Timing and Sync of Merc Inlines (to 1988)

[redjmp]

Re: Timing and Sync of Merc Inlines (to 1988)

Great info!<br />I just want to verify this is the correct procedure with an '86 115.<br />The decal says 6*ATDC running and 18*BTDC at cranking speed (400 RPM) which is suppossed to equate to 21* @ 5500 rpm.<br />Now from what I understand, the first little bit of throttle arm travel only advances the spark and does not engage the carburetors' butterfly valve. Is this correct?<br />However on this motor, I need to back the low idle screw all the way out until the rod that connects to the armature under the flywheel (which is connected at the top end of the throttle arm) makes contact with the front cowling support bracket and can go no further but at this point I can only get 5* ATDC.Assuming this is close enough(I am only using cranking speed here)<br />Should I then adjust the caburetor cam to make contact at this point?<br />Doing so will mean that the carbs will start opening with any movement of the throttle and therefore idle rpm will not just be a function of spark advance.<br />Thanks for your valuable input Clams.

 

[Clams Canino]

Re: Timing and Sync of Merc Inlines (to 1988)

Yes the 1st little bit of movement just runs advance, unless of course the reeds are so tired that you need to be at 4 degrees before TDC just to idle it. <br /><br />Forget the decal... adjust the carb to arm adjustment so that the arrows on the swivel bracket line up just as the tang 1st contacts the carb bodies. Forget totally any ATDC numbers.<br /><br />Then set the screw so that you're about 4 degress BTDC at cranking when it makes contact, then do max advance etc etc.<br /><br />And you have it backwards, 21 at cranking = 18 at WOT. <br /><br />-W

 

[ayuh8]

Re: Timing and Sync of Merc Inlines (to 1988)

clams i left a question for you on the i boat forum...if ya get a chance..could you take alook..i keep blowin a fuse on the starboard side on my 115 tower thanks for the help

 

[Arty_G]

Re: Timing and Sync of Merc Inlines (to 1988)

^^<br />now just to find the same page for my 83 v150 v6

 

[redjmp]

Re: Timing and Sync of Merc Inlines (to 1988)

Clams, thanks again! Got this thing purring like a kitten set up just the way you said.
Just have a few more questions.
I don't understand what 6* ATDC on the sticker is there for if we should not use it?
Did mercury get this wrong?
The motor sure does not like to run when set accordingly.
Maybe there is some sort of convoluted way with which to use this spec?
Forgive me Clams but I gotta know why!!!
I went digging for info on the parts express pages, the carbs on this engine should come stock with 0.074" jets but mine had 0.076".I changed them back to save fuel.
This motor has gobs of power and an amazing holeshot on my 15" ski boat so I don't need so much power and I will not run it at WOT .Your thoughts?
Also, center carb had a white float and 1&3 had brown ones. Is there a difference?
One more thing, the 3 blade aluminum prop has no markings that can be seen while mounted. I want to find out the pitch. Do I need to remove it to find the info?
This boat just jumps on plane and boogies . It spins up to 5200 rpm @ 39 mph (gps) . It definately appears to be lower and slower than perhaps it should be.
It is on a 600lb 15 footer shallow vee..
All of these numbers are just marginally better than what it did while mounted on a much heavier and bigger deep vee whith several coats of chipped bottom paint.
I don't think it is over propped because it does not labor at all getting out of the hole.
It would hit top speed in just a few seconds on either boat.
Any thoughts?
Oh one other thing, seems my plugs get fouled easily especially while idling for extended periods.
I had the same problem with my '65 650 ( didn't make them with thermostats and would run cool at idle) fouling the buhw or w2's. ( surface gap)
Finally put in a set of j8c's (hotter) and never looked back !!! ( nice golden color).
Is there a certain conventional plug that I can use on this motor like mabe a j4c
Thanks again!

 

[Clams Canino]

Re: Timing and Sync of Merc Inlines (to 1988)

The waterpump can push water in either direction, it forces water from the big end of the oval to the smal end, it does not know what direction it's turning in, nor does it matter in those pumps.

-W (bumping the thread)

 

[redjmp]

Re: Timing and Sync of Merc Inlines (to 1988)

!?!?
Perhaps this reply is intended for another thread?

