Merc 40HP ??

A friend has what appears to be a 40HP Merc. The transom mount serial number is 5484299. I think it's either a 1978 or 1979. I found a number on the block (between the cylinders-starboard side) that doesn't appear to be a casting number, the number is 5 18 9...I'll guess it's the date code of May 18, 1979. Can anyone confirm this? He bought a service manual from a local dealer, he gave the counter man the 5484299 serial. The manual covers '75 through '78. The problem is,the pics and destructions for doing the sync and link don't jive with his motor. I did find the info for the timing on a sticker that says 79 40. Having no history on this motor, I'm not sure if the powerhead was replaced etc. If this turns out to be a '79 40hp, the dealer sold him the wrong manual based on the 5484299 serial.

Can someone enlighten this Jhonny-Rude guy with the Merc numbering system?? Thanks in advance.:redface:

Re: Merc 40HP ??

Based on the serial number, that is a 1979 2cyl Merc 40hp



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Re: Merc 40HP ??

Thanks for the confirmation.

Re: Merc 40HP ??

Update:

My friend returned the OEM manual (didn't cover his model year motor) and they sold him a Clymers (yea, don't say it, I know). Anyway, I made an observation with BOTH manuals....When setting the timing, they mention looking through a small window to align marks on the flywheel. The problem is, there is no window on his motor. The pictures-illustrations don't match his motor. His motor has a pointer.

I'm posting 2 pics in hope that someone can sort this out. I hoping to identify this motor and perhaps I can find the timing, max advance settings etc.

Again, thanks in advance for any help.

Re: Merc 40HP ??

Where is the recoil starter bracket? There's supposed to be a cowl (held by three bolts) and then a recoil starter bracket that fits over the flywheel. It has two holes that slide over those two black posts you've got on either side of the switchbox.

If your motor is a 402 like mine ('74), the timing window is on the recoil starter bracket arm about 10 degrees away from that pointer thingy...

Re: Merc 40HP ??

As you can see, this one doesn't have a recoil starter, it's electric start, no tiller. Both the OEM and Clymers says to set initial timing to the 2-dot mark on the flywheel. I'm not sure this flywheel has a 2-dot mark. I did see degree marks for BTDC and ATDC . What is the setting, in degrees for this 2-dot mark? I guess I'd also need the degrees for the "solid line on the flywheel" (max timing advance) too.

As an aside, I didn't see where a rope start handle would be fitted through the cover anyway. I find it strange that there's no mention in both manuals for setting a motor with this pointer-flywheel setup.

Re: Merc 40HP ??

Bump...

Merc 40HP ??

Xcusme
I have the same 79 merc motor as you(or your friend) and was wondering how that motor runs?

I have had it for a little over a year now. Since I got my motor I have changed out the starter, impeller, switchbox, stator, rectifier, gas lines from tank to motor, and rebuilt the carb. Most parts mentioned were switched out because they were in need except for the gas lines and switchbox, although I am more comfortable with having the new switchbox on now(same CDI switchbox replaced as the on pictured in your motor).

My motor runs much better now, although I am still trying to diagnose my idle problem. It is very close to being where it needs to be but I can't quite find out what is causing it to stall sometimes at idle and at it's lowest speed. I have set the idle to where I don't think I can get it any better, checked for leaks or holes in lines, compression is good, good spark, mixture is good.
I just can't get it to where she purs at idle consistantly. Although, sometimes after running it up or down the river quick then when I go to put it in neutral it will idle strong. But lets say I am trolling for a good half hour straight and I go to pt it in neutral she will kill. I can't seem to get the idle set to where it will idle just a little faster to stay running all the time without givin it just a tap extra throttle.

Was curious if you or your friend has had the same experince or are currently experiencing the same problem with this particular motor.

Anyone else familiar with the same motor have any suggestion?

Merc 40HP ??

Xcusme
I have the same 79 merc motor as you(or your friend) and was wondering how that motor runs?

I have had it for a little over a year now. Since I got my motor I have changed out the starter, impeller, switchbox, stator, rectifier, gas lines from tank to motor, and rebuilt the carbs. Most parts mentioned were switched out because they were in need except for the gas lines and switchbox, although I am more comfortable with having the new switchbox on now(same CDI switchbox replaced as the on pictured in your motor).

My motor runs much better now, although I am still trying to diagnose my idle problem. It is very close to being where it needs to be but I can't quite find out what is causing it to stall sometimes at idle and at it's lowest speed. I have set the idle to where I don't think I can get it any better, checked for leaks or holes in lines, compression is good, good spark, mixture is good.
I just can't get it to where she purs at idle consistantly. Although, sometimes after running it up or down the river quick then when I go to put it in neutral it will idle strong. But lets say I am trolling for a good half hour straight and I go to pt it in neutral she will kill. I can't seem to get the idle set to where it will idle just a little faster to stay running all the time without givin it just a tap extra throttle.

