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1986 Johnson 90 VRO - Bogging/Stuttering

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QTwo

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Having some perplexing issues with an 19865 or 86 Johnson 90 HP VRO (see thread in in what year forum) that I am trying to narrow down. The issue centers on a bogging and shuddering/stuttering under acceleration that I am having a h&!! of a time figuring out. I am not trying to write a book here, but probably best to show what I have done to give a better overall picture.

When I first put the boat in the water for the initial shakedown test, started out fine for about the first 5 minutes. Wasn’t coming up to full speed and certainly not singing like usual. The revs were only about 4500 (motor shows as 5500 redline), but then it just started bogging down and dying under power. Still ran in idle but would not accelerate when in gear. Tried to pump the ball but wouldn't stay firm.

Dragged it out and went about checking the usual culprits. Fuel filter was clean, but bought a new one. Took off the carbs, cleaned them up, blew out all parts and rebuilt as it had been a few years. Noticed that the primer solenoid had a small gas leak so I bought a repair kit that included gaskets, valve, o-rings, etc. I also replaced some of the internal fuel lines and vacuum hoses. I did NOT replace any of the fuel line from the portable tank to the engine as this was done 2 years ago. Took for another test cruise and was even worse than before. Pumping the fuel bulb didn’t help at all, and neither did pushing the primer.

Dragged it back, again, to start the next round of diagnosis. Because it was bogging and seemed fuel starved, I was sure it was a fuel issue. Had no way to check if the tank vent cap might be clogged up (10+ years old), so I bought a new gas tank. Checked the fuel line hose and discovered that ethanol had done its nasty job. The inner lining (sierra assembly) had pulled away and collapsed, so this was replaced. Also pulled the carbs again as saw a small fuel leak. Opened them up and found 1 of the frost caps had come loose, and two of the vacuum lines between the upper and lower carb had torn at the nipple - fixed. The fuel line pumped up hard, the clear filter filled and held gas, engine started right up. The idle was still a bit rough at times and sputtered every little bit, but not entirely out of normal.

Took it out for another shakedown cruise. Started up fine, would get underway but as soon as I went to about 2,000 rpm's the bogging came back as did the shuddering. Would eventually get up to about 3500 at full throttle but felt terrible like it has emphezema. The idle was back to rough, acceleration thereafter was tepid and the strange part was it came and went, not consistent. Pumping the bulb or primer did nothing at all. I have exhausted all of my fuel related diagnosis.

Now I am at:
- Power Pack? One of them was previously replaced, different colors - one blue, one black. A ground on the black was showing some corrosion and only hanging by 1 or 2 strands. I replaced with a new connector and took out again, a little better, but not much. Also strange that now the tach was not working so couldn't tell the rpm's. Would the power pack cause an intermittent issue, drop out at higher rpm? Or just not run at all?

- Plug wires? Not sure last time replaced, easy enough to order

- Coils? Didn’t have a multi meter handy and in middle of day, so couldnt see if a spark. Would these cause an intermittent problem, be weak or just not work, so running on 3 cylinders vs 4?

Any ideas to help diagnose? I took a video of the boat accelerating but have to find a way to upload.

Thank you
 
As Racer said, check your spark. Here is a really easy tool I built for testing. Racer did it even easier, he just glued wires to a piece of cardboard.
 

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Thank you for the replys. The compression range is from 115 to 120.

Edchris, not sure what I am looking at for your spark tester or how to use. Someplace I can go to see how it works?
 
Remove all spark plugs,
Screw the small bolt into the plug boot of the cylinder you are testing. The 1/4” bolt just ensures a good connection.
Place the other bare end in the spark plug hole, the weight of the tool will keep the wire on an angle, held against the sides of the plug hole- this provides a good ground.
Bend the two short bare wires to about 7/16” gap.
Now crank, or pull as if trying to start the motor- you should easily see a bright blue spark jumping the gap. If it doesn’t, investigate ignition problems.
If you get no spark at all, 1st make sure your ground wire is making good contact.
 
A quick update on the problem and solution. I purchased new plug wires and swapped out, this solved the issue. One of the plug wire coverings had been damaged exposing the wire. This in turn was "bouncing" around and would cut out that cylinder but not in a detectable pattern.

The original problem was with the fuel lines from the tank, damn ethanol. Replacing those, many internal lines, rebuilding the carbs and other minor things were certainly very frustrating, and spendy, but hoping all is good for a couple years to come. To guard against the ethanol issue, I am searching for No ethanol gas stations to use moving forward. I will also be doing the Sea-Foam'ing this weekend to clean out any residual inside the engine.

