1978 Mercury stalling when put in gear great in neutral

[SSG Steelhead]

Greeting folks new to the forum and new again to boating. It has been 12 years since I last had a boat but the time has come again.

We got a 1978 Merc outboard that seems to start and run fine when not in gear. The second you put it in gear it stalls out. If you put the high idle on and "work it" in to gear it will run great until you drop the throttle down again.

It has been run this year a few times with no issue beyond that

I did put new gas/oil and additive in it

had the compression checked and it was "good" spark was present as well

Idle has been turned up with same issue happening, don't want to go too high as to cause issue with shifting and blowing the lower unit.

I have heard things from carb issues to electrical issues and everything in between

The thing looks clean and when I have seen it run it ran good. So where do I start and is it worth fixing and at what cost?

A million thanks in advance for your help here. I did some searching and have seen many things on this subject but not all the same end result.

Thanks again,

 

[MacDaddy21]

Re: 1978 Mercury stalling when put in gear great in neutral

What is the hp and serial number?

 

[ajgraz]

Re: 1978 Mercury stalling when put in gear great in neutral

^^^Agreed with that.

But first issue comes to mind for me is, maybe it needs a richer idle air/fuel setting. (i.e., turn the screws out more) When's the last time carbs were serviced?

Second issue that comes to mind, could you be over-propped?

 

[SSG Steelhead]

Re: 1978 Mercury stalling when put in gear great in neutral

It SN is 500**** not sure on the rest. Tells me it is a Merc M-800E (80 hp 4 cylinder)

Not sure the prop size or what it should be?

Not sure the carbs have been serviced in awhile.

Hope this helps narrow it down a bit. Thanks much!

 

[MacDaddy21]

Re: 1978 Mercury stalling when put in gear great in neutral

Before I say anything else, I just want to make sure you aren't running the motor in gear on the hose. You definitely dont want to get the RPMs up past idle speed. That can be bad on your motor.

Stalling out in gear or under load, is generally related to lack of fuel, which is carburetor/fuel pump trouble. If the carbs and fuel pump have not been cleaned and rebuilt in awhile, that is probably causing some trouble. Rebuild kits for those parts are readily available and cheap. If you do not have a manual for your motor, I suggest picking one up at your Merc dealer when you get your rebuild kits. Also, I would suggest getting a gallon of Chem-dip. Remove all the plastic parts on the carb, then completely disassemble both the carbs and the fuel pump. soak all the metal parts in the chem dip for a few hours, then rinse with water and allow to dry. The re-assemble using the new parts from the rebuild kits. If you know your way around carbs, its a simple job. A manual will help if you are rusty.

 

[SSG Steelhead]

Re: 1978 Mercury stalling when put in gear great in neutral

I have not run it in gear on the hose only in the lake.

Thanks for thehelp, I have never rebuilt a carb before but do have a manual not sure if this is something I can tackle myslef or not.

 

[MacDaddy21]

Re: 1978 Mercury stalling when put in gear great in neutral

Well, if you have any mechanical inclination at all, it should not be too difficult. It really is an easy job. To make it simple, just take pictures of each piece you take off, and where it came from. When I got my 1978 Merc 40, I had never taken a cowling off. I never bought a manual. For the carbs and fuel pump, you honestly just need to pay close attention to what you take off. And just do one carb at a time. The fuel pump is also very easy.

 

[MacDaddy21]

Re: 1978 Mercury stalling when put in gear great in neutral

Plus, most shops are going to want an arm and a leg to rebuild carbs and fuel pump, and they might have your motor for awhile.

 

[SSG Steelhead]

Re: 1978 Mercury stalling when put in gear great in neutral

Thanks, I will look into it but it is something I am willing to try for sure. THanks for the help.

 

[Mi duckdown]

Re: 1978 Mercury stalling when put in gear great in neutral

AND purchase an OEM Mercury manual. It will save lots of time on the computer.

 

[SSG Steelhead]

Re: 1978 Mercury stalling when put in gear great in neutral

Update.

Compression is between 131-136 psi

Not over propped

When it stalls it stalls like right now, not a dying out almost like you shut off the engine with the key. Control cable short??????

Carb mixture is +1 5/8 turns and carbs do not appear to dump much if at all.

Stator appears newer however trigger wires are not the greatest.

Thanks a ton guys!

 

[Maxz695]

Re: 1978 Mercury stalling when put in gear great in neutral

Thanks for the Comp reading that was gonna be my advise but Plugs will run up to a certain point and then fail to fire. MAKE SURE YOU HAVE GOOD PLUGS.I had this happen to me was running fine then all of a sudden I couldn,t get power over half throttle. I change the plugs with old ones I had and the sucker took of great again. Check for air leaks in fuel lines if your lines are old I suggest changing them Ethenol wears them down to a point where particles get into your carbs so much that inute particals mix with the gas making an engine smoke big white clouds of smoke. This will also affect the plugs

 

[SSG Steelhead]

Re: 1978 Mercury stalling when put in gear great in neutral

Update: pulled the control box (think you call it that) off and I did not see anything that stood out as a short. I do have to question the "switch" there that looks like it is depressed when the boat is put in gear and out when it is in neutral???

I did go to the outboard and followed the "trigger" wires (I think) down and one is only hanging on by a thread. I cut it off and will soldier a new wire on tomorrow and shrink tube it. Could that cause an issue with my problem? Or is it a work or not work issue with that. The wire comes from under the fly wheel on the backside to the electrical block on the starboard side a few terminals from the bottom.

I will figure this thing out and be pulling planner boards if it kills me!

Again when it dies it just "CUTS OUT" with no die back or choking out????

Thanks for the help.

 

[ajgraz]

Re: 1978 Mercury stalling when put in gear great in neutral

Bad trigger wire will (in effect) throw off spark timing wildly. Switchbox doesn't know when to fire. Fix that indeed. And check out all the other wiring under the cowl too, these old Mercs have really crappy wiring.

 

[SSG Steelhead]

UPDATE: 1978 Mercury stalling when put in gear great in neutral

UPDATE: 1978 Mercury stalling when put in gear great in neutral

I fixed the trigger wire.
I installed a tachometer so I could see where I was, I cleaned the carbs and rich'n up the carbs (1 5/8 is the factory setting, I am at a little over 2 now) and adjusted the idle stop. Lake tested it a few tims and she runs great. Bogs a little at approx 2200 rmp but good before and after that.

I swaped out the water pump to be safe and we are back on the water!

Thanks for all the ideas and help here! My wife was ready to set it on fire a few weeks back and now wants to go out every night!

Eric

 

[ajgraz]

Re: UPDATE: 1978 Mercury stalling when put in gear great in neutral

Re: UPDATE: 1978 Mercury stalling when put in gear great in neutral

Another 1/8 to 1/4 turn richer and I bet the 2200rpm mini-bog goes away.