 

[casi77]

Re: Timing and Sync of Merc Inlines (to 1988)

Im a newbie on this timing procedure.. had a few questions..

what is or where is this "tang or trigger" screw? Anyone have pictures for this? Or more pictures of everything discussed here?? anyone nice enough to post these up pleasee for us newbie's out here.

im confused also with the direct charge and vanilla crossflow.. what would mine be, its a 71model merc 65hp, 4 cyclinder? degree measurements...

thank youu..

Manual specs are different for each but this is close enough to get them all REAL close. This assumes nothing is broken or "wrong" with it. This also assumes that the timing pointer is properly adjusted (if adjustable) to accurately read TDC of the #1 piston.<br /><br />This basic procedure will work for all the 2/3/4/6 cylinder inlines from 1960 to 1988. It's not for the newer 3 and 4 cylinder loopers.<br /><br />Engine off<br /><br />Disconnect throttle cable<br /><br />Pull throttle arm to full throttle and verify carbs open fully. Adjust main throttle stop so that the carbs are JUST hitting thier own little throttle stops. The idea here is that you want the screw stop and NOT the carbs acting as the "final stop" for your throttle lever.<br /><br />Return the throttle to idle, carbs should be closed. Set all idle screws to 1 3/4 turns out from lightly seated.<br /><br />Remove all plugs except #1, hook a timing light to #1. Then follow the narritive.<br /><br />When the throttle is in the idle position the carbs should be fully closed and the ignition retarded. It is the amount of retardation that determines your idle speed and is set later with the idle stop screw. <br /><br />Timing Event One - throttle pickup.<br />As the throttle is advanced, the spark timing advances toward TDC and then to before TDC. As the timing is just passing TDC the 1st (minor)throttle pickup should hit and start to open the carbs. Use the timing light. Adjust the tang or trigger screw to make this a reality. All of them are speced different, but if the 1st pickup hits at 3-4 degrees BTDC advance - you win. Use the timing light with a friend cranking it to complete this setting.<br /><br />Timing Event Two - max advance.<br />As you continue to advance the throttle the timing will advance while the carbs slowly open a bit more. The next adjustment is max advance, this is the point where the distibutor (or trigger) can advance no more. Set the max-advance stop to 21 degrees for "direct charge" crossflow inlines and 34 degrees for the older plain vanilla crossflows. Use the light, - err to the side of caution.<br /><br />Right after max advance, further throttle motion should cause the second throttle pickup to hit and open the carbs to full. You already set that -now verify it.<br /><br />Leave the throttle cable disconnected and go to the water. Leave the boat strapped to the trailer and back it in so it's deep enought to run. Have a friend crank it while you operate the choke and throttle. Warm it up at 1500 rpms's.<br /><br />When "warm" adjust the idle stop screw for about 800 rpm and then ajust your idle needle(s) in (one at a time) till the motor stumbles. Quickly backing it out 1/2 turn from "stumble" will usually save it from needing a re-start. Do that for all the idle screws. Re-set idle stop for 800.<br /><br />Now have your friend put it in gear (make SURE you are on the transom NOT in the water) and reset your idle stop for as low as you can get it. 500-600rpm is great if your old reeds will let it idle that low in gear. Now, re-adjust the idle screws, in to stumble, then 1/2 turn out. When you've gone back and forth with that a few times and have it "perfect" - adjust each one out 1/4 turn.<br /><br />Reset the idle stop so that it's about 700-800 out of gear and 500-600 in gear. Sometimes bad reeds won't let you get that low, you've GOT to get it under 1000 in neutral (worst case) to avoid beating up your lower unit when you shift into gear, even 1000 is "bad" but like I said "worst case".<br /><br />Now adjust (and hook up)the throttle cable so that with the shifter in neutral, there is light to moderate pressure holding the throttle arm against the idle stop.<br /><br />Take the boat off the trailer and go out in the water. Try the hole shot. If it falls on it's face try adjusting the idle screws out 1/4 turn at a time (all of them together) till you can get a hole shot. You can kind of do this on the trailer at the ramp, but it's not really safe for you, the boat, or the tow vehicle.<br /><br />You're done.<br /><br />-W

 

[meddo]

Re: Timing and Sync of Merc Inlines (to 1988)

^ ^ ^ ^

Lets get this back up to page one where it belongs.

 

[SpinnerBait_Nut]

Re: Timing and Sync of Merc Inlines (to 1988)

I thought this was in the FAQ's already.
I will put a copy of it there now though.

