1972 65 hp Mercury 3 cyl Flywheel Timing Issue

rdmotors

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Ok I know that sounds weird but here is the problem to question.
I have a old 650 merc that has been well used but has great compression. The running of the motor is good but at idle the engine revs like crazy, pop it in gear and it runs good. I just want to get the idle down to a reasonable level, sounds like its in the 2000's. I have backed off on the idle screw to the point it is not touching. Rebuilt the carbs thinking I had a stuck float. Cranked the timing screw in and I started to get some kind of response to the adjustments. Still it revs to high so got to looking for a timing adjustment in all the books and web pages. Found out tho that the flywheel has been taken off of the timing belt gear and put back on. So here is the problem I dont think it is anywhere near correct. Can anyone tell me the relation of top dead center on number one pistion to the "keyway" on the crank shaft. Mine points to the casting line on the top rear of the motor. Then keyway to the flywheel if it is lined up with sticker top dead center or sticker to pointer on the side near disturbor top dead center. Then I need to know if you advance to 23 degs at pointer then time the dist. gear.
I know the whole flywheel timing being off makes a mess of things but the motor has been worked on by many less able than even me.
Oh I know this is my first post but this forum has helped me fix a many of motors in the past. Noteably and choke problem on a pesky 85hp Evinrude. Just got to get them tight is what I found out here and fired the first time after that. Want to say thanks for all the help.
 

sutor623

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Re: 1972 65 hp Mercury 3 cyl Flywheel Timing Issue

Do you have the manual? If not I do and wouldnt mind looking up the timing specs for ya. It can be an pain in the arse to get the carbs, dizzy, and flywheel to all mesh in sync on these motors. But once they do, WATCH OUT!!!
 

rdmotors

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Re: 1972 65 hp Mercury 3 cyl Flywheel Timing Issue

No i dont have the exact manual for that model year hp. I do have a clymer manual for 64-71 up to 135 hp. I guess since this one does not tell me the relation of the flywheel to the timing belt driver sprocket, the 71 is not as close to a 72 as I would have thought.
Yes I am finding out that the Mercury's have their certain little things with them that make them unique. All the rest of the motors I have worked on have theirs also. I do find the carburetors on the Mercurys are alot more forgiving than the Johnson/Evinrude. If the J/E has sit anytime what so ever the carbs most likely need cleaning. So far the Mercs I have run into not so much. I now give them a try first before I determine the fate of the carbs.
 

sutor623

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Re: 1972 65 hp Mercury 3 cyl Flywheel Timing Issue

Yeah I try EVERY motor before I do anything to it. (Unless it is in obvious non-running condition) That way I dont start digging a hole that doesnt need to be dug. It also sucks to order some parts only to find that you need more. I have a 1967 65hp 4 cylinder, and there is a mark on the distributor cam/pulley and housing that need to be lined up. Also there is a painted white line on the flywheel that needs to be lined up with TDC on the marker of the motor. If you remove the #1 spark plug, you can see TDC of #1 cylinder when the cylinder is closest to the head. That is where you want everything to be before you get the belt on. Once at that point you can make minor adjustments to the timing before putting the belt on. (I wish Merc had an aftermarket adjustable distributor cam gear, that way you could put the belt on wherever and just make small adjustments to the cam gear similar to a cars engine)
 

rdmotors

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Re: 1972 65 hp Mercury 3 cyl Flywheel Timing Issue

Thank you for your info that is what all the books are telling me also. Only here is the catch.....my flywheel has been removed once before by someone else. You say ok no problem just check if it is sitting on the keyway correctly, but my flywheel has eight bolts on top fastening it to the "hub" that has the keyway to the crank shaft. So the flywheel can be bolted on eight different ways and nether one of two piecies, hub or flywheel, has a mark to position them to each other. So here is what i did with the the flywheel off.....
I put piston one at top dead center
Slipped hub onto the crank shaft, which the "keyway" was pointing to rear of motor
put the flywheel onto the hub aglining the top dead center to the plastic pointer on the side of the motor....
in which the pointer is missing off of this old motor so i guestimated it
now i am turning the motor 23 degs on the flywheel to the pointer, i guestimated that postion also, then I timed the disturbotor and installed the belt
Now when it gets warm I will roll it out the shop and try it again
Hope that this time I am closer than I have been before......will see around lunch should be Above 50 by then
 

mnRIVERrat

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Re: 1972 65 hp Mercury 3 cyl Flywheel Timing Issue

