1980 Merc 40HP for the real Guru's

[James R]

I have been puzzling with this for a while. The timing is way out and the old trigger when rotated to the idle position would cut the sparks off. Thought it was the trigger but a new one does the same. Got to thinking. This motor has a bolt in flywheel center and it looks like the bolts have been removed and put back. I think the center, which carries the magnets for the trigger pulse, has been removed and replaced incorrectly. If you guys think the same what is a good procedure for getting it back in position.

 

[Faztbullet]

Re: 1980 Merc 40HP for the real Guru's

This motor has a bolt in flywheel center and it looks like the bolts have been removed and put back. I think the center, which carries the magnets for the trigger pulse, has been removed and replaced incorrectly.

The inner will only mount one way on crankshaft but the outer markings can be off. Get a dial indicator and check #1 TDC against marking on flywheel....

 

[James R]

Re: 1980 Merc 40HP for the real Guru's

Thanks Faztbullet, welcome aboard.
You were correct about the alignment. However, and there is usually one of these, I still loose the sparks as I approach the idle position with the trigger. Advance the trigger and the sparks come back good and strong. Any Idea what this might be. The switch box is a CDI and looks very new. The stator is a CDI and looks very new. I have isolated everything so that there is nothing outside of the trigger, switch box, stator and coils connected.

 

[Faztbullet]

Re: 1980 Merc 40HP for the real Guru's

I ran into a problem similar years ago as the hub magnet was not deep enough in the trigger. You could actually see under flywheel and about 1/4 of hub was above trigger. It ended up that someone replaced flywheel of incorrect year.

 

[James R]

Re: 1980 Merc 40HP for the real Guru's

Thanks Fazt. I noticed that there are two shim plates on this, one above and one below the fly wheel. I wonder if both should be below. I'll do some measuring and check it out.

 

[James R]

Re: 1980 Merc 40HP for the real Guru's

Nah, the shims will only raise or lower the flywheel relative to the hub magnet. The taper sets the hub height. Could be the wrong flywheel then. I will explore a little more.

 

[James R]

Re: 1980 Merc 40HP for the real Guru's

Pulled it apart again and the trigger magnet sits down nicely in the trigger. Can get it to just about run if I bring the trigger to partly advanced. Its not fuel as I have cleaned the carb, properly of course. No real reaction if I spray fuel in, bogs slightly. Very strange.
Could it be a failed Switch box?

 

[James R]

Re: 1980 Merc 40HP for the real Guru's

I may have it. Not being familiar with this motor and having a very poor manual, thats my excuse anyway, I think I was trying to operate with the ignition timing way out past the limit of the trigger. Having worked on it a little more I can see that I can keep sparks at least 2* ATDC and at least up to 20* BTDC. The original stops were way out. Now that I have figured that out what should the turning over timing sets be. Or what should the Idle and wot sets be in degrees. I have something about notches and windows in my manual. I know that is for a different model.

 

[James R]

Re: 1980 Merc 40HP for the real Guru's

No, still dont have it. My manual is not very good obviously. I expected the throttle butterfly to open at some point at the start of the movement of the trigger but it really doesn't move until the trigger is fully advanced to the stop. Yes there is a turnbuckle adjustment on the linkage but I have no idea what the position relationships of the throttle and the trigger should be. I cannot run the motor as outlined in the manual. I need a start point . The motor will chug at a point just off the idle stop but cuts out if I open up. Spraying fuel into the carb intake causes it to cut out. The plugs show fuel is going in ok.
Any help would be most appreciated.

 

[achris]

Re: 1980 Merc 40HP for the real Guru's

Idle set up process is to closed the throttle plate fully, then retard the timing until the desired idle speed is obtained. Remember that idle speed is set with the engine on the boat, in the water and in forward gear. You should also be adjusting the idle mixture at the same time. setting it to the best run, at the 'rich' end of that adjustment.

If the engine bogs when you open the throttle, set the idle mixture screw 1/4 turn richer and check again. You may need to advance the timing slightly to keep the idle speed within spec.

Chris.......

 

[James R]

Re: 1980 Merc 40HP for the real Guru's

Thanks for the response achris. This motor is in my shop and runs in a barrel outside. Have you any idea at what point in the trigger advance the throttle should be opening as the throttle barely opens when the trigger is full advance. If I set the trigger stop further out I loose sparks. Note it is a new trigger and has what appears to be new CDI switch box and stator.

 

[achris]

Re: 1980 Merc 40HP for the real Guru's

Thanks for the response achris. This motor is in my shop and runs in a barrel outside. Have you any idea at what point in the trigger advance the throttle should be opening as the throttle barely opens when the trigger is full advance. If I set the trigger stop further out I loose sparks. Note it is a new trigger and has what appears to be new CDI switch box and stator.

Currently in transit to home. I have the 40hp manual at home so will look it up and post the procedure for you when I get there (Wednesday morning).

Chris.......

In the meantime, I found an old Merc 'pocket guide' (as a PDF on my laptop) with the spec in it. I've extracted the 402 information and attached it for you. The pictures aren't up to much, but the text should point you in the right direction (till I get home).

View attachment 402 spec.pdf

 

[James R]

Re: 1980 Merc 40HP for the real Guru's

Thanks achris. Your info and my info keep reffering to dots and windows. I have the degree scale on the flywheel and the pointer so I have no idea what the timing should be at the set points.
Hope you have a safe trip home.
Ex pat POME.

 

[jslu]

Re: 1980 Merc 40HP for the real Guru's

]I have been puzzling with this for a while. The timing is way out and the old trigger when rotated to the idle position would cut the sparks off. Thought it was the trigger but a new one does the same. Got to thinking. This motor has a bolt in flywheel center and it looks like the bolts have been removed and put back. I think the center, which carries the magnets for the trigger pulse, has been removed and replaced incorrectly. If you guys think the same what is a good procedure for getting it back in position.[/

QUOTE]

James,

It really helps a whole lot if you have a mercury manual to better visualize the text. I have used this procedure many times over with great success.

John

 

[achris]

Re: 1980 Merc 40HP for the real Guru's

James, Just arrived home and I'll checking my manuals. I have the Merc genuine for 1979 to 1986, and it refers only to notches and windows, no degree scale. Can you give us your engine serial number. It may not be a 1980...

Chris.....

 

[James R]

Re: 1980 Merc 40HP for the real Guru's

You could be right Chris. 5751264.
Thanks.

 

[achris]

Re: 1980 Merc 40HP for the real Guru's

You could be right Chris. 5751264.
Thanks.

No, looks like you're right, 1980... Could you post photos of the power-head area?

 

[James R]

Re: 1980 Merc 40HP for the real Guru's

Thank for the response Chris. Give me a day or so. We have just received 8 inches of snow. Very unusual for the Charlotte area of North Carolina so everything is a mess. Will take pics and get back.

 

[James R]

Re: 1980 Merc 40HP for the real Guru's

Hi Chris. The snow is fast on the melt. Here are the pics you asked about and thanks for hanging in.

 

[achris]

Re: 1980 Merc 40HP for the real Guru's

I've had a look at your photos, thanks. All the parts look right, and are according to the parts catalog. You may want to put the starter housing back on, the notches referred to are on that. Can you find anything on that housing (when it's fitted) that resemble the instructions on 'link and synch'?

Chris.....