1973 Johnson 65 HP, "Bogs" on accel

[The Mechanic]

Hi All,

This is my first post. Let me just say that you guy/gals are great. From the knowledge I have gained from reading your posts, I have been able to work through most of my problems, however, I now have a problem that I need to tap the experts on.

I have a 1973 Johnson 65 HP, Model: 65ESL-73R.

SYMPTOM: No acceleration after being off for approximately 30 minutes.

DETAILS: After idling about 5 minutes through a no wake zone, then running at WOT for 10 minutes to my fishing hole, the motor is shut off while I drift and fish. After about 30 minutes, the motor starts right up but "bogs" when I try to accelerate and subsequently dies. If I walk to the back of the boat and push the primer bulb a couple of times (although, the bulb is still relatively hard), the motor starts right up and then idles and accelerates normally. Also, after the 30 minute drift, I have tried pushing the primer bulb (which is still relatively hard), before cranking the motor, with the same result - "bog" on acceleration then dies. If I crank it first, let it idle, try to accelerate until it dies, pump the bulb, then restart the motor, all is normal. Furthermore, when I do get it to perform normally, I can run it for 3 to 4 minutes (to the next fishing hole), shut it off and end up with the same symptoms.

TESTING AND ADJUSTMENTS: Compression on #1,2 and 3 are 120, 115 and 110 respectively. New spark plugs. New primer bulb. Performed "link and sync" per OEM manual. Checked and adjusted timing advance. Disassembled and cleaned carburetors. Disassembled and cleaned fuel pump. Checked fuel hoses and fittings for defects and serviced as necessary. Secured all fuel hose to fittings with OMC nylon ties. New water pump. Drained fuel bowls, after an overnight sit, to confirm the presence of fuel in the bowls.

Am I missing something?

I'm sorry for the long post. I just want to try and paint the compete picture for you.

Thanks for any input or ideas you may have.

 

[tashasdaddy]

Re: 1973 Johnson 65 HP, "Bogs" on accel

ethanol poisioning. http://forums.iboats.com/showthread.php?t=299680

 

[The Mechanic]

Re: 1973 Johnson 65 HP, "Bogs" on accel

Thanks for the reply Tashasdaddy, I guess I should have mentioned that the fuel hoses and pump were replaced, approximately 2 years ago with alcohol resistant components. I had the carbs apart the other day and they were clean as a whistle.

Thanks for the link, lots of good information there!

 

[Ironguts]

Re: 1973 Johnson 65 HP, "Bogs" on accel

Sounds like a fuel delivery or contamination problem. Did you use a rebuild kit for the carb and fuel pump? You might want replace all fuel lines even if they look ok. I'd completely drain and clean the fuel tank. You never know what's lurking at the bottom of the tank unless you drain it completely. The fuel will begin to separate from contaminants when it's sitting for just a short while. When you press the bulb, some back pressure will go into the pick-up and may be enough to swish the fuel and mix it up bit. That, or the moment of you going to the back of the boat might be enough to mix it a bit. The pick-up is at the bottom of the tank, right where the contaminants lurk. Just a thought, but it seems like a logical explanation for your symptoms. If not, then using the rebuild kits and replacing all the lines should take care of the problem.

 

[Rick Thomas]

Re: 1973 Johnson 65 HP, "Bogs" on accel

Hey Bud,
I'm having a similar problem with mine, except mine doesnt die. I have the exact same Motor as you, save for the '75 Gearcase (forward & reverse are backwards). I Run the boat for a while hit my sink hole, fish for flathead for a couple hours fire it back up and its a dog the rest of the day. (max 2500ish RPM) My Fuel bulb is hard as a rock, it starts, restarts, and idles just fine., I have fresh gas and a clean mix yet still can't get any power after a couple hours of running her at 4K'ish RPM. Tomorrow I am going to haul it back out to the river and start pulling plug wires see if I can get her to "not" bog on a cylinder.

The local mech at the boat shop mentioned the Powerpack going bad on these motors relatively often. It's a $100 fix and might be worth checking into. Has the motor been stored for any length of time? Before I bought mine it was stored for 12years. Hence the '75 Gearcase the lower unit on the '73 froze and blew out the sides.

From my experience working on cars. Drivability = Spark, Fuel, Compression. Same for outboard boat motors. Except on yours you have 3 cylinders, 3 coils, and 3 carburetors. Ever Try tuning an Older 440 6pack. Its a pain in the proverbial "Arse"!

 

[The Mechanic]

Re: 1973 Johnson 65 HP, "Bogs" on accel

As an update:

I emptied, flushed and refilled the tank. I then flushed the primer bulb and fuel lines. I then pulled the drains on the carbs and flushed the needles/seats and bowls. I did take a fuel sample after flushing the primer bulb and fuel lines, looks good - no debris/water.

I ran it, same problem.

Further Observations:

If I raise the RPM's, while in neutral, it seems to "clear its throat" then all is normal (BTW, I was able to increase the neutral RPM by backing off the adjustment stop screw for the warm up lever). Now the warm up lever is set to a RPM quite a bit higher than spec.

Should I leave well enough alone and just use the "clear its throat" procedure when I start it, or should I be looking for another condition such as flooding?

Any Ideas?

 

[DGartzos]

Re: 1973 Johnson 65 HP, "Bogs" on accel

Healthy spark ???

After shut off, gas evaporates in warm chamber and mixture oil remains on spark plug at higher concentrations. There is always a leak current on spark plugs porcelain surface which increases with oil deposits. Now you have the problem when chambers are at max full with mixture and need a strong spark to ignite. It is possible that a weak spark will not jump the gap even on new spark plugs ...

Check leads, contacts, pipes ....
It is best to rig on a spark tester to see a strong crispy blue 1/2" spark !!!

Quick test-remedy: halve spark plug gap.

When testing spark, disconnect remote control connector to isolate and locate any trouble coming that side.

 

[Rick Thomas]

Re: 1973 Johnson 65 HP, "Bogs" on accel

Hey there bud,
Been away from the computer for a couple weeks boating. I think I fixed my issue. I blew my old prop out and replaced (has nothing to do with the similar issue). I replaced it but the wife came to me and asked if she should crack open the little vent on the cap of the 6gal tank when she primes it for me. She wasn't opening the vent at all and vapor locking the gas tank, and thus the fuel line. It would run but after a while get real doggish and have no power. The bulb wouldn't collapse (I figured it would under suction) but it doesn't, new fuel line = tough bulb. The system gets barely enough fuel flow to keep it running but you might as well have a Chihuahua pulling your sled. This helped me and all is good now.
Regards,
Rick

 

[Ironguts]

Re: 1973 Johnson 65 HP, "Bogs" on accel

I still suggest a carb rebuild kit even if the parts look ok. It's good preventative maintenance for $20 bucks even if it's not causing the problem. Float valve and seat may be worn but not apparent to the naked eye. And new gaskets will help to prevent fuel and vacuum leaks. How does your choke valve look? It should be fully open. If your mixture is too rich it will cause starting and WOT problems. Pull the plugs after WOT. If they're wet then flooding may be the problem or possibly ignition problem. Is it possible that the engine could be overheating? If you don't have a temp gauge, try a wax stick on the engine block before and after WOT to see if she's running at the right temp.