18hp Johnson Sluggish

S

Sunset Beach

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Feb 15, 2012
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I have an 18HP Johnson, 1959, FD-13R, electric start. Starts great and idles ok but when I open the throttle it is very sluggish and only slightly increases in speed. Some times then it will suddenly take off and go to full speed. Today it performed that way and was running great until I idled down to slow speed. When I tried to increase fully again it wouldn't respond! It acts as though it is running initially on one cylinder and then suddenly the 2nd cuts in.

I've checked spark on both cylinders ok. Replaced both coils,points, and condensors, synchronized per my Seloc manual. One thing I noticed when synchronizing was the throttle plate doesn't completely open as though the cam travel isn't sufficient to completely open the throttle. Any ideas?

Puzzled
 
64osby

64osby

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Jul 28, 2009
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Re: 18hp Johnson Sluggish

Post a picture of the max cam travel, so we can see it.

You may want to peak in the flywheel inspection plate to see if there is worn wire that might be grounding out sometimes.

My other thought is carb, junk in the high speed or fuel pump is getting weak(or is this a pressure tank).
 
HighTrim

HighTrim

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Jun 21, 2007
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10,486
Re: 18hp Johnson Sluggish

If you are trying to do this in neutral, then yeah, it is limitied until shifted into gear.

Regarding your other issue, start with a carb rebuild.
 
kfa4303

kfa4303

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Re: 18hp Johnson Sluggish

Ditto. The revs are limited in Neutral fro safety reasons, but that motor should be a real screamer on the open water, but if it's still sluggish I'm thinking you may be dropping a cylinder. I noticed you didn't mention changing the s'plug wires. There's no sense fixing the ignition to make a nice hot spark, if the wires can't deliver it properly. Not to worry, lots of folks overlook this part of the job. You'll need to get 7mm copper core spark plug wires and a couple new boots. I've had luck getting both at NAPA and/or Carquest, but you may have to do some looking. You can also try snipping off about 1/2" from each of the old wires at the coil end to see if you can expose some fresh copper. You'll then need to twist the wire onto the coil post, rather than just jamming them on there as so many people mistakenly do. Here's a handy link that can walk you through a tune up from top to bottom. The key is to be systematic and methodical. I usually work from the top down, checking off jobs along the way. Keep us posted. Holler if you get stuck.

http://www.duckworksmagazine.com/06/columns/max/index6.htm
 
S

Sunset Beach

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Feb 15, 2012
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Re: 18hp Johnson Sluggish

kfa4303 said:
Ditto. The revs are limited in Neutral fro safety reasons, but that motor should be a real screamer on the open water, but if it's still sluggish I'm thinking you may be dropping a cylinder. I noticed you didn't mention changing the s'plug wires. There's no sense fixing the ignition to make a nice hot spark, if the wires can't deliver it properly. Not to worry, lots of folks overlook this part of the job. You'll need to get 7mm copper core spark plug wires and a couple new boots. I've had luck getting both at NAPA and/or Carquest, but you may have to do some looking. You can also try snipping off about 1/2" from each of the old wires at the coil end to see if you can expose some fresh copper. You'll then need to twist the wire onto the coil post, rather than just jamming them on there as so many people mistakenly do. Here's a handy link that can walk you through a tune up from top to bottom. The key is to be systematic and methodical. I usually work from the top down, checking off jobs along the way. Keep us posted. Holler if you get stuck.

Sunset Beach here:

Finally got my new spark plug wires and tore down the magneto to replace them. Also found that one of the originals had only been stuck in instead of twisting into the coil (I didn't tear the armature plate down completely the first time when I replaced the coils!).

Anyway the motor does scream now when I want it to!

Thanks to all for the advise and links to helpful contacts.

Sunset Beach

PS: what does the R stand for in the FD-13R model number?
SB
Click to expand...
 
kfa4303

kfa4303

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Re: 18hp Johnson Sluggish

Sweet! Glad you got her running again. The letters after the number are usually just production batch numbers and don't really mean anything. However, if when/you see a letter before the hyphen it is significant. It's usually an "E" for electric start and/or and "L" for longshaft. So an electric start, longshaft 1966, 33 hp would be an RXEL-14D (again the last letter after the numbers are generally insignificant). Happy boating. Vroom-vroom!
 
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