'81 50hp stalling and rpm problem: Video included for you master mechanics :)

[Solomon Shaffer]

My '81 Mercury 50hp with some issues:


It stalls at low RPMS, is very hesitant to accelerate, and doesn't
run above aprox. 2500 RPMS under a load. Sometimes I have to
use starting fluid to get it started from cold...

I've replaced:
-Stator
-Fuel lines
-Sprayed Sea foam in carbs (Note on that: When I set it on a higher idle and sprayed the SF in the bottom carb, the motor sorta coughed & lugged under sightly (as I expected.) When I sprayed it in the top carb, the motor revved up pretty high. That probably means that the top carb is not getting [as much] fuel, correct?)

Previous owner rebuilt carbs in October.
Compression was good according to mechanic at
the Marina where the owner had it serviced.


Click here for video of problem (at idle)
(I do realize that by turning the gas thing that I'm turning, it's probably not advancing the spark...but it behaves this way if I'm up at the controls.)

 

[achris]

Re: '81 50hp stalling and rpm problem: Video included for you master mechanics

Do a cylinder drop test (pull the plug lead off each plug in turn and make sure each cylinder is contributing about the same to the running of the engine). If the engine increased revs when you sprayed SF in the top carb, it needs pulling off and cleaning... In future, don't use seaFoam, use Mercury Power Tune.... I haven't seen it but plenty of people on here report SeaFoam killing engines....

Chris.........

 

[Solomon Shaffer]

Re: '81 50hp stalling and rpm problem: Video included for you master mechanics

How hard is disassembling a carb on one of these?

Do I need to get new gaskets/fuel pump, etc or should I just clean it?

I'm thinking that I may just pull the carb off the motor and take it to my auto mechanic. He works on all kinds of stuff and he probably would actually get it back together! haha

 

[achris]

Re: '81 50hp stalling and rpm problem: Video included for you master mechanics

Do you have a service manual? If not, then get one. Even your auto mech will need it to set the carb up right.... (and do both at the same time. I would also service the fuel pump)...

Chris....

 

[Solomon Shaffer]

Re: '81 50hp stalling and rpm problem: Video included for you master mechanics

Yea I do have a manual. Part of me would really just like to take it to Merc dealer and get it fixed quickly...but I have no idea what that would cost! $80.00 an hour adds up pretty quick. (That's why I was going to to do it or have my mechanic do it...of course he doesn't have a test tank, etc, so it may end up being the same.)

 

[achris]

Re: '81 50hp stalling and rpm problem: Video included for you master mechanics

As long as you are reasonable with hand tools, and can follow the directions in the manual (a factory manual, not toilet paper. ie seloc/clymer) you shouldn't have any problems doing it yourself.

After you've taken the carbs off, strip them down, clean them and reassemble them one at a time. I would go through the synch adjustments after also.... Just to be sure the carbs are synched correctly.

Chris......

 

[chum1]

Re: '81 50hp stalling and rpm problem: Video included for you master mechanics

good vid., the trigger arm is usually moved to full deflection to the stop, then carbs kick in, don't know if that would help. you probably have two cyl's that arn't firing for whatever reason

 

[Solomon Shaffer]

Re: '81 50hp stalling and rpm problem: Video included for you master mechanics

Maybe my manuals are part of the problem...I have two that I've downloaded/purchased on CD from the internet.

For instance,as far as the fuel pump....where is it? I can't find my engine's setup in the manual. On my engine it looks like there is a pump for each carb. The lines come in from the quick-disconnect fitting, split at a T connection, and then go to the carbs. They hook to what looks like a diaphragm pump on each carb.

 

[achris]

Re: '81 50hp stalling and rpm problem: Video included for you master mechanics

Maybe my manuals are part of the problem...I have two that I've downloaded/purchased on CD from the internet.

That would make them seloc or clymer... Trash 'em....

Have a read of THIS thread on manuals...

For instance,as far as the fuel pump....where is it? I can't find my engine's setup in the manual. On my engine it looks like there is a pump for each carb. The lines come in from the quick-disconnect fitting, split at a T connection, and then go to the carbs. They hook to what looks like a diaphragm pump on each carb.

Get a factory manual and you'll have no problems.... Your engine does indeed have a fuel pump on each carb.... The factory manual will take you through all you need to know.... The manual you are looking for is 90-861355. Look on eBay or if you can afford, a Merc dealer ($81, but well spent)....

Chris........

 

[chum1]

Re: '81 50hp stalling and rpm problem: Video included for you master mechanics

here is a "free" service manual it covers these models:




go to this link, download and burn it to disk, then you can erase it off your hard drive and not bog down your memory or leave it on if you have a thousand jigawatts of mem. your choice.

http://www.myoutboardengine.com/file/

your carb i think is called a "b" carb and can be found on page 136

and there ya go

 

[chum1]

Re: '81 50hp stalling and rpm problem: Video included for you master mechanics

Oh sorry those bastages changed/removed the link, i will see if i can find another place to install it being that i have it on disk

 

[achris]

Re: '81 50hp stalling and rpm problem: Video included for you master mechanics

and that's a seloc or clymer, not a factory manual....

 

[Solomon Shaffer]

Re: '81 50hp stalling and rpm problem: Video included for you master mechanics

Thanks for the advice on manuals. I put in a request with some guy who sells factory manuals.

