Can't get a good RPM to get a decent speed

[BigB9000]

boat/engine in question is a 1967 holms, 15' flat bottom, bearing a 115hp johnson outboard.

Took the boat for a test run.

at idle/little throttle it puts around the lake just fine. but when you give it more lever (or speed/gas)

It'll increse speed mabye 5-10 mph, and probably cant pass 2,000RPM (no tahc)

and not enough speed to get onto a plane

out of the water it'll rev up just fine.

took the covers off a looked down the carbs, I have a good stream of fuel going down the carbs, so i dont think its a fuel isue.

also, 30 minutes of idling will suck up 3 gallons of gas. this normal?


any ideas?

work done:
water pump
lower unit oil
carbs rebuilt
new battery
new spark plugs
new fuel pump
new fuel lines
new tank

 

[CharlieB]

Re: Can get a good RPM to get a decent speed

Re: Can get a good RPM to get a decent speed

Is one or two spark plugs 'clean' but wet and the others somewhat blackened?

You may have a weak spark or NO spark on the clean plugs.

Test spark intensity.

 

[bennysku]

Re: Can get a good RPM to get a decent speed

Re: Can get a good RPM to get a decent speed

I had a similar issue and i resolved this by adjusting the spark advancement. After increasing the spark advance at lower speeds (in small increments) i was getting higher rmp's coming out of the hole allowing me to then go above 2500rpm at wide open. Before the adjustment it seemed boogged down, but never did die or backfire.

 

[BigB9000]

Re: Can get a good RPM to get a decent speed

Re: Can get a good RPM to get a decent speed

I played around with it, not much of a change. if i put the adjust all the way in, it wont pass idle, with the screw a tad out, its the same as all the way out

 

[tashasdaddy]

Re: Can get a good RPM to get a decent speed

Re: Can get a good RPM to get a decent speed

(Carburetor Adjustment - Single S/S Adjustable Needle Valve)
(J. Reeves)

Initial setting is: Slow speed = seat gently, then open 1-1/2 turns.

Start engine and set the rpms to where it just stays running. In segments of 1/8 turns, start to turn the S/S needle valve in. Wait a few seconds for the engine to respond. As you turn the valve in, the rpms will increase. Lower the rpms again to where the engine will just stay running.

Eventually you'll hit the point where the engine wants to die out or it will spit back (sounds like a mild backfire). At that point, back out the valve 1/4 turn. Within that 1/4 turn, you'll find the smoothest slow speed setting.

Note: As a final double check setting of the slow speed valve(s), if the engine has more than one carburetor, do not attempt to gradually adjust all of the valves/carburetors at the same time. Do one at a time until you hit the above response (die out or spit back), then go on to the next valve/carburetor. It may be necessary to back out "all" of the slow speed adjustable needle valves 1/8 turn before doing this final adjustment due to the fact that one of the valves might be initially set ever so slightly lean.

When you have finished the above adjustment, you will have no reason to move them again unless the carburetor fouls/gums up from sitting, in which case you would be required to remove, clean, and rebuild the carburetor anyway.

 

[BigB9000]

Re: Can get a good RPM to get a decent speed

Re: Can get a good RPM to get a decent speed

there is no needle valve.

nothing adjuatable at all in there

 

[kenmyfam]

Re: Can get a good RPM to get a decent speed

Re: Can get a good RPM to get a decent speed

there is no needle valve.

nothing adjuatable at all in there

???? Look again !!!

 

[ezeke]

Re: Can get a good RPM to get a decent speed

Re: Can get a good RPM to get a decent speed

What is he to look for? There are no adjustments on a 1977 115 carburetors, they are all four fixed jets on each carburetor.


Unless you had the ignition apart, you should not be adjusting the timing. If you do adjust it, do it by Mr. Reeves method exactly (unless you have a test wheel and test tank).

This thread will help, the timing is the same as yours: http://forums.iboats.com/showthread...E:+If+your+engine+has+the+Fast+Start+feature,

 

[BigB9000]

Re: Can get a good RPM to get a decent speed

Re: Can get a good RPM to get a decent speed

Maybe im just crazy but "set the timing at 24?"

Im still trying to figure out how to set the timing.

move the timer base, thus disconnecting the linkage to it?

Im just not getting it

 

[BigB9000]

Re: Can get a good RPM to get a decent speed

Re: Can get a good RPM to get a decent speed

Took some pics, I haven't resized them yet, so I don't want to flood the thread with pics, so here a links:

linkage in neutral:

http://gi69.photobucket.com/groups/i54/6J3SYMPVT3/nuteral.jpg

Full throttle:

http://gi69.photobucket.com/groups/i54/6J3SYMPVT3/fult.jpg

interesting part is the spark plugs

the left side side is nice and BLACk, the right side looks normal (both sets of plugs)

http://gi69.photobucket.com/groups/i54/6J3SYMPVT3/plugslr.jpg

both left pugs: (the cleaner parts is where I touched them)

http://gi69.photobucket.com/groups/i54/6J3SYMPVT3/plugsr.jpg

looks like a problem on the left bank no?