I own two of these motors, a 73, and a 74, and if your flywheel timing is drastically off it wont run at all, let alone well. If you don't have an answer by tonight I can look at one of mine at home tonight and let you know.
 

mnRIVERrat

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Re: 1972 65 hp Mercury 3 cyl Flywheel Timing Issue

from my manual

6-8 MODEL 650 1970 - 1971
MODEL 800 1969 - 1972
MODEL 850 1973
Belt Timing
1- Remove the engine cowl. Observe
the straight line mark on the flywheel and
the arrow on the distributor magneto pulley.
When the flywheel mark is aligned with the
arrow on the pulley, the No.1 cylinder is at
top dead center (TDC). Remove the cap
screw, washer and plate from the pulley.
Remove the magneto belt from the pulley.
Slowly rotate the flywheel until the timing
mark on the flywheel aligns with the center
of the crankshaft and the center of the
distributor pulley. In this position, three
items are aligned -- center of crankshaft,
timing mark, and center of distributor pulley.
Now, rotate the pulley until the arrow is
aligned with the flywheel mark. Hold the
pulley in this position and install the belt.
Install the plate, washer, and cap screw to
the pulley. Tighten the cap screw to a
torque value of 60 in. lbs (6.78Nm).
 

rdmotors

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Re: 1972 65 hp Mercury 3 cyl Flywheel Timing Issue

Well tried the settings above and its back firing thru prop.....So will try setting the arrow on the dist to the crank shaft....stay tuned and will see if that works. Still not sure about the flywheel to hub timing...........
 

mnRIVERrat

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Re: 1972 65 hp Mercury 3 cyl Flywheel Timing Issue

Spin motor til #1 cyl is TDC , then make sure your flywheel, and dist. timing marks are correct according to manual. If at #1 TDC they don't line up you will know the flywheel has not been reassembled correctly. Also, high idle rpm's may be caused by floats not adjusted properly. These things are super finnicky and require very precise bend to ensure floats sit correctly, or stuck,clogged jets also.
I have the entire Mercury manual on my hard drive if you need any more specific info.
 

mnRIVERrat

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Re: 1972 65 hp Mercury 3 cyl Flywheel Timing Issue

Sorry orig post for 71 motor.

6-9 MODEL 650 1972 - 1975
Belt Timing
1- Remove the engine cowl. Observe
the straight line mark on the flywheel and
the plastic timing indica tor on the crankcase.
When the flywheel mark is aligned
with the plastic indicator, the No.1 cylinder
is at top dead center (TDC). Remove the
cap screw, washer and plate from the pulley.
Remove the belt. Remove the spark
plugs to relieve compression in the cylinders.
Rotate the flywheel until the timing
mark on the flywheel is aligned with the
plastic timing indicator on the crankcase.
Align the cast tab on the pulley with the
cast mark on the distributor adaptor. Install
the timing belt and cover plate. Install the
washer and cap screw to secure the plate.
Tighten the capscrew to a torque value of
60 in. Ibs (6.78Nm). Install the spark plugs
 

rdmotors

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Re: 1972 65 hp Mercury 3 cyl Flywheel Timing Issue

OK set the arrow to crank and we got high rpms again. Jumped the belt one tooth counter clock wise and the motor rpms got even higher. I thought I was retarding the timing but from the results dont know. Going to look into setting stock timing and then check floats....this thing sounds great and starts to good just got to be something little off. Will keep you posted I will get this thing today or tomorrow or the next day......or the next.......

Thanks for the info cant keep it straight in my mixed up mind.
 

rdmotors

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Re: 1972 65 hp Mercury 3 cyl Flywheel Timing Issue

Well got it.....Timed the flywheel to 23 degs at the pointer remember I am missing the pointer so guesstimated it. Removed the carbs and lowered the setting on closing the needle, now is set to around 15/32. Tried running it and still high revs...then I jumped the timing belt one cog ccw and........so run great....well stumbled alot. Set the idle screws to about 2 turns and she smoothed right out. Run at or around 800 to 1000 rpms. Got the carbs set, low idle screw set, timing screw set and I am done!!
Thanks for all the help
Now its time to go fishing!!!
 

sutor623

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Re: 1972 65 hp Mercury 3 cyl Flywheel Timing Issue

Did you run it on muffs or in a bucket? You may need to set the idle a smidge higher if you set the timing on muffs.
 
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