18hp johnson rev problems

Z

zacherey

Recruit
Joined
Nov 30, 2010
Messages
2
I have been working on an 18hp johnson fd-18. When ever I have the boat in neutral the motor revs up good but when I put it in drive the motor does not rev up to about half the rpm and seems to run more like an 9.5hp then an 18hp. Please help also I have cleaned out the carb and it still runs the same.
 
T

tx1961whaler

Vice Admiral
Joined
May 31, 2008
Messages
5,197
Re: 18hp johnson rev problems

Probably more like an 9 hp. Most likely running on only one cylinder. Pull off the spark plug wires one at a time when it's running and see.
 
Z

zacherey

Recruit
Joined
Nov 30, 2010
Messages
2
Re: 18hp johnson rev problems

well it sparked when i did that. do you think it could be the fuel pump?
 
L

Lostfisher

Petty Officer 2nd Class
Joined
Nov 2, 2009
Messages
147
Re: 18hp johnson rev problems

Test the compression on both cylinders. Also give the carb a good cleaning.
 
lindy46

lindy46

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Nov 27, 2008
Messages
3,886
Re: 18hp johnson rev problems

tx1961whaler said:
Probably more like an 9 hp. Most likely running on only one cylinder. Pull off the spark plug wires one at a time when it's running and see.
Click to expand...

If it continues running with either plug wire off, then it's not an ignition problem. If it runs when you pull one wire but dies when you pull the other wire, then it's the opposite plug which isn't getting spark.
 
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