Rear motor mounts 1986 Mercruiser 140

[Jimmy H.]

Hi, I've just recently started my motor up for the first time in the boat with muffs. Was very shaky while it was warming up. I did find that the rear mount bolts were snugged but not torqued. I torqued them to 35 lbs/ft per the manual. It seemed better. I also noticed part of the bell housing was in contact with the deck so I chiseled some away to give some clearance thinking it was transferring vibration to the deck. I started it today and it is worse! It wobbles from side to side at idle, at 1000-1200 rpm is an extreme wobble (like the motor is going to snap off the rear mounts, at 1600+ rpm is very smooth. I know these motors are shaky but the worst part is so bad it cant be right.

I pry slightly with a screw driver between the deck and the motor and there is easy movement at the rear mounts.

The rear mounts I assume are worn and I will lift the motor and replace them if I know this is 99% of the issue. The mounts appear to be low in the motor housing and looking at it from the bottom there is a gap above the fiber washer which doesn't seem right. That is where the play comes from and it rocks like a son of a ...... gun.

Here is a shot from above. The mount seems low to me??

Here is a shot from below and you can see the gap above the fiber washer. Is this normal looking?

Thanks to anyone that can share some knowledge.
James

 

[Don S]

Re: Rear motor mounts 1986 Mercruiser 140

Wobble isn't caused by the mounts, it's caused by the engine not running right. That includes point dwell, then timing, compression check, good plugs and wires, cap and rotor, idle mixture and choke operation.

Especially the mixture, too lean, and it will shake a lot.

Is the back of the engine hitting something? Have you checked the alignment lately? Something is holding the back of the engine up, and it's not the mounts.

 

[Jimmy H.]

Re: Rear motor mounts 1986 Mercruiser 140

Thanks Don, more then glad to hear from you. I've just checked the alignment and this weekend was the first time a ran the motor mounted in the boat. The alignment bar went in and out with two fingers, splines were even all around.

I'm going to go and inspect everything right now. Are you saying that gap above the fiber washers is not normal? The metal on the motor mount should be sitting flush right on the fiber washers?
thanks!

 

[Don S]

Re: Rear motor mounts 1986 Mercruiser 140

You might want to recheck your alignment since you tightened the rear mounts. Then turn the engine a half turn and recheck the alignment.
Have you replaced the mounts or anything? I can't put my finger on it, but it just doesn't look right.

 

[Jimmy H.]

Re: Rear motor mounts 1986 Mercruiser 140

No the mounts were not replaced. New transom, stringers and deck however.
I agree it doesn't look right. I just went down and looked real close and there is no chance of the motor resting on anything. The double lock washer sits higher than the fiber washer and it appears it is just the mount sitting on the lock washer. Perhaps the gap is normal.

You are more than correct on the running. That makes sense it needs a tune up and cap,rotor, plugs, wires, dwell, timing etc.. changed and set up. Compression I checked out in the fall after running it in the garage and all cylinders were near even at approx 125 psi.
The choke may very well be not working properly, I'll be honest im not an expert when it comes to points and carbs but I need to get on it. I need to educate myself on all this and tune it up.

If you think of anything else to do with the mounts let me know. I'll go with they are ok and I think your dead on with the shaking being motor running related.
Thanks
james

 

[Jimmy H.]

Re: Rear motor mounts 1986 Mercruiser 140

I forgot to mention that it has been very hard to start even after it warmed up so a tune up must be in order. Running lean and shaking makes a lot of sense. So glad you chimed in and got me on track Don.
Thanks again!
James

 

[Don S]

Re: Rear motor mounts 1986 Mercruiser 140

The mounts are probably fine, never really looked at them that close up before.
As long as the alignment is ok after you torqued the mount bolts down, you should be good to go. After a tuneup that is

 

[achris]

Re: Rear motor mounts 1986 Mercruiser 140

The mounts are probably fine, never really looked at them that close up before.
As long as the alignment is ok after you torqued the mount bolts down, you should be good to go. After a tuneup that is

I agree with DON. Those mounts look fine. I would just add, did you put lots of water-proof grease on those bolts before you put them in? They look suspiciously dry to me. Have a read of THIS THREAD, and you'll see why they need to be greased.

Chris.......

 

[Jimmy H.]

Re: Rear motor mounts 1986 Mercruiser 140

Thanks Don and Chris, I will remove them one at a time and put the mercury 2-4-C grease on them. (i think that's what it is called). Hopefully that other post is the exception and not the rule. Every piece of wood in my boat was mush 9 months ago but no hardware was seized on the motor, gimble assembly, outdrive and especially not those bolts. Lucky I guess.

So now for the good news...
I dug up the manuals for the motor, carb, fuel system, ignition, etc...
Started reading through the carb one first which was also the smallest (bonus) and did all the checks in the first section.
First I didn't even know that "thing" attached to the carb was an electric choke.
2nd checked and cleaned the small filter between the fuel line and carb. (didn't know that was there)
finally adjusted the idle needle valve and upper idle screw as per the manual, pulled the boat out, hooked up the muffs and wham it started so easy. I shut it off after it warmed up three times and restarted it hot so easy it barley cranked over.
It was much less shaky just from that.
I know the final fine tuning adjustment for idle has to be done in forward gear while in water so I'll wait on that.
This week a tune up, points, cap, rotor, plugs and wires. Should do it I think. If I'm lucky and it even runs a bit better the shaking should be no more. (note I did change the oil and filter a few weeks ago before running it)
I'll report back after I tune it up and get it on the water.

