Mercruiser 120 specs 1964- 72 Gm

[FishingTheFL]

Yes new valves. Here is a list of new parts we put in it.

Head gasket

Valve gasket

Rocker cover gasket

Camshaft

Valves

Timing gear

Plugs wire

Plugs

Coil

Condenser

Points

Exhaust elbow

All exhaust gaskets

The head gasket was blown out between #1and #2. Guy in port Byron said that was common with these motors. Same with those lobes wearing down

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[lakebound88]

When you out in the new hydraulic lifters, did you prefill them, and adjust the valves or just install, adjust and now have problems running. Valves can be way too tight if this is the case. We'll talk more.

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[FishingTheFL]

He used a drill to pump oil up threw the lifters. He adjusted then did it again to double check. The only thing I can think of is he didn't put that metal shim in and that is putting the distributor off.

I'm going to get the old cam and old fiber gear back today.

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[FishingTheFL]

Also when it turns over the start rings like a bell on the fly wheel. Mind you we didn't have to pull the motor because it is basically all open.

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[Xxx]

It sounds to me the timing is a tooth off one way or another, that's the only way it will run kind of sort of, sometimes it's a **** to get that distributor to drop in perfect, the only way to be sure is if the distributor is in righ is if it's pointing at #1 cyl and the points are closed, take the valve cover off and make sure both #1 cyl.valves are closed, this is bullet proof that the timing is right. If the timing is correct, certain motors MCM 110/120 is 1234. The MCM120M is 1342. Need to find out what the hell motor is in your boat first!!

[L&M]

Regardless of engine ci. or hp the firing order is 1-3-4-2 on GM based 4cyld MC engines.

[FishingTheFL]

Serial is 356836 on motor.

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[FishingTheFL]

Pap, I will take the valve cover off and rotate the motor until both valves are closed then see where the rotor is. If the rotor is off I just take the distributor out and rotate toward the #1 mark he made? I'll take pictures here shortly

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[FishingTheFL]

Immediately I notice.... He has the wires 1234. From front to back. He has the red wire that comes from the distributor to the coil on the negative side( red means positive with out a stripe correct?) If the wires are wrong then the lengths are wrong and the timing of the #1 cylinder firing will be off ? I have to take the distributor out, and coil off to get the vavle cover off. Can I tell by taking the rocker cover off?

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Edited September 23, 2016 by FishingTheFL

[stoneam2006]

Immediately I notice.... He has the wires 1234. From front to back. He has the red wire that comes from the distributor to the coil on the negative side( red means positive with out a stripe correct?) If the wires are wrong then the lengths are wrong and the timing of the #1 cylinder firing will be off ? I have to take the distributor out, and coil off to get the vavle cover off. Can I tell by taking the rocker cover off?

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Maybe someone with more experience than me can chime in but I fix the firing order first and try again may be the problem

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[Shellback]

Rotate the engine in the proper direction. Watch for the intake valve opening. Once it opens, then starts closing, continue rotating until the top dead center mark on the crankshaft lines up with the timing mark plate. The distributor rotor should now be at #1 cylinder. The missing shim shouldn't affect timing, but it could cause irregular wear on the cam or lifters.  All this cam and distributor timing is pretty basic mechanic stuff. Nothing high tech about it. If the engine ran half decent with the bad cam, you shouldn't be having these problems if the job was done properly. I'd have to question your mechanic's abilities. Some motors oil pumps are driven off the distributor. If the distributor doesn't drop all the way in, you may have to rotate the engine some for everything to line up. Once it does drop all the way in, rotate the engine again to make sure all the marks line up. You will have to rotate the crankshaft twice to bring the distributor back to #1.

[FishingTheFL]

I changed the plug wires around to what made sense to me. If #1 is at the bottom right, then #2 wire would be bottom left yes? If that's the case i put the wires to that order, which it sounded better, didn't fire up, but also sounded like it was under pressure. The battery is dying and looks like some rain moving in.