 

[Clams Canino]

Re: Timing and Sync of Merc Inlines (to 1988)

I've been trying to get it into the FAQ's for over a year. We've sacrificed many live chickens to the Cods here.

Our prayers are now answered??

-W

 

[tashasdaddy]

Re: Timing and Sync of Merc Inlines (to 1988)

i thought this was in the new engine faq but then it disappeared., have saved it and email it around to those who need it. don't know how to link, paste and all that computer stuff.

 

[urbanp]

Re: Timing and Sync of Merc Inlines (to 1988)

This is great info.
Thanks for the post.
I am going to set the timing on my 1976 1500, but I'm not quite sure what: direct charge" crossflow inlines and plain crossflow lines are.

Could someone please explain.

 

[Caddy_Kid]

Re: Timing and Sync of Merc Inlines (to 1988)

While chasing a top end problem (see what I have done so far here: http://www.iboats.com/bbboard/bbBoard.cgi?a=viewthread;fid=29;gtid=932994), I figured I would check timing and such on my 1965 Merc Mark 1000 dual coil ignition. I found the timing mark on the flywheel, and after removing the cover on the distributer gear, found the little arrow. The two line up when they should, which is good. But now I see that there are no degree marks anywhere. Not even sure what the mark that it has is actually reading. No pointer either.

In reading my factory manual, it seems as though I need special tool ("timing gauge") to measure .222 BTDC on piston #3, rock back and forth, push this, etc. I dont have these tools, and my local shop wont touch "something that old", even if they did still have the knowlege/tools. Is there an easier way? I have digital calipers, but I'm not sure where the measurments are to and from. Thanks.

 

[Caddy_Kid]

Re: Timing and Sync of Merc Inlines (to 1988)

accidental double post

 

[Clams Canino]

Re: Timing and Sync of Merc Inlines (to 1988)

To find TDC all you need is something to measure piston deflection being the same off TDC and then TDC is in the middle. Even if you stick a pencil eraser in the hole and rock it back and forth till you "feel" what TDC outta be and mark it in pencil against a known reference point. Do this 10 times and the average will be darn close to true TDC. Then mark that in white. Next count the teeth on the flywheel and and remembering that a flywheel is 360 degrees around... do some math to get the value of a tooth and a 1/2 tooth..... etc... from there you have enough references to get it REAL close.

In the case of yours, set one set of points for 90 degrees dwell (open) and then set the second set to open EXACTLY 60 degrees after the 1st set. Then set max advance to 34 - 35 degrees etc etc...

It's a pain, but I did it to a '61 Merc 800 several years ago and got it dead nuts on.

-W

 

[Caddy_Kid]

Re: Timing and Sync of Merc Inlines (to 1988)

Never thought about counting the teeth for reference points, good call. Seems as though they could have made it allot easier.

I do have a dwell meter, but have yet to check it. Not even sure if it will work with two sets of points. I have never taken the distributer cap off of one of these dual points setups, so we'll see how it goes. What should be replaced in one of these things, condensor, coils, points etc? Its acting like either the electrical or the timing is changing while running at different RPM's. Thanks.

 

[merc850xs]

Re: Timing and Sync of Merc Inlines (to 1988)

Hi,

I would like to check that the '77 Merc 850XS 4cyl I have is tuned ok. I have inductive timing light, dial indicator etc.

If someone could answer some or all of the following it would be most appreciated.

Says on motor timing is 27 degrees or 0.172 BTDC.

Is the last figure above thousandths of an inch?

Is my motor direct charge crossflow 21 degrees, or the older plain vanilla crossflow 34 degrees?

Should I use one of the above figures or the 27 degrees as stated on motor?

How is the measurement .172 used? Maybe it isn't?

I have timed a rotax points 503 50hp twin (ultralight motor). They have no advance of any kind, timed static @ .086th BTDC, done with a buzz box and must be done accurately.

Hope thats not to many questions.

Thanks for all the help.

Dave

 

[Clams Canino]

Re: Timing and Sync of Merc Inlines (to 1988)

Wow............. "The Night of the Living Thread"!

.172 is not used. Yours is direct charge, just make sure your TDC pointer is correct and then time it for 21 degrees.

-W

 

[anthony115merc]

Re: Timing and Sync of Merc Inlines (to 1988)

on one of my motors the throttle arm is real easy to move and on the other really hard what is with this?btw 115 inline 6 mercs