Thank you all for your feedback to help me solve the problem.

Happy Boating!
 
QTwo said:
To guard against the ethanol issue, I am searching for No ethanol gas stations to use moving forward. I will also be doing the Sea-Foam'ing this weekend to clean out any residual inside the engine.!
Click to expand...
Good you got it sorted out.
However, your final efforts are somewhat misguided. As you discovered, ethanol is destructive to older fuel lines. If you replaced these, (completely, from tank to pump to motor), with new, quality lines, they will not be affected by ethanol.
Ethanol is an alcohol, & all alcohols are good solvents, that is why cars today, 20 years old, with 300K on the odometer have never had problems with those tiny passages in fuel injectors, ethanol keeps things clean.
What clogged your fuel system was not ethanol,(an alcohol), but pieces of degraded fuel lines...buckets of Seafoam will not clean or remove that debris. From the MDS sheet, Seafoam is 95% isopropanol, an alcohol. It’s a very expensive way to put alcohol into your fuel. Scroll down to Section 3
Interestingly, a few of their “different products”, have the same composition. Deep Creep, & Seafoam Spray show the same composition. The same product sheets show slightly different in Canada than the USA.
You may have read internet articles about Seafoaming engines, with the author stating, look at all that smoke...the carbon being burned out of the engine.
That is factually wrong. Seafoam states it is safe for all 2 & 4 stroke engines. How can alcohol be sprayed into a 2 stroke kicker, without it seizing up?
Seafoam Spray contains mostly “hydrocarbon blends, or petroleum distillates”, to lubricate the engine. Dump some extra oil into any engine, let it sit then fire up & you are going to see smoke- burning that oil causes smoke. No different than starting your lawn tractor after spraying fogging oil into the intake.
Good practices, keeping dirt & rain out of your system goes a long way to keeping engines running well. A can of Miracle Shyte in your tanks is mostly money out of your wallet.
https://seafoamworks.com/uploads/2021/05/1420-SS-4001CA-SS-SDS-CA-ENG-v20210526-sfi.pdf
https://seafoamworks.com/uploads/2019/09/SDS-SFMT-US-ENG-v20190905-1.pdf
Ethanol gets a bad rap, deserved, in older fuel lines/systems that were not compatible. The other issue is phases separation, which occurs because all alcohols are very good at absorbing, or mixing with water. Once it absorbs a certain amount, it separates, making the entire fuel load useless. If you don’t leave your fuel system open to rain etc, & you use the fuel in a relatively short time, there is nothing wrong with fuels containing up to 10% ethanol, & the ethanol will keep things clean.
“Regular” gas has a shorter shelf life, if your boat sits for extended periods I would use non ethanol.
Most “Premium” grades are zero, or very low ethanol content. Shell V-Power claims zero ethanol.
Lastly, it took 30 some years for ethanol to degrade your old system, it will take more than that to degrade your new lines...will that engine die from other issues before 2051?
 
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Good info on the ethanol. I updated the fuel lines to what I believe are high quality lines, but that is what I thought 2 years ago when I bought the new line from the console to the engine. Time will tell.

Now I am trying to figure out another, more expensive issue that just happened. This years boating story started with me trying to raise the motor on my old Boston Whaler. This is probably a new thread, but not sure where this would go.

My plan was to move up the motor a few holes and get a new stainless steel prop to give a better hole shot and higher top end. I also installed a tach and downloaded a speedo app to see the results. I purchased an OMC SST stainless prop off EBay that was listed as new. Appeared to be in great shape in the pictures and looked great when I received. Fast forward - Left the current prop on while I was trying to figure out the fueling issue that turned into the spark wire issue. Finally got the parts and problem figured out last week. Took the boat out for some testing runs with the current prop this past Saturday morning. Changed up to the new prop and went out for a warm up run to make sure all was well with the new prop. Smooth operation, no issues and went back in. The expensive problem occurred when I went back out later to do some testing. Just as I was coming up to mid-range speed, the boat lost all thrust slamming me forward, the engine raced to a high rev and I yanked back the throttle. Raised the motor up and all I saw was a rubber hub, castle nut and cotter pin, intact - WTF! The propeller had spun off and was now swimming with the fishes 50 feet down. No slipping, no tell tales, just gone.

Anyone ever heard of this? I have found info on spun hubs, but that is the splines breaking loose and the prop just spinning on the shaft, not being lost for good. Any ideas? Move this to a separate thread?
 
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