Idle issues 87 50hp

[philmay75]

Hi experts,

after two weeks on this I am finally asking for advice. First off, the motor is a 50hp Johnson 1987 Model J50LCUD and the current symptom is it wont stay idling. There is more detail below, but basically, on the muffs I can start it, it will run for about 60 seconds and if I dont intermittently press in the choke, it will die. I have disconnected the throttle cable until I get this idle issue fixed, but I really am at a loss. I've included a picture of the throttle linkage. Any input is much appreciated. My wife would really like me to get this boat out of her yard.



More Detail:
I'm working on this for my wife's friend who got taken for a ride by a mechanic. There are so many things I've had to walk thru that he messed up...but here is where I have done so far:

Compression Check: #1 = 89 / #2 = 82
Fuel Pump - VRO was toast, so I installed the OEM pump and took out the VRO. Changed out the fuel hoses while I was there.
Carbs - Carbs dont have adjustable jets, only fixed orifaces. Took the air silencer off, carbs off, (removed screw that was sitting on the intake reeds), rebuilt carbs, re-installed.

Put on an accessory tank with new gas just to rule that out. Seems like the only thing I haven't done is change out the plugs. :facepalm:

 

[bullcity101]

Re: Idle issues 87 50hp

I would check and see if the electric primer is working properly. In your picture it is the thing with the little red lever. The way the lever is now it is in automatic, meaning when you press the key in it squirts a little gas into the top end of the carb (idle circuit). If you turn the lever so it is perpendicular to the primer valve, counter clockwise, it goes into manual primer. That is when you squeeze the primer bulb it primes the top of the carb the same way it would if you press the key striaght in. I would try that to rule that out.

I didn't think this engine had a manual choke, I thought they switched to the electric primer so when you say you have to intermettently press in the choke, what do you mena?

 

[philmay75]

Re: Idle issues 87 50hp

Sorry, I am calling the electric primer "the choke." So yes, the only way it would stay running right now is if every 30 - 60 seconds I push in the primer button. And it seems to work because when it is about to die I can press the key in (prime it) and the motor will come back to life for another 30 seconds or so..

 

[mark1961]

Re: Idle issues 87 50hp

The compression numbers are low.....try a decarb and see if they come up some.....you really want to see numbers up around 100 or over.

You state the "VRO was toast".....would this mean it was run by the owner without oil?

 

[philmay75]

Re: Idle issues 87 50hp

You state the "VRO was toast".....would this mean it was run by the owner without oil?

Correct. Oil tank was empty, and the owner started pre-mixing her 50:1 and running it thru the fuel side of the VRO. I also stated it was toast because I filled up the float bowls, then attached the outlet hose to a bottle and the VRO wouldnt pump gas during cranking or running.

 

[mark1961]

Re: Idle issues 87 50hp

Correct. Oil tank was empty, and the owner started pre-mixing her 50:1 and running it thru the fuel side of the VRO. I also stated it was toast because I filled up the float bowls, then attached the outlet hose to a bottle and the VRO wouldnt pump gas during cranking or running.

So just to clarify, it has NOT been run without oil at any time that you are aware of?

 

[philmay75]

Re: Idle issues 87 50hp

I have no knowledge that it was run without oil. The story I got from her was that it started dying on her, she took it to a guy (who in her words turned out to be a meth head). He messed up the throttle and shift linkage from what I could tell. The VRO was as I described, there was an air silencer screw laying on the intake reeds for the top cylinder (reed looks ok and doesnt look damaged), there were only 2 screws left holding the air silencer to the carbs (instead of 6), the hose from crankcase to air silencer was disconnected, and there is probably more...but a lot of that is what I have been finding/fixing over the past two weeks.

He told her that her fuel tank had stuff in it so use an external tank...that's when the VRO stuff started...and when she got the boat back the idle was set at mid-WOT, wouldnt go into forward, etc. she called us when it failed on her at the lake and we went and hauled her in.

 

[mark1961]

Re: Idle issues 87 50hp

You have done the right thing and run compression check, the numbers you posted are low. For example, my twin cyl 60hp tests at 140. Ensure you have an accurate guage, maybe run another one the way it is for reference then go ahead and decarb, harder to do properly when it wont run for any length of time, will it keep running if you have the warmup lever raised? If you dont see any improvement in those numbers when you retest further investigation as to why is going to required.

http://forums.iboats.com/showthread.php?t=313963&highlight=compression

 

[philmay75]

Re: Idle issues 87 50hp

Compression on my ski boat with the same test kit is around 190 for all the cylinders, so I was the tester was ok, but that's a good point, I will go through it again. Also, I have some seafoam in the current tank for decarb purposes. Maybe I need to try and get it going enough to run the hoohah off of it on the lake...I also have an 89 johnson 25hp on my bass boat with similar compression (@90) that purrs like a kitten at idle.

As to the warmup lever. Let me ask a question...in theory, should the engine idle properly with the throttle cable disconnected (after its had a chance to warmup of course)? Ive never really had to do a link and sync on anything I've owned but found some decent instructions in my OEM manual. The throttle linkage between carbs seems right as I watch the blades. The throttle cam is on the timing marks for the follower, but I have no idea if our friend messed with the idle timing screw, or if that would even have any bearing on this issue.

and also...would this possibly be indicative of an air leak? I wonder just because priming it with the key pushed in keeps it running which means it appreciates having more fuel and is possibly running lean?

Very much appreciative for the input, BTW.

 

[philmay75]

Re: Idle issues 87 50hp

Ok, I did the propane trick and burst a little propane from my unlit torch to see which carb might be running a little lean. Bottom carb caused the RPMs to go up, so I took it apart again, and rebuilt it, again (including the core plugs again ). Put it back on and now it is idling, still rough, but it stays running.

But now the top carb is spitting little fuel droplets at me out the front. Does that possibly mean a reed issue? It seems now that it is running too rich because I can restrict the airflow to the carb slightly (placing hand in front of the throat with lightly spread fingers) and the RPM takes off.

Also, a question on the timing because the warm up lever is slow to respond. My flywheel has the following timing marks. They are 20/18 and 4/2 are painted. At idle on the muffs, the timing is between the 4 and 2 marks. Is that where it needs to be?

20 16 12 8 4 TDC
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[MACH1SCJ]

Re: Idle issues 87 50hp

What did you find out about the top carb spitting fuel droplets out?

 

[CharlieB]

Re: Idle issues 87 50hp

Some years came with lower compression.

Timing is critcal, follow the factory service manual to set WOT maximum timing, then check idle timing. Timing should advance slightly as the throttle takes up the slack between the cam and carb linkage roller. If the guy messed with all of these you will need to pay very close attention to the book to get it right.