Was curious if you or your friend has had the same experince or are currently experiencing the same problem with this particular motor.

Anyone else familiar with the same motor have any suggestion?

Re: Merc 40HP ??

Xcuseme,

The doubledot is supposed to be 7degs BTDC and the solid line at 27 degs BTDC. However, I'd check for TDC first, as my flywheel was off by one bolt (approx 45 degs) by whoever owned my motor previously. Also, because of the poorer quality gas today compared with 1970, retard your max advance to about 21 degrees. I wouldn't run it higher than that...

Looks like the pointer on your motor is about 10 degs away from the timing window on mine. Wondering if a previous owner converted your motor from a recoil to electric, changing the flywheel and throwing away the old recoil bracket. Probably fab installed that pointer, too. Guessing here...

Basically, I'd start from scratch, put a straw in the #1 spark hole and rotate the flywheel until the straw is pushed all the way out. Mark that with chalk as TDC and make some new marks. On my motor, there's about 20 teeth every 90 degrees, so my doubledot is about 1.5 teeth away from TDC and the solid line is six teeth away from TDC. This is moving clockwise around the wheel from TDC.

Kellyisu,

I had this exact problem with my motor earlier this year. Basically, I went through the entire link'n'sync from the FAQ and the problem cleared up. My guess is that the throttle linkage is probably about one turnbuckle twist too loose, but I'd do the whole thing just to make sure all is tight. Special care should be taken while resetting the carb low idle screw, both in idle and in gear. Also, remember at the end to set the throttle linkage to where it is holding with some pressure against the idle stop screw. That _should_ help your inconsistent idle problem. For reference, my 1974 402 idles about 850 rpm out of gear and right at 650 in gear...

Re: Merc 40HP ??

Kellyisu,

The 40hp came with a boat my friend bought. He took it to a guy who claims to have statically timed the motor. Friend said he couldn't get over 4,000 rpm's at WOT. He then started futzing with the adjustments without a clue of what did what. He claimes the motor ran well at idle, but wouldn't idle lower than 800 rpm's. Now that I have a manual and the timing figures, I'll give him a hand at getting things back in order. I asked friend to get some compression figures, 135 top, 130 bottom, so he's good so far. He said he installed a carb kit, but had no experience in rebuilding carbs, so i'll check that as well.

I'm sure his 'adjustments' are pretty much way off, but I'll soon set things right. I'll report back on the final results.

Garndawg,

Thanks so much for the info, specs, and suggestion for TDC. You're probably not too far off about the mods that may have been done.

Re: Merc 40HP ??

Thanks Garndawg-
I have thought that as well and have been wanting to do that. I just havn't yet because I don't know exactly how to do it. I'm sure it is easy. I don't have a manual but I do have the seloc online subscription( I just bought this last year because I needed to fix something ASAP and it was the fastest thing closest to getting a manual that day) that has helped me fix all of my other problems. Although, I have not been able to find anything on there that shows me how to adjust the link n' sink or I would have done that by now.

Is there any chance you have access to a camera to take a picture of what I am looking to adjust on the throttle linkage. I don't hav a digital camera or I would do so myself.

Or if you had a easy way of explaining what it is that I am looking for to adjust I could try, anything would help. I have been trying to find info on this with no success.

Thanks


Excusme-
Keep me updated on how things go with that motor, I am curious.
Thanks

Re: Merc 40HP ??

Excusme,

On that 4000 rpm problem, was that with a calibrated tach, or just the one in the boat? If he was reading that off the boat console tach, check the back of that instrument to make sure it's set for a 2 cylinder motor. Mine was previously set for 3 cylinders and read 4000 rpm until I reset the selector on the back of the tach.

Kelly,

I'll try to do that sometime this week. Busy around here, but I'll do my best...

Re: Merc 40HP ??

Thanks Garndawg, I'll keep checking back, much appreciated

Re: Merc 40HP ??

Garndawg
Just wondering if you had anytime yet or any luck with the link n' sink info?
Thanks!

Re: Merc 40HP ??

OK- Anyone?

Re: Merc 40HP ??

Update: Well, as I suspected, friends attempts to 'adjust' timing and linkages was a disaster. Took boat to river and made adjustments to spark advance went well. Carb low speed mixture was off a bunch too, fixed. Motor idles smoothly and now has full high end RPM's. He's a happy camper to say the least. I noticed a fuel leak at carb and installed a fresh carb rebuild kit after complete cleaning, all's well now.

One last concern tho...his choke solenoid has an open winding i.e. no electric choke. Friend claims there's no replacement available but I'll see what I can find.

Re: Merc 40HP *** Update

Re: Merc 40HP *** Update

Dupe post...

Re: Merc 40HP *** Update

Re: Merc 40HP *** Update

Glad to hear you got it running fine. Sorry, but been away from here for a while...

Can't help about the choke, as mine was closed-coil.