Turns out that my carb was in my cheap manuals (thanks chum ) I'm going to read over the rebuild process and see if I think it's clear enough for me to do them. I'm going to first pull the leads while its running to make sure that each cyl. is actually working properly.

 

[Solomon Shaffer]

Re: '81 50hp stalling and rpm problem: Video included for you master mechanics

OK, so I've been checking in my cheapo manual...and something is strange. The exploded view of the carb shows an "idle mixture screw" with procedures on how to adjust it once the carbs are rebuilt. I thought "Well, maybe it's out of adjustment and I could try that before I tear them down."

My carbs don't HAVE this screw. There's only one screw on that side of the carb and it's just a cap that covers the idle tube I believe. Where the idle mixture screw should be there is an indentation (like it was an option or something.) I take it there are NO adjustments on my carbs, then?

 

[achris]

Re: '81 50hp stalling and rpm problem: Video included for you master mechanics

It's #22 on this drawing...

 

[Solomon Shaffer]

Re: '81 50hp stalling and rpm problem: Video included for you master mechanics

Thanks, Chris! I'll check that out. That's very likely why I wasn't seeing it. I appreciate it!

I have an update:

I talked to my mechanic and he was telling me a few things to try and gave me some tips on the carbs. I went home and put a spark tester on all the cylinders. All are firing.

Then I did something that I'm not sure I was supposed to do: I noticed that there was a good bit of travel on the throttle/shifter control. Meaning that I have to move it several inches before it would move anything back at the engine (except for the Fwrd/Rvrs).

So I disconnected that cable at the engine, put that arm (don't know what it is called - it goes to the trigger, etc) in a spot where the engine idled nicely, then I adjusted the cable accordingly and reconnected it. It accelerated fine in the tank so I decided to run to the lake.

It needed starting fluid to get it going, but it idled great out through the inlet, and then I slowly gave it gas and it went to WOT! Yeah ! It was great!

But after about 5 minutes of WOT it suddenly cut the RPMS, returned to idle, and that's all it would do. Return to dock.

So now I'm REALLY not sure what to do.

Am I correct in saying that it's probably not a carb/fuel pump problem? A fuel problem wouldn't be intermittent, would it? Not sure
(I did notice that the fuel filter does not always stay full. It sometimes looks like there's hardly any in it so I'll pump it up.)

I'm encouraged because it did open up, but I sure am confused as to what to do next! (besides, now I REALLY want to be out on the lake )

 

[achris]

Re: '81 50hp stalling and rpm problem: Video included for you master mechanics

So I disconnected that cable at the engine, put that arm (don't know what it is called - it goes to the trigger, etc) in a spot where the engine idled nicely, then I adjusted the cable accordingly and reconnected it.

Not really the right way to adjust the idle speed... Look in your manual.

It accelerated fine in the tank so I decided to run to the lake.

It needed starting fluid to get it going

That's a bad sign.... You need to get those carbs off and clean them out. You should NEVER use starting fluid in an outboard, unless you want to go shopping for a new one some time soon.

, but it idled great out through the inlet, and then I slowly gave it gas and it went to WOT! Yeah ! It was great!

But after about 5 minutes of WOT it suddenly cut the RPMS, returned to idle, and that's all it would do. Return to dock.

So now I'm REALLY not sure what to do.

Am I correct in saying that it's probably not a carb/fuel pump problem? A fuel problem wouldn't be intermittent, would it? Not sure
(I did notice that the fuel filter does not always stay full. It sometimes looks like there's hardly any in it so I'll pump it up.)

I'm encouraged because it did open up, but I sure am confused as to what to do next! (besides, now I REALLY want to be out on the lake )

Fuel problems can be intermittent... If the filter is filling with air... You may have an air leak in the lines somewhere..

Chris.......

 

[Solomon Shaffer]

Re: '81 50hp stalling and rpm problem: Video included for you master mechanics

I'm thinking that I should check out the fuel line 1st, right? (I have checked all the hose clamps and made sure they were tight. I might get a new bulb, filter and fuel line just to be safe.) I'm really hating to pull the carbs if it's something simple. I want to rule all of that out first....

 

[Solomon Shaffer]

Re: '81 50hp stalling and rpm problem: Video included for you master mechanics

Very interesting.....I was reading on another thread about a fault primer bulb. I emptied mine of fuel and shook it, it rattled. So I cut it open and sure enough, one of the little valve thingys had popped out.

I also found the idle mixture screws so I'll be checking on them after the new bulb is installed. This could be easy...... (Probably not.........!)

 

[Solomon Shaffer]

Re: '81 50hp stalling and rpm problem....now what!? (updated)

Re: '81 50hp stalling and rpm problem....now what!? (updated)

Thanks to the new primer bulb and fuel line, it starts without starting fluid.

But the stalling problem still exists. I started fine, ran at a nice, slow speed through the inlet, but when I tried to accelerate on the main lake, it started dogging down and then it would stall.

I came home and took the top carb apart. Aside from a little bit of junk in the float bowl, everything looks great. It's obvious that the carbs HAVE been rebuilt recently. All gaskets, the fuel pump diaphragm, etc are in great, new looking condition.

The only other thing was on the idle mixture needle, there was a hairline scratch around it. Would that be enough to do this? Everything else looks fine.

Now I've got to try to put this carb back together. Any ideas as to what I should clean the clean parts in??