2001 Johnson 70 Carb mixtures

[Landon116]

Hey guys,
On my journey of debugging my johnson 70, I'm trying to figure out these carbs. Engine runs great past half throttle, but between 0 and 1/2 its jerky rough and hesitant. So naturally I started playing with the carb mixture screws. Come to find out they are 7 full turns out each, they look like they are about to fall out lol. So I had the boat tied off at the dock and started back at around 1 1/2 turns out and it wont even come close to running .. sneezing and dying. Lean right? I back them out more. I cant even get the idle to smooth out at all, I'm getting no response from the screws hardly. The only way I can get down the river is like 7 turns out, way to rich but it will sort of run.

I'm thinking about rebuilding the carbs, new filters, checking the timing and carb synchronization.

what else am I missing? The p.o removed the vro and replaced the fuel pump to non vro.

thanks guys !

 

[Joe Reeves]

I retired in 1991... 10 years before your engine was manufactured... BUT... perhaps the following which pertains to the 3 cylinder 70hp models of my day may be of some use to you (worth a shot). Are those the original carburetors... is this engine new to you?

Hopefully a fellow member can tell you exactly what size jets belong in those carburetors.

********************
(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 1: 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.

Note 2: If the engine should be a three (3) cylinder engine with three (3) carburetors, start the adjustment sequence with the center carburetor.

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.
********************

 

[flyingscott]

Has the pulse limiter been removed?

 

[Landon116]

Has the pulse limiter been removed?

I had to look up to see what this is. But I went out and looked, is it the threaded nipple in the side of the block with a hose leading to the fuel pump? If so, then no it's still there.
thanks !!

 

[racerone]

That item is not needed for a conventional pump.

 

[Landon116]

That item is not needed for a conventional pump.

Thanks racerone, but I guess the fuel pump he installed eliminated the vro but still is hooked up to the conventional fuel pump, should I plug it off and thread a plug in the pulse limiter hole?

thanks!

 

[racerone]

Well-----You need to post pictures ----I now have no idea what you have installed here.-----Or are you somehow confusing the electric primes with a " fuel pump "-----The electric primer is a valve and not a pump !

 

[Landon116]

Well-----You need to post pictures ----I now have no idea what you have installed here.-----Or are you somehow confusing the electric primes with a " fuel pump "-----The electric primer is a valve and not a pump !

The p.o removed the vro system, replaced the fuel pump mounted on the engine with a convential fuel pump.

 

[racerone]

Post #6 was not clear.-----It indicated that there were 2 pumps the way I read it.

 

[Landon116]

Post #6 was not clear.-----It indicated that there were 2 pumps the way I read it.

Sorry, I was referring to the pulse limiter. It's still hooked up as required by the new fuel pump. Sorry for the confusion. But either way, I know the engine runs well past half throttle so something is working right! I'm just gonna rebuild the carbs and try to dial them in because the way they are now, they are almost like they are completely un-tuneable.

 

[racerone]

But the PULSE LIMITER is not required by the conventional pump.-----Do you know the purpose of the pulse limiter , yes or no ?

 

[Landon116]

But the PULSE LIMITER is not required by the conventional pump.-----Do you know the purpose of the pulse limiter , yes or no ?

I'm just going on what's on the boat and how the retro fit pumps come. I didnt buy it. I didnt install it. I'm just trying to get an idea of how it should be set up.

from what I understand, The pulse limiter is in place to prevent a high pressure surge from a crankcase backfire that would in turn damage the fuel pump diaphragm. Without it I know the old engines use to blow diaphrams from backfires.
If this isn't right or I dont need it , then inform me.

 

[racerone]

But I have clearly stated that it is NOT REQUIRED !!

 

[Landon116]

But I have clearly stated that it is NOT REQUIRED !!

So I can just eliminate it and run a hose straight to it from the block?

Sorry I pissed you off haha. I was just trying to understand how it's supposed to be set up. Could this being in place cause issues with a convential pump?

 

[Landon116]

I retired in 1991... 10 years before your engine was manufactured... BUT... perhaps the following which pertains to the 3 cylinder 70hp models of my day may be of some use to you (worth a shot). Are those the original carburetors... is this engine new to you?

Hopefully a fellow member can tell you exactly what size jets belong in those carburetors.

********************
(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 1: 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.

Note 2: If the engine should be a three (3) cylinder engine with three (3) carburetors, start the adjustment sequence with the center carburetor.

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.
********************

Hey thanks for info. Yes this engine is new to me. And yes the carbs appear original.

 

[Joe Reeves]

I appreciate the reply, thank you. That tells everyone that you have no back history of it... and we go from there. Whether that pulse limiter creates a problem or not, I've no idea but it's best not to use it with a regular fuel pump.

 

[oldboat1]

You will need to change out the impeller if you haven’t done that, as running in river water (sand/silt) is hard on them. Running temps should be in the range of 120-140. (160F is too hot.)

Shortcuts in cleaning and rebuilding carbs are a mistake. Soak metal tops and bottoms in something to cut through fuel residue (I use lacquer thinner). Take the idle needles out before soaking, along with core plugs. Leave any lead plugs in place. Use soft small diameter wire to make sure there are no blockages, and after soaking, blow out every opening with carb cleaner using the plastic nozzle.

Idle air needle adjustments are very sensitive when the carbs are clean and operating properly.

 

[Landon116]

You will need to change out the impeller if you haven’t done that, as running in river water (sand/silt) is hard on them. Running temps should be in the range of 120-140. (160F is too hot.)

Shortcuts in cleaning and rebuilding carbs are a mistake. Soak metal tops and bottoms in something to cut through fuel residue (I use lacquer thinner). Take the idle needles out before soaking, along with core plugs. Leave any lead plugs in place. Use soft small diameter wire to make sure there are no blockages, and after soaking, blow out every opening with carb cleaner using the plastic nozzle.

Idle air needle adjustments are very sensitive when the carbs are clean and operating properly.

Thanks! I'm one step ahead, I went through the cooling system just a couple weeks ago, New water pump and thermostat, etc. I just took the carbs off and found that one jet/valve seat is a larger diameter than the others and was stripped out by the last guy! ( looks like he couldnt get it out and just replaced the rest of them) The right tools make the difference..but they will get a good cleaning and new parts. Plus a new nipple for the pulse limiter, I'm making headway and I will keep digging. I will update this forum for the sake of others with the same problems.

thanks fellas.
.

 

[Landon116]

I appreciate the reply, thank you. That tells everyone that you have no back history of it... and we go from there. Whether that pulse limiter creates a problem or not, I've no idea but it's best not to use it with a regular fuel pump.

I just took the carbs off and found that one jet/valve seat is a larger diameter than the others and was stripped out by the last guy! ( looks like he couldnt get it out and just replaced the rest of them) The right tools make the difference..but they will get a good cleaning and new parts. Plus a new nipple for the pulse limiter, I'm making headway and I will keep digging.

thanks !!

 

[Faztbullet]

Initial setting for carbs are 2-1/4 turns out from light seat. What is compression?