Flywheel ????

Are the flywheel key and the sheering pin the same thing? and If so, if it has been broken wouldn't there be some noticeable play between the flywheel and the piston movement?

Re: Flywheel ????

What engine are we talking about here?

Re: Flywheel ????

OOOp's - 1975 Mercury 650 65 horse 3cylinder

Re: Flywheel ????

Not that you would notice by just turning the flywheel by hand. The flywheel key can only be inspected by removing the flywheel. Remember, this was just a suggestion. Maybe others will have more ideas on your problem. It could also be a broken reed causing the backfire....<br /><br />BTW for the rest of you, this goes along with this previous post:<br /><br /> All I Hear Is A CLICK

Re: Flywheel ????

Man that is just what I don't want to have to do!!!!!!!!!!!!!! Also it only backfired twice when I first started trying to crank it after doing all the other repairs to it first. But after several other tries it has since stopped the backfiring and turns over smoothly, just doesn't crank. I'm just trying to eliminate this as a pontential problem is all (the flywheel key broken that is).

Re: Flywheel ????

Hold off for others to take a shot at it first..

Re: Flywheel ????

Sorry, WhoohooIt'saBoat, but RB is correct. To inspect the flywheel key, you must remove the flywheel. <br /><br />I would suspect though, that there is something else going on with the motor if you can move the flywheel alot without moving the pistons. Of course where the piston is in the stroke can also make a difference. If the piston is at the very top or very bottom of the stroke, you need a dial indicator to see movement in the piston as the flywheel is rotated. Is the engine noisy? Is the compression low? <br /><br />et us know!<br />Good Luck!

Re: Flywheel ????

I can't detect any play, as far as i can tell there is no play. The compression is good on all three and the motor is not noisy when turned over. I seriously think the reason it isn't cranking now is because the switchbox is probably bad. I'm imbarrassed to say this motor has been sitten hmm, hmm, layen up a freeeekin long time before it was given to me. But the compression was good , no bearing play, and the lower unit only needed an impeller and gear oil changed. So, me in all my wisdom thought that it would be repairable, so i went to work on it.

Re: Flywheel ????

. But after several other tries it has since stopped the backfiring and turns over smoothly, just doesn't crank.

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I think you mean it "Just doesn't start". Do you have spark to the plugs now? And it sounds like the pistons ARE moving, when you turn the flywheel by hand. A compressiom test will verify if the pistons and rings are good.

Re: Flywheel ????

That is one of the other tests I want to do but It is raining today.

Re: Flywheel ????

hello<br /> if your going to play with outboards your going to have to buy the correct merc manual. in the manual is a section on how the ign system works. I think your flywheel is splined not keyed. a quick test is to insert a 6" phillips screwdriver in #1 cyl and rotate the flywheel slowly in a clockwise rotation to the point the screwdriver comes all the way up and stats back down, then rock the flywheel back and forth to set the piston at TDC you may be off a degrre or 2 but now look at the TDC mark on the flywhee3l in relation to the pointer. if its within a few degrees plus or minus your key is fine. its a quick check that can be done in less than 3 min. somewhere one of the guys posted how to make a spark tester. find it and make one.<br /> if it sat that long rebuild the fuel pump and carbs and install a new water pump kit.<br /> good luck and test compression and spark then go after fuel. switch boxes are expensive.

Re: Flywheel ????

why does everyone assume that I don't have the manual? That's how I learned how to do the carb rebuild (although I had to go ask the marine repairman some things do to the manual not covering real world needs), the water pump impeller change, gear oil change and test, fuel pump rebuild and all fuel lines changed do to age. The manual is what got me concerned about the stupid rectifier. The manual does not say anything about the key although it does state it has a key, but not one thing about them being broke, or to even check for it. I do appreciate you telling me how to do the TDC Rodbolt as the manual mentioned very little about that procedure and then only to aline the distributor timing with the cylinders. But what you said makes alot o-sense, if the flywheel mark is close/dead-on to the plastic pointer when the 1 cylinder is TDC then that would a very good test to make sure the key is not stripped/sheered thus moving me on to something else to worry about. These manuals suck, they rarely cover my real world needs. You guys ROCK!!! You've been better to/for me than any manual. Thanks. The reason I said switchbox is because "the manual" gives the idea that the switchbox can prevent the ignition system from functioning. Please someone correct me here (Clams???) Thanks again.

Re: Flywheel ????

Originally posted by WhoohooIt'saBoat:<br />[QB]why does everyone assume that I don't have the manual? <br /><br />Because some of your questions defy logic. <br /><br />Now seriously... take one thing at a time. <br /><br />Get the starter fixed, then pump up the ball, choke it, and see what it does under a "normal" starting attempt. If it has a distributor, make sure the cap is all clean and dry inside and that the spring loaded carbon button is good.<br /><br />A broken flywheel key is rare, it's not like a lawnmower.<br /><br />-W

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Re: Flywheel ????

It doesn't sound like you've had the flywheel off in your recent service work. If you haven't(and can't get it off) don't worry about the key being sheared. BTW, does this one have splines?

Re: Flywheel ????

well according to the "manual" it has a key. And yes I have not had the flywheel off. I am just trying to eliminate possible problems one at a time. Can't do much today again due to rain. Thanks all.<br /><br />BTW Clams I replaced the distributor cap, plugs and all the plug/high tension wires after redoing the water pump and fuel systems before attempting to crank the motor to eliminate these as possible problems.

Re: Flywheel ????

Originally posted by WhoohooIt'saBoat:<br />BTW Clams I replaced the distributor cap, plugs and all the plug/high tension wires after redoing the water pump and fuel systems before attempting to crank the motor to eliminate these as possible problems.

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Overkill $$. Usually a good cleaning is all it takes, unless a wire is frayed / broken or the cap is cracked.<br /><br />-W

Re: Flywheel ????

it might be overkill. But this motor has been sitten/layin for 15yrs.

Re: Flywheel ????

Reason I say it, is those are solid (wire) core wires, permagap plugs, and the caps are priced through the roof and can usually be rehabilitated with a trip through the dishwasher and a new carbon button.<br /><br />It's not like car stuff, I wanna see something *broken* before I let Mercury bend me over the transom. <br /><br />-W