When I rotated the crank so the mark matched the timing cover mark I took the the distributor top off and the rotor is exactly 180 off from his marks for #1 cylinder. Is the distributor just in 180? Also the positive that goes from distributor to coil is connected on the negative side of the coil.

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Edited September 23, 2016 by FishingTheFL

[Shellback]

Do you know which direction the rotor turns? If it's clockwise the firing order is correct. If it's counter clockwise, the firing order is wrong. 

[FishingTheFL]

No I don't. How do I tell? Sorry, I'm jumping in now because I have a better understanding then I did and its already messed up... So worst I can do is put the plugs in wrong order and make the timing worse right?

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[Shellback]

You have to stop guessing. Turn the engine over until top dead center comes up on the pulley on the compression stroke. Also watch what way the distributor rotates. Once on top dead center, drop the distributor in so the rotor is pointing at #1. Then make sure the firing order coincides with the direction the rotor turns. 

[Shellback]

Keep in mind a four stroke engine's crankshaft rotates 2 times for each rotation of the camshaft and distributor. The timing marks have to line up when the engine is on the compression stroke. You can do this by way of watching the intake vale open as I said in an earlier post, or if you can bump the starter with #1 plug removed, you can feel compression coming up with your finger.

[Xxx]

L&M is the best boat mechanic I know he said the firing order is 1342. I'd bank on that!! So first put the plug wires on right. That motor is clockwise the #1 cylinder the the next wire goes to the 3rd cyl next wire goes to the 4th cylinder and last should be the #2 cyl the color grey wire should be going to the coil with a black going into the distr. The positive side on the coil should have a purple/yellow wire and a purple resistance wire running from the positive side of the coil to the ignition, only black running to the distributor. Here's a pic that should help ya

[FishingTheFL]

When I get home I'll make sure I rotate it to tdc. And see where the distr. Rotor is. I'm pretty sure our mechanic did all that. I'll update when I get home

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[rolmops]

The picture with the plug wires has the correct sequence. Right bottom 1 left bottom 3 left top 4 right top 2. If you think that he did a 180, you should try right bottom 4, left bottom 2,left top 1 and right top 3.

[FishingTheFL]

If the picture pap posted is right I know his plug order is wrong.

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[Xxx]

I had one of those, 120hp in a 18ft Sea-Ray, that I did a total rebuild on years ago. I knew I had the Manuel I just had to find it,once I couldn't be sure of myself, this guys been through the ringer already!! I hope you have a rubber mallet to adjust his mechanical mind. LOL. Good luck, with it. The only thing that's bugging me is that washer, because they only allow .002.-006 run out with the washer??

[FishingTheFL]

I personally think its the missing shim also. If the gear is in to far or out to far it would put the teeth off as well in my head anyway. It started raining so I'll check it all out tomorrow. Nick is suppose to look at this weekend but I'm getting a pretty good understanding after all your help and Fran from Barret.

Fran said bring it up to tdc. Then rotate the cap backwards til I see it spark with the key on. Tighten it down and it should be timed right without using a timing gun. I didn't quote him because I may not of said exactly what he said. Who knows it might just be the plug wires in wrong order but I still think its the shim missing screwing this all up

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[Xxx]

You'll be alright, Nick's a good man, now that I think about it didn't those motors have a nylon gear? Maybe the close tolerances on the run out might be that way to save those nylon gears, the new are metal, so it may be more tolerable. But it doesn't take much to jump the chain or constant wear on either side. I'd ask Nick about that.

[FishingTheFL]

The old one is fiber and the new one is aluminum. Waiting is what I'll end up doing. Plenty of stuff to do before the snow flies

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[rolmops]

I can understand why you may think that yours has the wrong sequence,but in a distributor the #1 cylinder is usually at the right hand bottom, while pap's picture shows #1 at the right hand top. At the same time it really does not matter where you put the #1 in the sequence as long as you make sure that the spot on the distributor that you use is where the ignition at tdcd -8 for #1 is at.That the engine fires up is a sign that the sequence is correct, or it would have backfired if it started at all.

Also, the rotation is clockwise. 

Edited September 24, 2016 by rolmops