Stuck at MAX revs 2000 50HP Johnson

[racerone]

I believe there is an issue with the throttle plates stuck OPEN.

 

[lindy46]

In your pic the carb roller is not even close to touching the cam. Something isn't right. Looks like the carb butterfly isn't anywhere near closed. Also, looks like the clear plastic coating on both rollers is missing. You need to go through the proper synchronization procedure step by step.

 

[RBoyd1971]

Yea, that is an obvious one there! Geeze! Surprised is didn't blow a rod.

 

[Jonny1/2Cab]

And the winners are ................... Racerone and tblshur, Trottle stuck open, causing butterfly valves in carbs was the problem. The offender was a loose bolt. C!@NT of a thing jammed the bottom carb open causing the over-revving. I reassembled the unit and it ran rough for a bit and then stopped - Thinking it was I'd forgotten to reconnect the fuel was not it. The problem is it does not run anymore. I took it to a mechanic who confirmed I am not mad and that there is something else now wrong with it now. All reassembled linkages are as they should be. Compression = 140 both cylinders, Spark is very strong, Timing is as it should be. Fuel is being delivered to carbys. It after fires (ignites in the exhaust -as opposed to backfire that comes through the carbys if anyone didn't know, I didn't - this mechanic was very particular with explaining the difference) but does not run . We even entertained I had mixed the ignition leads-wrong. Carbys coming off tomorrow for a cleanout and test, IF that's a fail, the next step is to remove the next engine plate to inspect the Reeds. Worst case scenario is a second bolt has made its way internally and has damaged the reed valves. Wish me luck. 2020 can go and get F!@##$

 

[racerone]

Did you torque the flywheel nut to 102.5 FT-LBS after inspecting the key ?

 

[lindy46]

Here's a pic of mine properly set up at idle. Note: on 50hp model, the roller does not align with the two arrows on the throttle cam. There should be about 1/2 inch clearance between the head of the idle adjustment screw and the spark lever assembly. Yours is backed out way too far.

 

[RBoyd1971]

So I'll ask the obvious, where did the loose bolts come from?

 

[ct1762@gmail.com]

seeing the pic, i thought you had backed the cam roller away from the throttle cam! wow. but did you follow the factory synch n link to a T? these are very sensitive to synchronization. all linkages have to be the exact length of what they say in the manual. i can tell you by the pic that the linkage just under the flywheel is way off. believe it needs to be 5.3cm . hoping it didn't ingest one of those air silencer plate 5/16'' screws. are they all in place? they need 30 n/lbs and some blue threadlocker.

 

[Jonny1/2Cab]

Did you torque the flywheel nut to 102.5 FT-LBS after inspecting the key ?

Sure Did

 

[Jonny1/2Cab]

So I'll ask the obvious, where did the loose bolts come from?

Air box mounting bolt - no thread locker. One is missing

 

[Jonny1/2Cab]

UPDATE -
But first for or those that didn't read this part
"I took it to a mechanic who confirmed I am not mad and that there is something else now wrong with it now. All reassembled linkages are as they should be. Compression = 140 both cylinders, Spark is very strong, Timing is as it should be. Fuel is being delivered to carbys. It after fires (ignites in the exhaust -as opposed to backfire that comes through the carbys if anyone didn't know, I didn't - this mechanic was very particular with explaining the difference) but does not run . We even entertained I had mixed the ignition leads-wrong. Carbys coming off tomorrow for a cleanout and test, IF that's a fail, the next step is to remove the next engine plate to inspect the Reeds. Worst case scenario is a second bolt has made its way internally and has damaged the reed valves. Wish me luck. 2020 can go and get F!@##$"

Carbys have come off and been thoroughly cleaned and in the process, I found another offending object. This time it was further in, stuck in one of the leaf valves. (Pic attached) -a wiring connector.????

Another Mystery to me are the carbys themselves- they look identical, but have different throat diameters. THIS CAN'T BE CORRECT -Right? - 3rd Pic .

Clearly, there are a few things to address by my regular mechanic who put this one on the boat when he comes back from Chrissy break. To his credit, he'll fix it without question for free, Just a bit frustrating waiting. AND, the engine was running perfectly until the bolt issue that caused the rev problem.

Anyhoo - Thanks to all for the help and advice. I'm back at work now so won't be tinkering anymore until Fred gets a look at the damage. I will keep you all updated with the result.

Thanks again and I hope 2021 is better for all.

Cheers Jon

 

[lindy46]

Both carbs should be the same.

 

[juno pierrat]

looking at parts diagram, leads me to believe that both carbs are wrong, 2000 50 hp carbs don't have the idle orifice at the top of the carbs like the ones in the picture!

 

[webbd]

UPDATE -
But first for or those that didn't read this part
"I took it to a mechanic who confirmed I am not mad and that there is something else now wrong with it now. All reassembled linkages are as they should be. Compression = 140 both cylinders, Spark is very strong, Timing is as it should be.

Hi Jon,

When I looked at the first pic you sent of your engine, I could see that the throttle cam roller was stuck and not following the cam. Throttle plates were locked open.

After-firing: After you removed the flywheel, did everything go back together correctly? If the flywheel didn't seat properly on the key, it would look like timing is correct, because a timing light would read off the flywheel, but it wouldn't be correct because the flywheel isn't synched with the crankshaft. I'm wondering if the key fell out when you put the flywheel back on.

- DW

 

[lindy46]

looking at parts diagram, leads me to believe that both carbs are wrong, 2000 50 hp carbs don't have the idle orifice at the top of the carbs like the ones in the picture!

Yeah those are not the original carbs for a 2000 Johnson 50hp 2 stroke. See the pic I posted of my motor and compare to your motor.

 

[juno pierrat]

sorry about all the bad news on the carbs, Any updates on the motor?

 

[ct1762@gmail.com]

the one on the right could very well be from an early 56ci 70hp! i'd be very interested to know what jets were in them, especially the high speeds! im sure i have a set. been going through some parts for a 2001 135hp upcoming rebuild project and came across a whole bin of them i had collected and forgot about. know how hard it is to get parts for these in Australia (assume that's were you are sorry if it's New Zealand or something)