl are egg shaped and if there is too much taper to them. You might be able to salvage that cyl as is by just honing it. If you do overbore, you can do just one hole and get one new piston. I am a fan of using all new ringsets, though, as blimp suggested. Yes, you will need a new powerhead gasket kit. New thermostats and a new impeller are always a good idea on a major rebuild. Also, replace all 6 of the water diverters in the powehead-those small rubber hoses in the block. You need to determine the reason for the initial failure. It is possible that you may have some dirt/debris in the jets of the barrel that feeds that cyl.-causing a lean condition and the resulting failure. An autopsy on that carb is a good idea. Or maybe it was an overheat on just that one cyl? You need to go looking for the reason the engine failed to make sure you correct it before running the new powerhead.

 

[boobie]

Re: 1989 Johnson 150 GT--Compression Issue

Re: 1989 Johnson 150 GT--Compression Issue

The big "Trick" here is to find out why that cyl failed. If you don't find out, you can rebuild it and may have the same problem all over again.

 

[meangreen92]

Re: 1989 Johnson 150 GT--Compression Issue

Re: 1989 Johnson 150 GT--Compression Issue

I was told today not to put rings on an old piston...

See quote:

"It is very bad JU-JU to re-ring old pistons. The new rings will do one of three things. Lock in the ring groove on the piston, misalign the piston in the cylinder causing piston slap or cut gouges out of the cylinder walls, Either of which means another rebuild. If you are just wanting to make a few more trips. Then bore the bad cylinder and install an oversize piston and don't do anything with the other holes. Whatever you do, do not hone any hole and put back the old piston."

How long ago did your do your rebuild with new rings on old pistons and how long has it lasted...I am cheap and broke, but do want to do the best thing possible for the money I spend...Please let me know your thoughts to quote above as before I was told the quote above, my plan was to put new rings on the old pistons, and replace the one piston...The only difference is, I may not hone them and just leave them as is since compression is good on them, that might be where he is coming from...Makes a major difference in price replacing them all...

Thanks again...

 

[meangreen92]

Re: 1989 Johnson 150 GT--Compression Issue

Re: 1989 Johnson 150 GT--Compression Issue

Regarding the quote I have in the above post, does anyone have an opion yeah or nay...

Also, Blimp, you replaced the rings, did you hone the cylingers or just install new rings on existing pistons and leave it alone?? Also, how old was the motor you did the rebuild on?

Thanks again...

 

[blimp]

Re: 1989 Johnson 150 GT--Compression Issue

Re: 1989 Johnson 150 GT--Compression Issue

mine was an '87 90hp, v4. I honed all the cylinders and installed new rings. Just make sure you clean out the ring grooves VERY well, measure the tolerances of the ring gap and between ring and the side wall of the ring groove and make sure it is to factory spec as well.

 

[emdsapmgr]

Re: 1989 Johnson 150 GT--Compression Issue

Re: 1989 Johnson 150 GT--Compression Issue

Factory manuals clearly state that reusing old pistons is acceptable if they meet certain criteria. They indicate that they must be cleaned of carbon, esp the ring grooves-and they describe the cleaning process, prior to reassembly. They also dictate the use of new ringsets.