Johnson 15hp bogging down

[tdp63]

Re: Johnson 15hp bogging down

Very good. Well in that case it seems to be set right. Buggered if I know what my problems is then. The cam plate shows signs of wear. Could a worn plate cause my problems? Bit hard to describe how worn it is, but lets hypothetically assume that it is very worn.

 

[OBJ]

Re: Johnson 15hp bogging down

Is there any deep grooves in the cam roller? If so, replace it. Other than that, sounds like you have it set right. Run the throttle to WOT, motor not running with the gear case in forward gear, and look at the spring pin on the throttle plate shaft on the starboard side of the carb. It should be vertical which would mean the throttle plate is where it should be.<br /><br />Have you run it lately to see if the changes have made a difference? Low speed needle set OK?

 

[tdp63]

Re: Johnson 15hp bogging down

Ran it last night after carby rebuild- prob still there. The spring pin is NOT vertical. At about 11 o'clock. I'm starting to get excited now with actually finding something that may not be set right.

 

[tdp63]

Re: Johnson 15hp bogging down

My other motor which does not have the problem IS vertical.

 

[tdp63]

Re: Johnson 15hp bogging down

Now what do I do? Adjust the can plate till pin is verticle? Roller is in good condition. There are some small grooves along face of cam plate that can be felt with finger.

 

[tdp63]

Re: Johnson 15hp bogging down

And the roller is not as far along the cam plate at WOT as it is on the no problem motor. Not much difference but noticeable. Mmmm...

 

[mikeyzx2]

Re: Johnson 15hp bogging down

How have the plugs looked after running the motor? Do they look more oily when compared to others? I'm thinking from what OBJ has mentioned about maybe getting too much fuel that there's gotta be a sign...<br /><br />I doubt this has anything to do with it, but after troubles with my '85 8hp Seahorse, I discovered some bloak had put the fuel pump back together wrong, basically had a couple gaskets switched. It had the same symptoms you're describing. I rebuilt it and have had no problems since..........<br /><br />Mike

 

[tdp63]

Re: Johnson 15hp bogging down

G'day Mike. The plugs are coming up OK. One better than the other but within the 'OK' range. We put another 'known to be working fine' fuel pump on and no difference. I really have thrown a doozy in here haven't I. The rubbish tip is open here tomorrow morning. I should whisper that into the motors ear and see if the threat of death by scrap metal compacter will make it start playing the game!

 

[mikeyzx2]

Re: Johnson 15hp bogging down

Ask OBJ how many times he's heard from me about my stinkin' V4!!! I've fooled around with it for about a year off and on, so yours won't qualify to be a doozy yet. <br /><br />One plug looking better than the other may be a hint towards something else, it depends on how diffrent. My Seahorse as we speak blackened one plug but the other still looked fairly new, after a hour or so running. I haven't worked that out yet, gotta put it in a bucket when I got time and do some spark checking. <br /><br />Speaking of that, have ya'll took a look under the flywheel yet? I didn't realize '76 models have breaker points on them until I looked in book.

 

[OBJ]

Re: Johnson 15hp bogging down

The reason I'm looking at to much fuel is from tdp's post.....he gives it a little throttle and it will come "alive". This is the same as giving it more air to catch up to the fuel flow.....it's actually bogging down with too much fuel until the air catch's up.<br /><br />tdp....what kind of low speed needle adjustment have you got.....how many turns out?<br /><br />EDIT: Just a thought....you posted that the spark is good. That means it's jumping at least a 7/16" gap....don't know what that is in metric....question is, did you do the spark test with the spark plugs in or out of the engine?

 

[paul239]

Re: Johnson 15hp bogging down

here's 2 cents' worth....on my ancient 1960 10 horse Johnson, I found that the shaft/bellcrank that the little roller is on was bent...would never open the throttle plate all the way...I just used some pliers to make sure that the throttle plate was open all the way when the cam plate was rotated to full advance, then backed up and re-set cam plate mark on the roller as instructed farther up in this post...made quite a difference.

 

[paul239]

Re: Johnson 15hp bogging down

sorry...too quick on the button...I also had to pull the flywheel, clean and re-lube the plate that the coils are mounted on...40-some year old grease was causing it to bind, preventing the cam plate from rotating all the way to full advance...Now you have 4 cents' worth hope this helps!

 

[tdp63]

Re: Johnson 15hp bogging down

I am considering putting a bit of hose over the roller to compensate for any wear. Seen it on another one. What do you think?

 

[tdp63]

Re: Johnson 15hp bogging down

also putting a new float in carby.

 

[paul239]

Re: Johnson 15hp bogging down

I think a new float's a good idea...I dunno about the hose on the roller, though...might just make it too big...If there's no big groove in it, I'd just (carefully) bend the little arm..I could see the throttle plate on mine after removing the air intake/silencer, if I looked into the carb at just the right angle, with a good flashlight. I just looked over the linkage, and "tweaked" stuff until the throttle plate was wide open at maximum advance.

 

[tdp63]

Re: Johnson 15hp bogging down

Waiting for the float to do that first and then, if need be, have a 'tweak'. Thanks for that. I need to hear ideas.

 

[tdp63]

Re: Johnson 15hp bogging down

Okay, finally back. Replaced float and in the tank it appears that bogging down problem is solved. But I do say 'appears'. We'll see for sure when out on water. Still have an issue though. Motor is running and smoking like it is rich BUT it still gives a cough/sneeze and stalls like it is lean. Can't get it to idle well at all. Air leak? I have ordered new crank shaft seals and plan on putting top in first and see what happens. Can't see leak any where else. What do you blokes think? Am I on right track?

 

[OBJ]

Re: Johnson 15hp bogging down

How far is the low speed needle backed out from GENTLY SEATED? The starting point is about a turn and one half out.<br /><br />Is the engine warming up at idle?<br /><br />Also noticed after re-reading the thread that the engine is a 76' and would have a standard ignition system. If the points are not set correctly (.020), the engine will not idle well. Might be something to look at and also make sure the spark at each cylinder will jump at least a 7/16" gap.

 

[tdp63]

Re: Johnson 15hp bogging down

New crankshaft seal did nothing. We used the correct procedure for low speed adjustments as detailed in previously supplied links. Engine is warming up at idle. Points are set correctly. Spark jumps half an inch and is bright and zappy. However it runs like it is rich but also gives a lean sneeze. Can't get it to idle well at all.

 

[OBJ]

Re: Johnson 15hp bogging down

Well, back to the drawing board........<br /><br />OK...heres some other things....<br /><br />Connect a piece of clear tubing between the fuel pump and carb. Run the engine and watch for bubbles in the tubing. Also, pull the fuel pump away from the block and squeeze the primer bulb. Watch for any fuel coming out the hole that goes against the engine block.<br /><br />Water getting into the cylinders....don't take a whole lot. You would need to pull the head and look for "washed" places on the pistions.<br /><br />Bad reeds....if a reed(s) are bad, check for blow back through the carb....real noticable at idle. Carb will spit fuel out.<br /><br />Bad lower seal. The lower seal around the drive shaft can be bad. Hard to detect and repair. Have to pull the block to get to it......last resort thing.<br /><br />Check around the mating surfaces of the crank case for leaks. Dripple some choke and carb cleaner around the cracks. If the engine picks up rpm, there is a leak in the mating surfaces.<br /><br />I'm sure one of the other guys will jump in here and give you some ideas also.....