GURUUUS: Jhnsn 50 hp boggin down

[ElRipper]

Ill try to post again. Gurus help me out ! 1986 Johnsonn 50 hp bogs down at higher rpm after running great for about 3 - 5 minutes. It starts right and purrs like a kitten, Responds well when throttled up. In the water it jumps out of the hole, planes up and scoots across the water like a champ. Then after 3 - 5 minutes it bopgs down like it runs out of gas. So i checked the throttle cable, ok, bulb hard and ok, air inlet to tank, ok, press on ball at end og line gas squirts out. So i put carbs kits in, no jets, super clean carbs, linkage operates great and together. Checked coil output, great, looked for points but has none, integrated, coils look new, no cracks in coating, all looks new under flywheel, does start up great and idles great, no misses, jumps or sputters, changed all line when i installed a new VRO ( $ 260), didnt help. Tried bypassing VRO, did mixture right, new plugs of course, pees good, changed impellor,thermostat, water and head gasket the year before. It srted acting this way before i did any of that work, has gotten persistant not to run after it runs great after 5 minutes. It will continue to run if I throttle way down at about 25 %,, moseys along, no missing or sputtering, throttle up it responds for about 1 to 2 seconds then down it goes. Cleaned tank, brass tube, air going intank, new gas lines, new bulb, coils good, throttle cable is not slipping, planes out good its not water lugging, thought it was electronic, but now back to sound like starving for gas. Next time maybe i will drain bowls to see if they are full or almost empty. I think i checked them once at the dock and they had gas. GUURRUUSS what is next ???? THANKSS
testoATcableoneDOT net

 

[ElRipper]

Re: GURUUUS: Jhnsn 50 hp boggin down

I also checked compression = @ 120 psi each, pees good, exhaust seems good, looked at carb throats while on muffs and gas is squirting in ..... Not sure what else to check..............thoughts ??????????

 

[Yamajoe]

Re: GURUUUS: Jhnsn 50 hp boggin down

Next time you take her out, at wot have someone squeeze the primer bulb when it bogs down, if your power returns the fuel pump should be serviced; remove the intake silencer assymbly have your mate look into the carbs when you are at wot, is there fuel spraying into each carb and do they look consistent? The carb which has low or no fuel spray is your culprit. If you regain power at wot by spraying premix fuel directly into the carbs, you have carb problems. Carbs need to be cleaned throughly. You should also vacuum test fuel system and insert a clear line into fuel line just before fuel pump to check for air bubbles, before you touch the pump.

 

[tashasdaddy]

Re: GURUUUS: Jhnsn 50 hp boggin down

i have and 87 50 i'm think carbs, one float needle sticking, not letting in enough gas to for wot supply. it's using the fuel in the bowl, then running low.

 

[ElRipper]

Re: GURUUUS: Jhnsn 50 hp boggin down

Thanks tashas pop and yama joe. The carbs dont have needles, and the fuel lines have been replaced. I cleaned the carbs like three times, they are whistling clean. Its gotta be a gas restriction. So I guess ill be crazy to crawl up there and look down the throats while hauling *** across the lake. Of course if its doing that my problem will be solved. Thanks dudes, I may put on a life jacket while pulling this stunt ???? he he he

 

[tashasdaddy]

Re: GURUUUS: Jhnsn 50 hp boggin down

your carb DOES have a float needle valve, it open and closes to allow new fuel into the carb. did you remove the low speed and high speed jets with the special tool? i have rebuilt those carbs many, many times.

 

[jay_merrill]

Re: GURUUUS: Jhnsn 50 hp boggin down

Good advice here and please bring someone with you when you check the carbs!

 

[ElRipper]

Re: GURUUUS: Jhnsn 50 hp boggin down

your carb DOES have a float needle valve, it open and closes to allow new fuel into the carb. did you remove the low speed and high speed jets with the special tool? i have rebuilt those carbs many, many times.

Yes sir, i understand the float needle valve. I dont find a mixture needle.
There is a pointed screw and the very bottom of the carb, i guess it may be called a needle. But if i understand it, this screw needs to be screwed in all the way. Now tell me if I am wrong, lets forget about the float needle for a minute....tell me about the brass screw below the bowl, behind the outer screw. This outer screw drains the bowl if loosened. Does this brass screw that resides behind this drain screw adjust mixture ?? It would be an internal adjustment if so, which i cannot find any information on, my books say this year carb doesnt have air/fuel mixture needles. Now I am wondering if this insert brass screw needs to be turned out some. It cant be done with the motor running because that outer screw has to be taken out first, drains the bowl. Hmmmm My manual doesnt address this brass insert........

 

[mstrud]

Re: GURUUUS: Jhnsn 50 hp boggin down

that brass peice is the high-speed oriface. It should be screwwed in securely, the little hole in it is what regulates fuel feed, hense its non-adjustable, just make sure its in and itll do its job. Now this issue you;re having sounds more like an ignition headache to me. I just had a simlar issue on my 93 50hp johnson. It ran great for 15 minutes then would bog down. turned out to be a bad power pack. take it out and run it till it bogs down, then pull each plug out 1 at a time and look for change, bring some thick rubber gloves. If you dont notice a change you've got no spark on that cyl.... ignition problems. Power packs are notorious for failing when they warm up.

 

[ElRipper]

Re: GURUUUS: Jhnsn 50 hp boggin down

Thanks mstrud, I will have to try that. When U say pull the plugs , I am assuming you mean pull the wire off, not take the plug out...... Good Idea.

When i took it in to a boat shop they said they checked the electrical while running it. I think they used a volt meter, or similar. They told me they saw no problems with the paks / coils or stator. The coils are sealed up good, no signs of wear or burns. I used to suspect the coils or power paks as heat and electricity will not work together, but after they told me that, I forgot about them as a culprit. I think it may be getting hot then the power paks could be failing. I will do the test you told me. Thanks !!!!!!!!