Johnson 3hp?

[Vern H]

Hi folks,
I have another one. Johnson, Mod. HD25, Ser. No. 606486, Three horse I think. Has to be late 40`s or early 50`s. It runs but needs a little tweeking.
The only water discharge (pee hole) I see is right at the pivot at the transom clamp. Should there be something else? Thanks, VH

 

[Daviet]

Re: Johnson 3hp?

I am not sure about the water discharge but by the model number,HD-25 is a 2.5 hp made in 1946-1950.

 

[F_R]

Re: Johnson 3hp?

I am not sure about the water discharge but by the model number,HD-25 is a 2.5 hp made in 1946-1950.

Just a bit of spray out the exhaust relief holes is all there is. Due to the way the carburetor is intregal with the exhaust manifold on that motor, if it runs hot the gas will boil in the carburetor and it will quit running. Now, how's that for an automatic cut-off, huh?

EDIT: The serial number 606486 narrows it down to a 1947, 2.5hp

 

[Vern H]

Re: Johnson 3hp?

Daviet & FR,
Thanks for the quick responses. This one belongs to my BIL so I will have something to tell him when he comes around. It`s pretty raggedy but should make a good kicker. Be cool, VH

 

[Vern H]

Re: Johnson 3hp?

Re: 1947 2 1/2 hp Johnson,
On the back/bottom of the crankcase cover there is a chicken foot shaped fitting with a needle valve hanging out of one lower leg. Open or closed it doesn`t seem to effect much. What is it? Thanks, VH

 

[F_R]

Re: Johnson 3hp?

Re: 1947 2 1/2 hp Johnson,
On the back/bottom of the crankcase cover there is a chicken foot shaped fitting with a needle valve hanging out of one lower leg. Open or closed it doesn`t seem to effect much. What is it? Thanks, VH

In effect, that motor has two intake systems. For high speed operation, a carburetor on the side admits fuel and air through a 3rd port cylinder arrangement. For idle speed operation, air and fuel is admitted by that port on the front that you describe. That mixture goes in through a rotary valve. The wheel on the tank adjusts the high speed mixture and the needle on the front adjusts the idle mixture. Thre is some interaction between the two, so it takes a bit of finesse (fiddleing) to get them right.

The idle needle is very sensitive. If it is off just a wee bit, it is way off. Begin with it open 5/8 turn. Start the motor (on a boat in the water) and adjust the tank wheel for best running at full throttle. Then slow down to idle and very carefully tweak the idle needle for best idle. Barely turning it makes a difference between idle and quit. Repeat the whole thing till you get it right. Hey, it is an antique and they took some patience. Option: If you don't enjoy messing with it, get a newer motor.

 

[Vern H]

Re: Johnson 3hp?

F R,
I see why you rate your title, and I wouldn`t even dream of giving up tinkering with old outboards. The new ones just don`t even smell the same.
You pegged this dead right. Starts and runs but won`t idle. I fiddled with the adjustment but was not too delicate with it. I`ll give it the test! I have a 47
5hp with the same setup that I may tweek on a little bit also.
Thank you, VH

 

[Vern H]

Re: Johnson 3hp?

Testing

 

[Vern H]

Re: Johnson 3hp?

Back again. Still won`t idle after R&R and clean up of carb. and idle plumbing. Check valve and small screen were dirty but cleaned up nice. Priming pump works. Flamethrower spark in all throttle settings. Starts and runs easily with throttle a little past half. Below half and it dies. the idle adjustment has no effect. I test ran the 47 5hp and the idle adjustment works as described. I guess I`m stumped until the next infusion of wisdom.
Thanks, VH