Final Straw.

[JustWarminUp]

Hello, I am looking into an issue that I have chased with both time and money for a year now to no avail.

When I go to take off, i have up to half throttle any further and it dies almost Immediately, I can SLOWLY coax is to full throttle or if I Pop the throttle Little to Full again and again really fast about 3times I can sometimes leave it at full throttle and it will run, when finally get it to go full throttle it will keep going till I let off, if i put it down quick then try to go back to full it will die.

It's a 1983 Johnson 50hp.
New
Coils, power pack, Spark Plugs, plug wires, fuel pump, fuel lines (From pump to carbs) and (From connector on motor to pump) , fuel primer ball, and fuel lines with connections to motor and tank, gas tank, rectifier, both carbs professionally rebuild with full kit.

Synchronized the Timing using John Reeves method.
New fuel, correct oil mixture, with and without cap on gas tank.

Compression is 140 both cylinder.

I have pulled both reeds and head, replaced both gaskets, no previous leaks either. Doesnt run HOT either, while running i can lay my hand ontop of the head.

 

[oldboat1]

Is the throttle cable slipping (remote cable)? Don't mean to be insulting, but often an overlooked simple issue. Is spark strong and consistent? You can check for dropped spark (i.e., dropped cylinder) using a timing light -- no flash, no spark. Use an open air adjustable tester and measure spark when at the dock or in the driveway.

 

[JustWarminUp]

When using timing light, it was strong and consistent.

Cables are also new as well as controller (2020 omc model

I am going out again tomorrow, I'm going to try adjusting the timing 1-2 degrees in either direction with the light and see what happens. I do not have an open air tester, I just tied a wire to the block and wrap a 1-2" amount of wires tightly around the threads of the plug.

If I means anything the zap I caught hurt like a mother and was like catching a quick little one from a 120v outlet like when plugging in crappy Christmas lights with your hand on a bad bulb.

 

[F_R]

Sounds like a classic case of carburetors opening before full timing advance. When that happens it will surely stumble and often conk out.

Watch the carb throttles as you advance the throttle (motor not running is ok for this check). The carbs should open just a little bit before the timing goes to full advance. THEN they should open fully with further throttle lever movement. Usual cause is a sticky timer base.

 

[JustWarminUp]

I'm definitely going to check that tomorrow!
So as the timing base moves, the throttle plates should hardly open, once advancement has taken place the throttle plates should then go up the steep increase, on the roller assembly?

 

[F_R]

I'm definitely going to check that tomorrow!
So as the timing base moves, the throttle plates should hardly open, once advancement has taken place the throttle plates should then go up the steep increase, on the roller assembly?

That's the general idea. Of course there is a little bit more to it than that. The timing and carbs have to be finely synchronized----what we call "Link & Sync" But that doesn't change unless somebody has messed with it.

Sticky timer bases are somewhat common and often overlooked.

 

[JustWarminUp]

Is there a procedure I can look up for mine? Or just a general basic?

 

[F_R]

You need the model-specific service manual to do that. But for now, don't get all hung up on that because unless it is really screwed up badly, that is not the problem.

 

[racerone]

And pumping the throttle handles means little as there are no accelerator pumps in carburetors.----You have verified that flywheel key is not sheared ?------Water pump impeller replaced ?-----The cylinder head was warped , so did you resurface / flatten it before installing with new gasket ?

 

[F_R]

I theorize that by pumping the throttle you are applying back-and-forth pressure on the timer base, hoping to unstick it to go to full advance.

 

[James R]

Sounds like fuel starvation.
Try this, Remove the front cover of the air box. Fill a spray bottle with fuel mix. Take the thing to the pond and get it going. When the motor starts to falter spray fuel mix into the carb intakes. If the motor picks up you have found that it is a fuel problem. Now we can sort it out. I hope I am right but the test costs nothing. Oh by the way please don't fall off the boat if the motor picks up. Also, If the carb floats are incorrectly set that can cause a similar issue.

