Vintage Merc 50Hp, 8 Flywheel/ringgear bolts removed, how to re-time flywheel to hub, so distributor belt can be installed.

[Hitek Rednek]

Need to dive into the knowledgeable folk here for some info on this. Vintage Mercury 50Hp 500. Vin tag gone, any numbers I've found on the motor don't pull up in a vin lookup either. Has electric and recoil start. Customer attempted to replace their distributor timing belt themselves and gave up and now it's here in pieces. The 8 bolts were removed from the flywheel to the hub, so I'm starting from scratch here getting everything timed back up and then new belt installed and timed. Can't seem to find any previous forums or videos that match exactly what we're working on here. Besides the bunch of random paint marks and sharpie marks all over the flywheel from previous users, i have narrowed down what looks like 3 manufacturer marks, 2 of which are most likely the timing marks, i labeled the two that are stamped on the side "1" and "2 in the pictures, question mark is the one on the underside. From what I've come across throughout other videos and forums to similar newer models, looks like with the #1 piston at TDC, the 2nd mark on the flywheels out there that have two marks, (I'm seeing write ups with flywheels that only have 1 mark as well) lines up with the distributor gear arrow, and the #1 mark is lined up with the TDC mark on their sticker/pointer on the front plate of the motor. However i don't have any tdc sticker or pointer and the plate molding where that sticker normally would be is different then what I've been seeing. Im assuming this engine is the one that needs the base and advance timing set based off of piston position, and not with a light and timing marks. So with the #1 piston at tdc, and the flywheel hub sitting on the crank on the keyway, and then setting the flywheel on the hub and spinning it until the bolts line up in the 8 different positions, i can at one point, end up with the #2 mark aligning with the distributor gear arrow, and the #1 mark sitting in about the same spot as what im seeing on models that have the molding with the timing sticker. Now is that the proper way to re-time the flywheel to the hub to reinstall the 8 bolts? The more i read, the rabbit hole is getting deep fast with procedures for flywheels with one timing mark and others with two, and all the ones with two marks im seeing are for the motors that have the tdc reference sticker on the front of the motor, but we don't have that. There arn't any rust spots or scribe marks anywhere matching the flywheel hub to the flywheel at all to use as a reference point, and I'm not trusting all the random sharpie marks and paint marks that are all over the flywheel. (Which i removed before taking photo's)

So essentially, I need to know how to re-time the flywheel to the hub in the correct spot so the 8 bolts can be reinstalled and loctited/staked, with a note scribed in there to never ever touch again in case this ends up somewhere else, and then the actual procedure for that motor, to properly time the flywheel and distributor together for belt install, whether its with the #1 or #2 mark, or maybe even that other mark underneath, and then if its supposed to be at TDC or a different flywheel position. I know there's gotta be 1 or 2 individuals in here that know what I've got on my hands here. Please help! Thank you.

 

[Chris1956]

Putting the flex plate on correctly is easy. Eight bolts means 360*/8 = 45* per hole. It should be easy to get the timing within 45*. so set the top piston to top dead center with a screwdriver.

Now install the timing belt on the inner flywheel and put the flexplate on and turn it until it shows TDC on the timing mark or pointer. Turn it until the nearest holes align with the inner flywheel. Install the 8 bolts with some blue locktite.

There is a cast arrow on the distributor pulley. With the flywheel assembled correctly and the #1 piston at TDC, the cast arrow should point at the punch mark on the flexplate, when timed correctly. Install the belt at that alignment. Install the pulley cover with some blue locktite.

I recommend you get a service manual, as it sounds like you may need it.

 

[Hitek Rednek]

Putting the flex plate on correctly is easy. Eight bolts means 360*/8 = 45* per hole. It should be easy to get the timing within 45*. so set the top piston to top dead center with a screwdriver.

Now install the timing belt on the inner flywheel and put the flexplate on and turn it until it shows TDC on the timing mark or pointer. Turn it until the nearest holes align with the inner flywheel. Install the 8 bolts with some blue locktite.

There is a cast arrow on the distributor pulley. With the flywheel assembled correctly and the #1 piston at TDC, the cast arrow should point at the punch mark on the flexplate, when timed correctly. Install the belt at that alignment. Install the pulley cover with some blue locktite.

I recommend you get a service manual, as it sounds like you may need it.

