1972 6HP Johnson Bogging Down

[timpr2]

I am new to the site so I am not sure if I am posting this question at the right place. My dads old 1972 6HP Johnson runs and idles fine in the bucket and in the water it does fine until you try to go full speed and it bogs down, it takes off fine it just want plane out, I was wondering if it could be the prop and if so how can you check it(the hub).

 

[tx1961whaler]

Re: 1972 6HP Johnson Bogging Down

A slipped prop hub will not cause bogging; it will cause the opposite: an engine that races but goes no faster.

 

[AlTn]

Re: 1972 6HP Johnson Bogging Down

is it running on both cylinders?...while the engine is idleing, disconnect each sparkplug separately...if the motor dies when one is disconnected but not when the other is...that's the good cylinder...If you'll read all the info contained in the sticky post.. Top Secret Files...you can gain a lot of useful knowledge...post back when you determine that it's firing on both cylinders...if both are firing you'll normally just hear a drop in the rpm's as each plug wire is pulled

 

[timpr2]

Re: 1972 6HP Johnson Bogging Down

It only bogs down in the water and thats why I though it might be a prop but what you said, Whaler about the prop makes sense.thanks for the info on the prop. I have checked all the cylinders for compression and checked the spark with a tester had good spark on both plugs tried taking one off and then the other not hardly any change, just a little rpm drop. Not worked on many boat motors but have rebuilt and worked on alot of other engines. Thanks for the info so far.

 

[58rude]

Re: 1972 6HP Johnson Bogging Down

More than likely fuel related. Put some premix in a spray bottle and spray it in the carb when it starts bogging and see if it picks back up. You can also just try choking it when it bogs and see if it picks back up. If it does pick up, then you know you have a fuel issue.

 

[timpr2]

Re: 1972 6HP Johnson Bogging Down

I tried to pull the choke out while it was doing it and the motor went dead, but I will try some premix the next time I go out, tomorrow I hope. I read somewhere in the secret files about a vent on the tank but mine does not have one on the gas lid tank it is a fairly new tank is there another vent near the outlet line by the fuel gauge on the tank.

 

[Tim Frank]

Re: 1972 6HP Johnson Bogging Down

I am new to the site so I am not sure if I am posting this question at the right place. My dads old 1972 6HP Johnson runs and idles fine in the bucket and in the water it does fine until you try to go full speed and it bogs down, it takes off fine it just want plane out, I was wondering if it could be the prop and if so how can you check it(the hub).

Have you run this setup yourself before with better results, or are you assuming how it should perform?
Depending on the boat and your weight, it may never "plane out."
Not a lot of reserve with 6 HP.

 

[58rude]

Re: 1972 6HP Johnson Bogging Down

every tank has to have a vent

 

[jay_merrill]

Re: 1972 6HP Johnson Bogging Down

Sounds like some junk in the HS orifice. I'd say its time for a carb cleaning and rebuild.



???

 

[timpr2]

Re: 1972 6HP Johnson Bogging Down

Thanks so far, Tim I did run this setup a few years ago when it was still my dads boat and motor. It is a 10' alumacraft flatbottom with just me(approx.150lbs)and the motor and tank, and it did fine, no gear, no batteries, no seats, no trolling motor; and it ran fine. Now,it just does not want to plane out. I took the carb off and it looked new inside. Jay the HS orifice you are talking about is behind the drain plug on the bottom of the carb? It looked good. Jay I still have not located the vent on my tank? Does anybody know where my vent may be located?

 

[AlTn]

Re: 1972 6HP Johnson Bogging Down

does it have a small cap in the center of the larger fuel fill cap?...if so...that's the vent....for testing you can leave the fuel fill cap hanging if the tank isn't too full you shouldn't have too much splashing out...would advise not to smoke around this while the cap is off...you can pump the bulb while running to see if things pick up, doing this bypasses the fuel pump which might have a weak or leaking diaphram

 

[Tim Frank]

Re: 1972 6HP Johnson Bogging Down

Thanks so far, Tim I did run this setup a few years ago when it was still my dads boat and motor. It is a 10' alumacraft flatbottom with just me(approx.150lbs)and the motor and tank, and it did fine, no gear, no batteries, no seats, no trolling motor; and it ran fine. Now,it just does not want to plane out. I took the carb off and it looked new inside. Jay the HS orifice you are talking about is behind the drain plug on the bottom of the carb? It looked good. Jay I still have not located the vent on my tank? Does anybody know where my vent may be located?

Still on the simple things....any chance that someone adjusted the trim too high or low?

 

[timpr2]

Re: 1972 6HP Johnson Bogging Down

ALTN there is no small cap in the center of the fuel cap, I tried pumping the bulb when I was running and that did not help good advice on not smoking around a open fuel tank, I will try the fuel tank lid off tomorrow or the next day I hope. Tim nobody changed the trim still in the second slot. Thanks for all the advice everone.

 

[jay_merrill]

Re: 1972 6HP Johnson Bogging Down

How long has it been since the motor has been run, prior to your recent attempt?



???

 

[Willyclay]

Re: 1972 6HP Johnson Bogging Down

I tried pumping the bulb when I was running and that did not help.

Next time out, try choking the motor when it starts to bog. If it picks up, your high-speed jet is probably clogged with crud. BTDT with my 1973 Evinrude 6HP which is identical to yours.
Good luck!

 

[Tim Frank]

Re: 1972 6HP Johnson Bogging Down

Next time out, try choking the motor when it starts to bog. If it picks up, your high-speed jet is probably clogged with crud. BTDT with my 1973 Evinrude 6HP which is identical to yours.
Good luck!

According to his posts he has done that.

 

[2wings]

Re: 1972 6HP Johnson Bogging Down

Sounds like a fuel problem. Something is restricting the flow of fuel; start at the fuel tank and check all the way to the diaphragm. Old hose may appear fine but may be seriously cracked at connection points which allows air to enter line when under full throttle power.

 

[timpr2]

Re: 1972 6HP Johnson Bogging Down

Thanks for the help so far, but I took her out and tried the things that was suggested and she still did not plane out. So I guess I will look under the flywheel and see if I could see any problems there. Thanks Tim

 

[Tim Frank]

Re: 1972 6HP Johnson Bogging Down

Given that you have checked the spark and compression, I'd throw my vote in with the fuel issue folks.
If the spark is good I am not sure if there any reason at this point to pop the flywheel.

Again trying for the easy ones, see if you can get a known good tank and hose and see if that makes any difference.
That will rule out tank/hose/and bad fuel in one shot.

 

[timpr2]

Re: 1972 6HP Johnson Bogging Down

Anybody know the torque specs for the flywheel on my 1972 6HP Johnson. Any help will be appreciated. Thanks for the advice Tim