timing "vs" bad bearings

[boltbreaker]

Hello everyone. I first want to thank all of the KNOLEGEABLE people who take the time to read through these threads. I truely enjoy working on outboards and iboats forums.<br /> Here's the pickle!:<br />I recently acquired a BEAUTIFUL 1973 9.8HP Mercury outboard. It has 120#'s of compression on both cylinders and looks like it has been VERY WELL taken care of. It's very clean, and I'd rate the paint and decals a 9.5 or better out of 10 and the motor hasn't ever seen saltwater. I can't seen any signs of overheat, or abuse.<br /> One little hitch. It's a little hard to start and seems "bogged" down when running. It sounds fairly good at 1/2 to full throttle, but as soon as the rpms start to drop she starts to clank around(sounds like a knock),vibrate, and die.<br /> The history of the motor and other "clues":<br />The prevoius owner stated he picked it up at an auction for $200. I can't say I blaim him, it's a nice looking engine. He took it to his local repair guy and the man put some "insulators" under the flywheel, a new impeller, charged him $250 and said it had a rod knocking and wasn't worth fixing. I spoke to the high priced repair man and asked him if he checked the timing and he said he didn't and verified the "insulators" repair. I don't trust his diagnosis and want to find out for myself.<br /> I noticed someone painted a white vertical line on the flywheel indicating that the timing has been tampered with at one time or another. <br /> I just acquired a dial indactor that screws into the spark plug whole and have a timing light on the way if that helps. <br /> Anyone have an ideas on how to check out the bearings without tearing down? I recently acquired a dial indicator that screws into the spark plug whole and a high priced timing light that hasn't arrived yet if that helps. <br /> I'm willing to tear this one down if it's what it takes to save the engine, but want to avoid uncessary repair if possible. I hope maybe I'll get a chance to play with my new tools and she's just sparking at the wrong time.<br /> All reponses are greatly appreciated!

 

[WillyBWright]

Re: timing "vs" bad bearings

Remove the sparkplugs. Place a pencil (eraser end) into the hole to rest on top of the piston. Find where the piston is midway thru the stroke. The other piston will also be at midstroke. Replace the pencil with your dial indicator with a long enough extension rod to meet the piston. Rock the flywheel back-and-forth and note how much movement it takes to get the needle to move. Repeat with the other cylinder. If one takes a whole lot more than the other, you found your problem.<br /><br />Those "insulators" you seem to be lambasting the mechanic about are very prone to leaking voltage thru cracks which DO occur over time whether the motor is used or not. This leads to weak to no spark and bad misfiring if you can get it to run at all. His repair was most likely completely appropriate. He got it running for the first time (probably in many years) and found a serious problem and stopped. That's perfectly appropriate as well. With these things, the only way to find certain problems is when the motor is running. It's certainly not His fault the guy before you bought a can of worms. He saw a clean motor with potential and found the mechanicals of the machine left much to be desired.<br /><br />The problems with old motors that have rarely been run are Legion. Internal rust and bearing surface pitting are almost certain, the water pump impeller hard as a rock. The fuel pump diaphragm, too. The seals could be rotted and cracked, gaskets dry and shrunken. The carb is most assuredly varnished. Frankly the fact that it "Looks" nice means absolutely nothing. It's quite possible that it needs a complete overhaul. It's also quite possible that it isn't practically savable. Sorry, but with Any old machinery, Looks are definately not everything.

 

[Chinewalker]

Re: timing "vs" bad bearings

If the motor runs as is and does indeed have a bearing knock, then it is still worth fixing (in my opinion). There are LOTS of those little Mercs out there lacking lower units and many more with marfed up ignition systems. Your motor seems to have a decent unit and obviously has spark, since it runs. Find a good short block, or the like with a good crankshaft and rods and you'll be good to go. If compression on your existing powerhead is okay, then it's likely that the bearings haven't exited the crankcase to eat up a piston, so it might be as easy as transplanting a crank, one piston/rod assy. and reassembling....<br />- Scott

 

[WillyBWright]

Re: timing "vs" bad bearings

I did an overhaul on a 20Hp of the same era and in similar condition. The owner knew it would cost more than it was worth and he was okay with that. It needed a bearing, but we did rings and seals. Crank was okay. He was full of smiles when we fired it up for him. I think he was happier than if he'd just bought a new one. And like yours, a very durable motor.

 

[boltbreaker]

Re: timing "vs" bad bearings

I tried the pencil and dial indicator thing. It really doesn't take that much movement to get it moving, and is the same on both cyl. Feels about the same or less than what I've seen 8 HP omc's that ran good. I'm still hoping it's in the igntion system, hopefully maybe the timing. Time to get out the book and start looking for specs I guess.<br /> I can't imagine this motor having a bad bearing with as good as it looks and feels!(maybe this is just denial)

 

[boltbreaker]

Re: timing "vs" bad bearings

The plot thickens…<br />I identified the outboard as a 1972 9.8 HP serial number 3364186 with the “phase-maker 2 ignition system”.<br /><br />I pulled the flywheel to take a peak and it doesn’t look like the parts have been replaced anytime soon but have been tampered with at one time or another(could see a little rounding on the slot screws).<br /><br />I have a clymer and seloc manual that covers the motor. Their specs vary(big surprise).<br /><br />I’m a little confused on conversions from my mulitmeter to the specs in the manuals. The manuals tell me to test at the R x 100 and r x 1000 settings. My cheap mulitmeter only has 200,2000,20k,200k,2000k settings. I’ve tried to figure out conversions in the past and the best answer I could find was the different setting just change the decimal point on the mulitmeter(this was the manufacture).<br /><br />I think the low speed coil is bad, but would like a second option before I “throw” parts at it.<br /><br />The first part of the testing according to Clymer is “Connect an Ohmeter to the red and yellow test leads. With the ohmmeter on the r x 100 scale it should read between 32-40 ohms(1972-1973) or 5.1-6.1 ohms (1974-on).<br /><br />The first part of the testing according to Selco is “Use the VOA range at R x 100 and check the low-speed resistance between the red and yellow coil leads. The reading MUST <br />be 32-40.”<br /><br />My test concluded 4.6 at 200 or infinities at 2000 or 200. No reading was taken from the 200k or 2000k settings.<br /><br />I hate to post what the second readings were….until I can “figure-out” the proper conversions. I don’t want to create unnecessary work for the person taking time to read through all this. <br />I'm trying here!<br />A BIG THANKS TO THE PERSON(s) WHO REPLY.

 

[boltbreaker]

Re: timing "vs" bad bearings

Am I thick skulled?

 

[booka]

Re: timing "vs" bad bearings

Boltbreaker<br />The settings on the multimeter indicate the max ohm reading for that position.Try to keep the range as close to specs as possible. Higher ranges = higher error factor