A manual was dropped off with the engine, however doesn't cover anything to do with the 8 bolts since they're not supposed to be removed, and im not even 100% sure it's the correct manual since I can't fully verify the model of engine. I don't think you read my write up fully. There is no timing mark or pointer to align the flywheel with, see in my pictures. And my flywheel has 3 potential timing marks on it, most likely are the two that are straight lines punched on the side. And yes I already have the cast arrow on the distributor lined up, as shown in the pictures, but still dealing with what mark to even align it with on the flywheel, depending on where the flywheel is supposed to bolted down.

 

[Hitek Rednek]

The 1965 and prior manual does state for one of the 500 models, there's two markings, one should have a "0" marked above the one mark, and it indicates .235" BTDC, and the other is for TDC when aligned with the arrow on the magneto pulley. I don't see any "0" marking near any of my timing marks either, nor do the pictures match, however its closer than what the 1965-1989 manual shows. I can try some piston measurements and see if any of the marks on the flywheel work out to TDC and .235" BTDC and possibly work backwards from there.

 

[Chris1956]

Gee, getting the flex plate back on properly is child's play, if you have a timing mark for TDC. I do not agree that those 8 bolts are never to be removed. It is a lot easier to remove those and pull the stator, then to pull the flywheel bolt.

You really need to know the year of the motor so you can get the correct timing sequence. Look on the block, near the transfer covers for a block part number. You may be able to find the parts list on the crowleymarine site using the block part number. That will tell you the year. Now you can use the correct service manual to time it.

 

[Chris1956]

FWIW, I think the year of your motor will be late 60s or early 70's. My '73 Merc had timing marks on the cowling, and the timing decal on the flexplate. My '77 had a timing pointer and timing decal on the flexplate. Your flexplate looks like it has a single timing mark, likely TDC. It therefore looks pre-1973.

 

[jimmbo]

The cowl and face plate place it in the 74-75 era

 

[Hitek Rednek]

FWIW, I think the year of your motor will be late 60s or early 70's. My '73 Merc had timing marks on the cowling, and the timing decal on the flexplate. My '77 had a timing pointer and timing decal on the flexplate. Your flexplate looks like it has a single timing mark, likely TDC. It therefore looks pre-1973.

I do agree that putting the flexplate back on would be childs play-with a newer style motor like what you had, with one timing mark on the flywheel and/or sticker, and then a timing pointer or sticker on the engine cover, of course it would be easy then, but this is indeed older then that. That is a good tip however to use the block part number to narrow down the year. I'll see if Merc has any more model specifc manuals. The two i have from merc currently are a 1965 and prior outboard, and 1965-1989 outboard, actual Merc manuals, not third party. Maybe my pictures are confusing, i have 3 separate pictures of 3 separate marks, there is one on the underside of the flexplate but just above the ring gear teeth, probably can't even see it once its installed on the engine so im doubting its used for anything, then two more perfectly straight up and down marks on the outter edge of the flexplate, about 60 degrees from one another, labeled 1 and 2 in my other picture. I'll see where the block part number brings us for a closer year, thanks.

 

[Hitek Rednek]

The cowl and face plate place it in the 74-75 era

Good info, will look closer at that, thank you!

 

[racerone]

I see rust / stain marks on the bolt circle.----Enuff to put it back on the way it was.---I do that when i get one of these worked on by some club fisted individual who took flywheel off the hard way.

 

[Hitek Rednek]

Found an older forum post of a vin stamp possibly being on the crankcase distributor bracket, if that's correct then we do have this number, which according to the chart puts it as a 1965.. But i see what jimmbo is saying, those colors match the 1975 era.. Sooo has someone stuffed a different cowl and faceplate on there at some point in its life, or is that not a true vin stamp on that crankcase bracket? Also according to the engine block part number of 831-2500, that closely matches the parts diagrams from the 1965-1967 parts book. Also a matching part number on the exhaust cover from the 65-67 book, chances are this is a 1965.

 

[racerone]

Post some pictures of the magneto / distributor.---The ignition coil if it is visible.

 

[Hitek Rednek]

No coil pics sorry.

 

[Hitek Rednek]

Going off of the #1 and #2 marks only, the only one that lines up with the bolt holes and with the arrow on the distributor while the #1 piston is at TDC, is the #2 mark. I checked betweeen all 3 marks to see if either made a difference of .235" in piston position and they do not, so i think can disregard that procedure in the manual, must be for an older 500.
Specifically for the 1965 it says there should only be one mark, perhaps someones punched another mark in there while doing their own timing, it sure is nice and straight like the other, they look identical, but doesn't align with the distributor at all, nor is anywhere close to .235" BTDC. We'll probably just assemble it based off that #2 mark next week and see where that gets us.