merc 800 timing mark question

[Yachtzee]

I have a 1971 merc 800. I need help with making sure the timing marks are right. My flywheel has a single row of three dots and a white dot painted on the top above them.

When the #1 cyl is at TDC the timing marks on the flywheel should point at the #1 TDC mark on the cowl decal correct?


The timing belt should be set so that the arrow on the distributor pulley points directly at the three dots on the flywheel is that correct?

I also have a dot stamped into the rim of the dist pulley opposite the arrow and the pulley has a little bump on its lower rim that woudl ssem to line up with a little bump on the casting at some point, what are these marks used for?

I an not get this 800 to even cough and it is driving me nuts. I am humbled as I have never not been able to get something to start.

 

[Laddies]

Re: merc 800 timing mark question

If you first used something in the cyl to see that the flywheel is index to the crank right then you have described the process of installing the belt and alinging the belt properly. If the engine does not even fire or pop have checked for spark at the plugs? It should at least backfire.

 

[Yachtzee]

Re: merc 800 timing mark question

Laddies, Thanks for the reply. I do not have a dial indicator so I put a screwdriver on the piston crown on #1 and turned the flywheel till I found that little flat spot, you know what I mean? The flywheel on this one is splined but it looks like it would be hard to put it on wrong. Of course, that does not mean that someone before me did not pull the flywheel off the hub and put it back wrong. I have pulled plug # one and slowly hand cranked with the key on and watched it spark as the the # 1 piston approaches TDC. I have a hot blue spark on all four and the cranking speed is good. I do not even get a pop out of it. I have tried spraying premix into both carb throats, and even tried pulling the plugs and spraying gas in, not even a pop. I am going to pull the front shroud support off next so I can get a really good idea if it is pulling a vacuum in through the carbs when cranking. I do not know why it would not. I replaced top and bottom crank seals The big O rings and sealed the case halves, The reeds look ok. a tiny bit of daylight on a few maybe but none bent or broken. this is driving me nuts

 

[jerbear56]

Re: merc 800 timing mark question

I read your previous post. The flywheel with the dots and the straight line was only used up to a certain serial number, then only the three dot flywheel was used afterwards. From what I read, it sounds like your distributor is timed correctly.

It's very possible that the firing order was changed also.

Try reposting for info on the firing order for the merc 800 with the lightning ignition and see if the reply matches the firing order you are using. And good luck!

 

[Laddies]

Re: merc 800 timing mark question

Yahtzee, if you used the screwdriver to make sure #1 was at TDC and the mark was on the 0 then the flywheel is indexed properly. Sometimes someone will take the bolts out of the hub and not align the flywheel with the mark when reassembling. Did the engine run before and why was it torn down?

 

[Yachtzee]

Re: merc 800 timing mark question

Thanks for the responses.
Laddies, I bought the motor for $200. When we picked it up we did a quick compression check, the readings were high, like 150# each (carbon build up?)

Owner said motor would not run. On the stand we squirted a bit of fuel into one carb throat and it fired for a second

Got it home, put on muffs and hooked up the tank, it would not even pop. Pulled the carbs and they were a total disaster, gummed up main jets, no way it would run like that. Put rebuild kits in both carbs. got it to start, but it would not run right. Only would run wide open would not idle and could not keep it running. Previous owner hinted at something like "bad ceramic disk in side'? I have no clue as to what he meant. Maybe he meant he thought the reeds were bad? But the way it ran I was willing to bet crank seals or the like, or maybe a bad reed. The bottom seals were not great and the o ring on the bottom bearing cap was in fact broken in two places. I though that I found the cause. So I tore it down and resealed and patched up the ususal crumbling wiring. Now nothing, won't even cough. But I have a spark on all four, Electronics is supposed to be my expertise but no one is perfiect, if I had a wiring error would I get a spark at all? I have another control box, and two other ignitions I could try, a mageneto and a lightining energizer distributor.
Thanks for any and all insights

 

[Laddies]

Re: merc 800 timing mark question

It's wired right or you would not have fire, are you using battery powered CD or lighting energizer, I tend to wonder if the spark is timed right but your explanation of the timing process is right. When you used the light to set the timing then you proved at lest #1 is in time however so if the firing order of the plug wires is right the engine should run when you squirt it with fuel. Then that leaves harder problems as you know from splitting the crankcase there is no ceramic disc, that leaves reed valve cocked or chipped, labyrinth seals damaged from a bad main bearing at sometime, massive air leak or the fellow you purchased it from induced the high compression by loading the cyls. with some type of lubricant. None of this I'm sure you want to hear.

 

[Yachtzee]

Re: merc 800 timing mark question

Laddies and Jerbear,
Thanks for your input. You made me confident that it was not an ignition issue. I wanted to see how the thing was sucking in the air fuel mix, so I took off the front shroud support and put my hand over the top carb while cranking, instant vroom vroom??? If you read any of the other posts I left on this motor you may remember that I thought it might have had a little fire and that the plastic drip tray under the carbs was melted. Well it looks like the choke plates got hot too and warped so that there was significant gap on the bottom edge. If I push the choke plates flat against the carb, it will :redfacenes.
I do remember that the manual said that these need to seal very firmly, I should have given them a better look when I rebuilt the carbs. I wonder how long the previous owner fought the issue? The inside of this thing looks brand new, the machine marks are still on the pistons and there is absolutely no scuffing on them and the bearing s all look new. It seems to run fine now at least on the muffs. I am still humbled that I did all the other work and it was that simple. These direct charge motors must really need to be choked hard to start cold.

 

[Moody Blue]

Re: merc 800 timing mark question

Thanks for posting back with your findings. Will take a hard look at mine this winter when I do the carbs. Have been having a hard start when cold issue. Cranks for about 15-20 seconds before it fires. Once warmed up, all I have to do is touch the key and it fires instantly.