Mercruiser 120 specs 1964- 72 Gm

[FishingTheFL]

Anyone got a manual with the valve lash torque, timing, and Carb settings?

Put a new CAM in... Now the boat will barely start unless I give it throttle to idle. When I try to open it up, the motor chokes out. The mechanic I got working on it says "the coil is bad. Some one hooked it up backwards"... Obviously it was him not willing to take the blame... He said " they don't last long when hooked up wrong". So I asked " how did I get 4 or 5 days use out of it then if some one else hooked it up wrong?" He never gave me an answer...continued to say it was fuel or spark...

Couple topics I read said it could be lash is to tight, carb needs adjusting, timing could be off... The coil is only $40 so I will start there today but if anyone has specs... I'd greatly appreciate it.

My motor is a 69 but 64-72 is there years for part listing...

Thanks for any help!

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[henrybud]

A cross reference is for a 69 Chevy Nova.  That may help you some.  I would call Bill at Independent Marine.  He is a wizard and knows that engine extremely well.

[Xxx]

If the valve lash is to much or basically to tight it can cause the engine to be in a under a load type scenario. I've even scene motors back fire through the carb. I don't think the coil is bad but there's really no way to check them, years ago guys had coil testers but over the years they went to the way side. Personally I would go with a oe coil these aftermarket ones, I've seen to many fail early to feel comfortable putting on auto parts store HY Fire type coil. Ok so there's two ways to adjust the lifter, "valve lash" motor is cold or the motor is hot, I do the cold way it gets it so close it hurts, then adjust them while motor is hot if it's necessary, but it can get messy of you don't have a set of these clips that go over the oiler hole on the pushrods/lifters keeps the oil from squirting all over. OK remove the plug wires, then the plugs & distributor cap. Crank the motor till the rotor points to #1 cylinder and the points are open, at this position both valves are closed. Make the adjustment to both valves, turn adjustment nut till all the lash is removed. This position may be determined by checking pushrod side play. Turn the push rod at the same time adjust the nut very slowly, when movement is felt on the push rod, "no slop and a slight movement like down" turn the adjustment nut 1 full turn, after you did this to both #1cylinders valves, crank the motor till its at #2 cyl and the point s are fully opened repeat the processes at #2 then #3&4 I assume it's a 4cylinder? Even if it's a 6 the same technique is applied. The point gap is .022 so might as well check that right away, just make sure the lobe is dead center or at its highest point, you'll see what I mean and you can turn the motor easy with no plugs in. Set the plugs at .035. Set your idle under 650 rpm so your not in the mechanical advance, then set timing at 8*BTDC that's after you put all the plugs and wires and distributor cap back on, listen to make sure you don't hear any rocker tapping noise if so just give that rocker a tad more on the nut, that's why I like those rocker clips that stop the oil from shooting all over, you can do this with the motor running. From what my books say both type carbs the idle mix screw is from all the way turned in, it should be at 1-1/4 turn out. Hope this helps ya out!! PAP!! 👠🎣 If ya need any more info shoot a pm!!

Edited September 20, 2016 by pap

[FishingTheFL]

Thanks pap. We'll give it a try after work

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[rolmops]

I've got a pile of manuals in this website. Check out if one is yours.

http://boatinfo.no/lib/library.html

Open the link and then go to mercruiser manuals. Manual #1  is the one you need

Edited September 20, 2016 by rolmops

[FishingTheFL]

Guy I have rebuilding this has never done dwell before... Any mechanics near not doing winterizing never Ovid area... Prefer somebody who knows what their doing figure it out...

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[rolmops]

Guy I have rebuilding this has never done dwell before... Any mechanics near not doing winterizing never Ovid area... Prefer somebody who knows what their doing figure it out...

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Try and talk to Lakebound88. He probably knows the best ones around

Edited September 21, 2016 by rolmops

[Bozeman Bob]

 You need a dwell meter or lose the points and get a petronix points conversion kit. You eliminate the yearly points and dwell drill. The kit has its own coil so the ohms are correct. Jegs - Ebay or google it. Probably 125.00 for the complete kit.

