Does this make sense

[orangeman]

The mechanic at our marina is not really a mercury outboard guy so I was hoping
someone who knows mercury could tell me if his diagnosis sounds correct. The engine is a 1983 115HP inline 6 SN6198924. The motor ran for a short time then quit and would not restart, it was idleing when it quit, seemed like no spark as it cranked good but never caught. The mechanic checked it out found no spark on any cylinder. He did eventually get it running but then it quit again. He removed the flywheel and found a scuff on the stator. He says the scuff is caused by excessive play in the top bearing and motor needs major surgery which he is not offering to attempt. I did wiggle the top of the crank and there is noticeable play in it. Does this sound like a correct diagnosis? Anything else to look for?

 

[This_lil_fishy]

Re: Does this make sense

Sounds like it needs a complete rebuild, with new crank bearings, and possibly replacement or refinishing of the crank itself. Would likely be very very expensive.

Ian

 

[Chris1956]

Re: Does this make sense

Orange, You may be able to replace the top main bearing w/o tearing the motor down completely. You will need to remove the flywheel, stator and starter. Now loosen the top crankcase bolts and remove the top end cap bolts. Gebtly pry out the endcap. Now a puller on the crank top bearing should pull it off.

BTW - check the 3/32" rubber hose and check valves to make sure they are clean.

 

[CharlieB]

Re: Does this make sense

First, determine the cause of the ignition problem by following the steps outlined in the Rapair/CDI Ignition Troubleshooting Guide. It very well may be that the stator is not making consistent voltage because contact with the flywheel will nullify the magnetic field and stator output should read intermittently.

In this case, replacing that top bearing IS necessary.

Check compression, determine if you need any other work.

 

[j_martin]

Re: Does this make sense

First, determine the cause of the ignition problem by following the steps outlined in the Rapair/CDI Ignition Troubleshooting Guide. It very well may be that the stator is not making consistent voltage because contact with the flywheel will nullify the magnetic field and stator output should read intermittently.

In this case, replacing that top bearing IS necessary.

Check compression, determine if you need any other work.

Don't do any more running or attempting to run until you fix the bearing. A light touch between the flywheel and stator, not enough to mash things up, will still cause a "magnetic short" and burn out the stator.

hope it helps
John

 

[orangeman]

Re: Does this make sense

Thanks so much for all the thoughtful replies. I was lucky to find this forum.
I'm interested in Chris's suggestion that the top bearing might be able to be replaced without breaking the whole motor down. I know that discussion is premature at this point but eventually I would like additional opinions on the idea. It looks like I need to do some legwork to figure out what to do next. I will get a manual and read up on the powerhead(any suggestions on best manual to buy?) I will also go up to the marina and get compression readings on the 6 cylinders to see if there are any problems in that part of the engine. J Martin any advise on how to get the compression readings without doing more damage? As of now the flywheel is off the engine.

 

[j_martin]

Re: Does this make sense

Thanks so much for all the thoughtful replies. I was lucky to find this forum.
I'm interested in Chris's suggestion that the top bearing might be able to be replaced without breaking the whole motor down. I know that discussion is premature at this point but eventually I would like additional opinions on the idea. It looks like I need to do some legwork to figure out what to do next. I will get a manual and read up on the powerhead(any suggestions on best manual to buy?) I will also go up to the marina and get compression readings on the 6 cylinders to see if there are any problems in that part of the engine. J Martin any advise on how to get the compression readings without doing more damage? As of now the flywheel is off the engine.

Pull the stator off, throw the flywheel back on, and crank it to get the compression readings.

Actually, at cranking speed you're not too likely to cause further damage if you leave the stator on, but at this point you're only 4 mounting screws and 6 wires from having it off.

Hope it helps
John

 

[orangeman]

Re: Does this make sense

Orange, You may be able to replace the top main bearing w/o tearing the motor down completely. You will need to remove the flywheel, stator and starter. Now loosen the top crankcase bolts and remove the top end cap bolts. Gebtly pry out the endcap. Now a puller on the crank top bearing should pull it off.

BTW - check the 3/32" rubber hose and check valves to make sure they are clean.

Chris where is the hose you are referring to and what is its function?

I subscribed to the seloc online manual and it is terrible. After reading through it I really don't have a good idea how the crank top bearing is installed. Does the end cap bolt to the block and crank cover? Does the bearing sit in a rabbet in the block?

 

[Chris1956]

Re: Does this make sense

The rubber hose runs from the bottom main bearing to the top main bearing. It carries excess oil from bottom to top, and lubricates the top main bearing.

The top (and bottom) main bearings sit in cast aluminum end caps. These unbolt from the block, but fit tight, so you need to loosen the crankcase bolts a bit to get 'em out. The top end camp usually has a brass shim under it. Save and reuse it. The top beaing will likely stay on the crankshaft. You may need a puller to get it off. When you install the new upper main bearing, put it into the end cap and carefully tap it home.

 

[orangeman]

Re: Does this make sense

The rubber hose runs from the bottom main bearing to the top main bearing. It carries excess oil from bottom to top, and lubricates the top main bearing.

The top (and bottom) main bearings sit in cast aluminum end caps. These unbolt from the block, but fit tight, so you need to loosen the crankcase bolts a bit to get 'em out. The top end camp usually has a brass shim under it. Save and reuse it. The top beaing will likely stay on the crankshaft. You may need a puller to get it off. When you install the new upper main bearing, put it into the end cap and carefully tap it home.

Now I can visualize how it goes together. Thanks so much. I just ordered the bearing and the o-ring. Have a few more questions if you don't mind.
How tight a fit is the bearing? Do I need to heat the inner race to get it on the shaft? Will I need to drive the bearing into the cap?

Thanks again for your help.

 

[Chris1956]

Re: Does this make sense

I do not think you need to heat the bearing to get it onto the crank. I think you can just carefully tap it to install. The bearing is a snug fit into the end cap. I would smear some grease on the oring before assembly to hep seal it.

 

[orangeman]

Re: Does this make sense

Here,s the latest. I finally had time to work on the engine. I was able to get down to the endcap and then get the endcap removed. Now I hit a brick wall,can't get the bearing out. I can't find any kind of bearing puller that will fit in there and be able to get a grip on the bearing. It is all the way down against the top crank with almost no clearance to get something underneath it( maybe 1/32 if i'm lucky. Any ideas I was able to rig something up to get some pull on it but it seems to be on there tight.
One other thing I noticed is that there does not appear to be much play in the bearing. I dont notice any real difference from the replacement I purchased. Could something else cause the fly wheel to scuff the stator and wear away the end of the timing pointer?
Any input would be appretiated.

Orange

 

[Chris1956]

Re: Does this make sense

Orange, Is the bearing a snug fit in the end cap? Is the stator damaged or rusted so it is not round? Those are the only things I would think would cause the crank to move around. Is the crankshaft straight?

You should be able to pull the main bearing, using a harmonic balancer or other similar puller. Try some thin eye bolts and see if you can hook the edge of the bearing, and thru the space between the ball bearings.

Alternatively, wrap some heavy wire between the ball bearings and fasten it to the puller. It should not be on that tight.