Thanks,
James

 

[achris]

Re: Rear motor mounts 1986 Mercruiser 140

All sounds good... You need to do the ignition system tune-up before the fuel system. So when you've changed the plugs, points, cap and rotor, set the points gap/cam dwell and the initial timing, you'll probably need to go back and re-set the fuel idle mixture and idle speed.

Here's the list and order in which I do a tune.

So, in this order.

1. Compression tests.
2. Check spark plugs, replace if needed.
3. If points, replace, along with condenser and rotor. Check and adjust, if needed, points cam dwell angle.
4. Inspect distributor cap and leads, replace if necessary.
5. Check spark quality (needs to be a nice BLUE spark drawn over 1/2").
6. Set timing. Check timing advance is working correctly.

When all of these items have been done, THEN move to the fuel system....

Which manual are you using? A genuine Merc one, or one of the (less then accurate) aftermarkets?
Cheers,

Chris.......

 

[Jimmy H.]

Re: Rear motor mounts 1986 Mercruiser 140

ok Chris, sounds like a plan.
I have the oem merc manuals so I'm good there.
The compression was good less than an hour ago run time last fall.
Plugs and wires obviously are easy but the rest I have to admit I don't really know how to do. I'll go through the manuals and if you don't mind a few question throughout this week maybe you can help get me through it?
I am going to get all the tune up parts hopefully tomorrow and start replacing.
Thank you,
James

 

[achris]

Re: Rear motor mounts 1986 Mercruiser 140

ok Chris, sounds like a plan.
I have the oem merc manuals so I'm good there.
The compression was good less than an hour ago run time last fall.
Plugs and wires obviously are easy but the rest I have to admit I don't really know how to do. I'll go through the manuals and if you don't mind a few question throughout this week maybe you can help get me through it?
I am going to get all the tune up parts hopefully tomorrow and start replacing.
Thank you,
James

More than happy to....
And points, condenser and rotor are pretty easy too... No rocket science. (Invented over a hundred years ago!)

 

[dubs283]

Re: Rear motor mounts 1986 Mercruiser 140

Plugs and wires obviously are easy but the rest I have to admit I don't really know how to do.

click this link:

http://forums.iboats.com/mercruiser...ne-up-your-engine-points-ignition-335302.html

 

[Jimmy H.]

Re: Rear motor mounts 1986 Mercruiser 140

Wow thanks, that is a good link for me.
Based on that I think I will replace the coil also... looks a bit crusty and at this point why not replace it.
Some guys at work (Benz dealer) have dwell meters and timing lights so I'm good for tools.
I have parts on hold including points, condenser, cap, rotor, wires and soon coil.
I left the manual at home and I am at work today. Can anyone direct me on the proper type of spark plugs for my 140? It is 1986 era merc 140 4cyl. serial number #6903165

 

[achris]

Re: Rear motor mounts 1986 Mercruiser 140

Can anyone direct me on the proper type of spark plugs for my 140? It is 1986 era merc 140 4cyl. serial number #6903165

AC-MR43T or NGK BR6FS (you'll need 4 of them )

 

[Jimmy H.]

Re: Rear motor mounts 1986 Mercruiser 140

(you'll need 4 of them )

That I did know, I've been a service advisor for 14 years. Ten with BMW and 4 with Mercedes. I should clarify that I do know a bit about caps and rotors, points, etc... just never had a lot of exposure to it. Kinda old school I would say.
Anyways all parts are on there way to my work. Was $115 for everything and that just put the $1500 boat with the $3000 total budget just a hair over $6000 :laugh:

 

[Jimmy H.]

Re: Rear motor mounts 1986 Mercruiser 140

quick question. I didn't get any distributor cam grease with the new parts. should I sorce out some or use something more commonly available?
thanks

 

[achris]

Re: Rear motor mounts 1986 Mercruiser 140

quick question. I didn't get any distributor cam grease with the new parts. should I sorce out some or use something more commonly available?
thanks

A very thin smear of any good quality grease will do.

BTW, the comment about 4 spark plugs was very much 'tongue-in-cheek'...

Chris.......

 

[Jimmy H.]

Re: Rear motor mounts 1986 Mercruiser 140

I know, I know. Just bugging. Though most of our gas engine cars at work have two plugs per cylinder so you never know...

 

[Jimmy H.]

Re: Rear motor mounts 1986 Mercruiser 140

Plugs and wires obviously are easy

I knew when I wrote this it would come back to bite me!!!!!!!
Give me a bit, I'm uploading some pictures to show what I discovered. Shouldn't even be telling anyone this but you'll get a good laugh and the motor needed a tune up anyways. So rookie... so so rookie