 

[JustWarminUp]

So i got back out today, I bought the specific manual last night and looked into the link & Sync proceedure. So I adjusted some of the linkages to better fit the idea of "Little to no Carb plate movements, until the spark advanced had taken place" (not touching the timing advancement stop screw, I had already set that previous) it seemed to make the smallest difference but still has the same issues and resolved nothing. I'm going to attempt a full Timing proceedure at 100% throttle while still on the trailer this weekend by backing it into the lake enough to submerge the motor. Maybe during the adjustments It messed with the timing again?

Today I was wondering if it was a starving fuel issue so I tried pumping the ball and it was stiff with little to no play, pushed and jiggled the tank connections at that same time as well, nothing changed.

yes I have taken the flywheel off before to check the stater at one point, found some wire shielding that was becoming worn, I used shrink sleeves along from the the part where the wires come out to within a 1/2" of the end connection and replaced the connectors, made sure to put the stater back in the EXACT spot I removed it from. key is intact with 0 signs of wear or tear. surfaces for the head were flat and unwarped and mounting surface. telltale spits water a mile and after running for a very long time at any throttle I can get it to I can lay my hand on the head/block above the spark plugs with no problem.

As for when pumping it, It seems that's the only way I can fight the stumble at mid throttle that usually ends up killing the motor, which then gives me a full throttle till I go back down past half.

The timing base seems to move with the throttle linkages fairly easy, and returns easily as well.

I might be taking the carbs off again and looking through every part of them again, just to double check, but the fact I can get full throttle by pumping tells me it's not that..

 

[JustWarminUp]

So after reading a huge piece of the manual and studying pictures, I think my Linkages are all messed up, i dont think my max advance is correct or the timing or the Throttle cam and cam follower.

 

[racerone]

The factory went to great effort to set all the linkages.------These things generally do not go out of adjustment.----Yet many folks use the ---" I will try to move this and see if it runs better " ---approach .-----Instead of some real trouble shooting.----Sorry, just my opinion.

 

[JustWarminUp]

Well I'm going to have to give it everything I can to try and set them.

So should i just start from the first adjustment in the manual and work my way through them all by going down the list, or is there an order to the madness?


How I got the nightmare motor...
when i got the motor it was on a boat, it had the original controller but the older gentleman nearing his 80s that owned it had screwed wooden blocks around the controller to ever prevent it from going too far in any direction and he said he never drove it fast and only ever putz around the lake with him and his wife. I haven't never gotten it to run right.
But i put it on mine (my old one had given up) and installed the new controller, I always had low speed, but with a chugging or stalling. Just this year the father in law was who figured out we could get full throttle by pumping it.

After replacing almost everything. I did find some bad ones, power pack, rectifier, 1 coil, plugs, and 1 carb was not tuned, plus a HUGE amount of crap fuel lines ect. All these kept telling me it was more so a thing then anything else since I was finding problems as I went. So now I'm excited, hopefully I can get those Linkages lined up and be on the way.

All that's left after this is the Stator, and I need to do a test, it ohms out nice, but i have a DVA that I will use to check if its 100% good.

 

[oldboat1]

Spark testers can be had cheaply at an auto parts store (adjustable, open air type, rather than the inline style). If the spark measures 1/2 inch and is sharp, the ignition is doing its job (stator and coils OK). For stator/rectifier function, you would also look for proper battery charging.

I would try spraying WD-40 under the flywheel and rocking it manually (engine off). See if you can cut through the grease build-up that is probably causing problems.

I always work in carb cleaning with my motors -- full dismantle, soak and poke, carb spray in every orifice.

 

[JustWarminUp]

So ill shoot some WD up under to cut the grease, I'm going to work that throttle cam for the timing like the manual states, and then adjust the max advance.

See what happens. I'm going to buy an air gap tester tomorrow.

 

[oldboat1]

sounds like a plan.

 

[JustWarminUp]

I will keep everyone posted, if any know does know of the process at which linkages to do first I would definitely take an order at which to do them in, otherwise I'll work from the first page linkages appear in the manual and work my way farther through the book.

 

[oldboat1]

Chance you are carrying a large load of water under the floor -- weight shifts fore and aft?