CLAMJACK61
Cadet
- Joined
- May 18, 2010
- Messages
- 8
This is about a 1964 or 1965 model Johnson. It has the fixed HIGH SPEED (non-adjustable) needle in the carburetor. The motor will not stay running for long at idle, nor will it idle as low as it should. At mid to high speed the cylinder head gets way too hot, over 163* (I used a 163* Thermomelt stick & it melted).
It also begins to make a sound from the crankcase/cylinder area that sounds very much like pre-ignition. I installed; Brand new ignition coils, new spark plug wires, new points (Set EXACTLY .20) condensers & spark plugs. I re-built the carbeurator, soaked it in cleaner & blew al the passages out with compressed air, used a new kit with new float.
I pulled the cylinder head, blew air through all the water passages, even though they were clean (fresh water run motor) I removed the powerhead & made sure all the passages were unobstructed, water tube clear, etc. I surfaced the head & installed with a new gasket. I also cleaned all the carbon build up from piston domes & cylinder head (there wasn't very much).
I installed a brand new water pump impeller, the housing was in very good shape, so I re-used it. I used 89 octane fuel with Quicksilver two stroke oil at 50:1 (actually, more like 40:1, since I added a little extra due to age of motor). I thought it may be the poor quality fuel ( 10% ethanol) because it doesn't even smell like gasoline, more like stale kerosene & alcohol, but, I did pump it fresh. I bought octane boost & added it in hopes it would boost the fuel performance more similar to what it was in the 1960's. No change.
I then tried another carburetor that I simply cleaned with a spray can (carb was VERY clean already) with no change. So, I puled ANOTHER 3 H.P Johnson from the stock pile, oh, BTW, BOTH of these motors have 90 PSI on BOTH cylinders, which is good? for this age motor. Being even on both cylinders is important, and they are. I swapped out carburetors, but, installed different (but brand new) ignition coils and breaker point assemblies on this motor.
This one was a bit older, about a 1957-58 model. I tested the plug wires with my ohm meter, both were fine, so I left them on. I exchanged the water pump impeller & put her in the test tank. (BTW, I have a professional size test tank, for motors up to 50-60 H.P., so, there is no issue with running the motor & not getting enough water to the pump).
This motor ran just as badly, made the same pr-ignition noise, which starts a couple minutes after the motor is running. The cylinder head got just as hot, and, like the first motor, the side of the block where the cylinders are doesn't get hot at all, but, after running for 20 to thirty minutes it begins to get very hot on the sides as well. I tore the first motor down (1964 model) almost all the way (I didn't want to pull the crankcase in half & remove the pistons until I could have all the new parts to re-assemble it) and couldn't see anything that would cause any issue like this.
The crankshaft has no excessive movement up, down or sideways. The pistons fit well, no apparent slop best I can tell without pulling them completely out. I do see that the upper piston has minor damage to the skirt, BEHIND the rings, just one spot, where it is scored. Probably from getting hot. The cylinder wall was not damaged, at least where it's visible. The cylinders are in excellent condition. I intend to order two new pistons, rings & everything else and rebuild it.
BEFORE I do that, I need to determine WHY I am having this problem. I have the older 3 H.P. to use as my "guinea pig" to figure this out. My next plan of action is to find a marina that sells ethanol-free fuel & buy a few gallons and try that.
So, anybody have any idea as to what the problem may be? It seems to me that it's running WAY too lean, but after two different carburetors, the only thing I can figure is I am getting fuel that has WAY more ethanol than 10% in it from the local stations. Remember, this fuel doesn't even have a gasoline smell to it, like I said above, it smells more like stale kerosene & alcohol.
I forgot to mention, that it seems that when I advance the throttle lever to full WOT, it sounds like it's only running about 3/4 and not full....I am really stuck on this one.
It also begins to make a sound from the crankcase/cylinder area that sounds very much like pre-ignition. I installed; Brand new ignition coils, new spark plug wires, new points (Set EXACTLY .20) condensers & spark plugs. I re-built the carbeurator, soaked it in cleaner & blew al the passages out with compressed air, used a new kit with new float.
I pulled the cylinder head, blew air through all the water passages, even though they were clean (fresh water run motor) I removed the powerhead & made sure all the passages were unobstructed, water tube clear, etc. I surfaced the head & installed with a new gasket. I also cleaned all the carbon build up from piston domes & cylinder head (there wasn't very much).
I installed a brand new water pump impeller, the housing was in very good shape, so I re-used it. I used 89 octane fuel with Quicksilver two stroke oil at 50:1 (actually, more like 40:1, since I added a little extra due to age of motor). I thought it may be the poor quality fuel ( 10% ethanol) because it doesn't even smell like gasoline, more like stale kerosene & alcohol, but, I did pump it fresh. I bought octane boost & added it in hopes it would boost the fuel performance more similar to what it was in the 1960's. No change.
I then tried another carburetor that I simply cleaned with a spray can (carb was VERY clean already) with no change. So, I puled ANOTHER 3 H.P Johnson from the stock pile, oh, BTW, BOTH of these motors have 90 PSI on BOTH cylinders, which is good? for this age motor. Being even on both cylinders is important, and they are. I swapped out carburetors, but, installed different (but brand new) ignition coils and breaker point assemblies on this motor.
This one was a bit older, about a 1957-58 model. I tested the plug wires with my ohm meter, both were fine, so I left them on. I exchanged the water pump impeller & put her in the test tank. (BTW, I have a professional size test tank, for motors up to 50-60 H.P., so, there is no issue with running the motor & not getting enough water to the pump).
This motor ran just as badly, made the same pr-ignition noise, which starts a couple minutes after the motor is running. The cylinder head got just as hot, and, like the first motor, the side of the block where the cylinders are doesn't get hot at all, but, after running for 20 to thirty minutes it begins to get very hot on the sides as well. I tore the first motor down (1964 model) almost all the way (I didn't want to pull the crankcase in half & remove the pistons until I could have all the new parts to re-assemble it) and couldn't see anything that would cause any issue like this.
The crankshaft has no excessive movement up, down or sideways. The pistons fit well, no apparent slop best I can tell without pulling them completely out. I do see that the upper piston has minor damage to the skirt, BEHIND the rings, just one spot, where it is scored. Probably from getting hot. The cylinder wall was not damaged, at least where it's visible. The cylinders are in excellent condition. I intend to order two new pistons, rings & everything else and rebuild it.
BEFORE I do that, I need to determine WHY I am having this problem. I have the older 3 H.P. to use as my "guinea pig" to figure this out. My next plan of action is to find a marina that sells ethanol-free fuel & buy a few gallons and try that.
So, anybody have any idea as to what the problem may be? It seems to me that it's running WAY too lean, but after two different carburetors, the only thing I can figure is I am getting fuel that has WAY more ethanol than 10% in it from the local stations. Remember, this fuel doesn't even have a gasoline smell to it, like I said above, it smells more like stale kerosene & alcohol.
I forgot to mention, that it seems that when I advance the throttle lever to full WOT, it sounds like it's only running about 3/4 and not full....I am really stuck on this one.