[FishingTheFL]

Specs for my motor. We set everything to spec. Except maybe dwell. He had dwell meter for a 6 and a 8 but not a 4 cylinder. Compression test said they were 149. 148 150 and 149. It would not idle and when we put it on the timing gun and it didn't show anything. He even tried another gun. Suppose to have Lake take a look at it. Looks like snow flakes before this tin can sees a good day of fishing.

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[rolmops]

when you set the timing,did you set it perhaps on the exhaust stroke instead of the ignition stroke?

[FishingTheFL]

I'm not personally doing it but I imagine he did that right. Basically what he is saying to me is that the timing gear is wrong or the marks on it are wrong by a tooth or two. He says the distributor lines up with the crankshaft at tdc. He says everything lines up by the marks on the gear, and crank gear, but it sounds like the valves are out of time. He wants to take it all apart and try to make sure it all matches the old stuff. The only difference I seen was that the old gear was fiber and the new one is aluminium. Fran from Barret is out of town so no brain to pick there. Should left the old camshaft in and went fishing

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[FishingTheFL]

Oh and the only other thing he mentioned was he forgot a metal shim that goes between the timing gear and the camshaft? But he says the gear will not move but it sure sounds like to me it could slide in or out putting the whole thing out of line... But what do I know...

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[FishingTheFL]

So I have a theory. Say we been assuming from the front side was #1(closet to the bow). What if its 1342 from left to right (stern to bow).

Also let's assume the timing gear has marks on both sides. What if he put the gear on backwards, wouldn't this put the cam lobes 180 off.... If he flips the gear over, then it would be right?

The only other thing I can thing of is the metal shim between the gear and the shaft. He says the gear is suppose to bottom out against it... Only 3 things I can think of after tons of reading and videos

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[stoneam2006]

Is the timing chain/belt new?

I have run into this on quads and thay if you don't replace the old chain true position is not know bc of strech. Have you tried advancing and retarding timing slightly? Does it make any difference?

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[stoneam2006]

And in my experience on other motors....if cam lobes were not in correct orientation you would be off and more than likely not even start. Timing being off a tooth or 2 could and more than likely would run...just badly

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[FishingTheFL]

We have tried both advanced and retarded. No difference. Didn't replace the chain.

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[FishingTheFL]

When I watched him install the distributor, its like it wouldn't drop in perfect. It would drop in mid tooth... That's why I question if the gear is on backwards. I don't even know if that's possible.

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[stoneam2006]

How does it sound when it is running? Any noise that may seem normal but wasn't there before or don't know if was

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[FishingTheFL]

It sounds better but it shakes hard and only runs with throttle. Dies out if it idles. Basically got rid of a tick to have an non operative motor... Old gear was fiber new one is aluminum. Don't know if I mentioned that

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[stoneam2006]

When I watched him install the distributor, its like it wouldn't drop in perfect. It would drop in mid tooth... That's why I question if the gear is on backwards. I don't even know if that's possible.

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Idk if it is either to be honest. But seems as if it wouldn't the gears down below have to be the problem. Either backwards clocked one way or the other maybe that spacer he forgot is allowing the gear to shift inward so it's binding up. I don't have much boat experience but lots of quads and bikes and motorcycles and from what you describe it sound to me like timing

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[stoneam2006]

It sounds better but it shakes hard and only runs with throttle. Dies out if it idles. Basically got rid of a tick to have an non operative motor... Old gear was fiber new one is aluminum. Don't know if I mentioned that

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Yea that shouldn't make any difference. In your opinion does it seem to be starving for fuel? How are plugs? Start it and let die and pull plugs are they wet? Is the carb vacuume assisted or anything like that.

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[stoneam2006]

Shakes hard sounds like starvation. Just barely enough combustion to push back to top.

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[FishingTheFL]

Plugs are covered in black but not wet

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Edited September 23, 2016 by FishingTheFL

[stoneam2006]

That's not good either...has carb been rebuilt?

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[stoneam2006]

I think I would change or clean plugs see if they go black right away again...black is rich or burning oil causing carbon which I guess could be from valves being tight meaning open to long allowing oil to get in. Did you replace valves? Or pull out at all? How does it turn over when starting seem normal or seem like extra force needed? I'm no professional but I like to brainstorm with motors

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