having trouble with the low needle setup on my '55 15hp

[Philip_G]

I rebuilt my carb a few months ago and finally got out on the lake to get the motor set up, the high set up just beautifully, piece of cake.

Ran the boat around at WOT to get the engine nice and warm, set the low needle to about 2 turns out and slowed it down to idle, the problem is adjusting the low really doesn't make too much difference, I can screw it in most of the way and get the motor to sneeze, but I can't get it set to a point where it'll idle at trolling speed as smooth as I think it can, it still sputters a little.

My other problem is the motor runs differently hot and cold, it pumps plenty of water, but at wide open I can tell the motor runs warmer than at troll speed, I'd say the discharge is maybe 80 degrees, at lower speed the discharge is basically lake temp (about 55 today) so when you first slow down it runs quite a bit worse than it does after several minutes, I assume this is because it was adjusted on a cold engine, I guess it's not a big deal but it's a little annoying to have to restart it a couple times when you're trying to fish.

Anyone have any tricks for tweaking it a little? I was going by the secret file write up.

The motor did not run any better pre-rebuild, the coils are new, the plugs are new, the wires are old, but spark is very strong with a spark tester, better than 1/4", compression is low 100's

 

[F_R]

Re: having trouble with the low needle setup on my '55 15hp

My other problem is the motor runs differently hot and cold, it pumps plenty of water, but at wide open I can tell the motor runs warmer than at troll speed, I'd say the discharge is maybe 80 degrees, at lower speed the discharge is basically lake temp (about 55 today) so when you first slow down it runs quite a bit worse than it does after several minutes, I assume this is because it was adjusted on a cold engine, I guess it's not a big deal but it's a little annoying to have to restart it a couple times when you're trying to fish.

And THAT is why they put thermostats on newer motors ('59-up). And people still take the 'stat out and throw it away. If it wasn't needed, it wouldn't be in there. As you just proved.

 

[samo_ott]

Re: having trouble with the low needle setup on my '55 15hp

Usually I find that if either needle does little then that circuit has not been cleaned as well as it should and it need to be cleaned again. For the low speed did you remove the welsh plug up top and clean all the 'lil passages? Did you get all the old packing nut out of the low speed needle hole? (that's tricky)

 

[Philip_G]

Re: having trouble with the low needle setup on my '55 15hp

And THAT is why they put thermostats on newer motors ('59-up). And people still take the 'stat out and throw it away. If it wasn't needed, it wouldn't be in there. As you just proved.

yeah, never thought of that. Too bad there's no easy way to just plumb one in, guess just wait until the water warms up, hah.

 

[Philip_G]

Re: having trouble with the low needle setup on my '55 15hp

Usually I find that if either needle does little then that circuit has not been cleaned as well as it should and it need to be cleaned again. For the low speed did you remove the welsh plug up top and clean all the 'lil passages? Did you get all the old packing nut out of the low speed needle hole? (that's tricky)

yep, all that was cleaned out and the carb soaked in cleaner overnight. I guess I could always pull the needle and blow some compressed air through but I doubt that would help.

The other part of the problem is the splines on the low adjustment needle are getting worn and the knob slips, so sometimes you think you went 1/8th of a turn but you didn't move the needle at all.