9.5 Johnson Seahorse running at 1/2 HP

L

Livingston_Duvall

Recruit
Joined
Oct 4, 2009
Messages
1
I've just bought a 12 foot livingston that had a 9.5 Johnson Seahorse (1966). The outboard starts up great with 1 pull and idles well all is good. Well all is good except that it won't get the boat up to plane and feels like I'm going at half speed.

I've been told for that boat it should skip right along the water pretty good.

I'm stumped the plugs look good, the motor is very clean and it runs well just at lower than expected HP.

Any ideas of what would be the cause of the reduction in HP? I'm thinking fuel filter and maybe a new prop would do the trick. Please Help.
 
muskrat

muskrat

Chief Petty Officer
Joined
Apr 13, 2004
Messages
445
Re: 9.5 Johnson Seahorse running at 1/2 HP

Sound like you are loosing spark on one cylinder.Run motor and pull one wire off at a time and see of theres a change.Or high speed jet clogged...
 
F

F_R

Supreme Mariner
Joined
Jul 7, 2006
Messages
28,226
Re: 9.5 Johnson Seahorse running at 1/2 HP

Livingston_Duvall said:
I've just bought a 12 foot livingston that had a 9.5 Johnson Seahorse (1966). The outboard starts up great with 1 pull and idles well all is good. Well all is good except that it won't get the boat up to plane and feels like I'm going at half speed.

I've been told for that boat it should skip right along the water pretty good.

I'm stumped the plugs look good, the motor is very clean and it runs well just at lower than expected HP.

Any ideas of what would be the cause of the reduction in HP? I'm thinking fuel filter and maybe a new prop would do the trick. Please Help.
Click to expand...

99.9% of half power problems are caused by running on one cylinder. It will run just fine on one, but have no power. Check your compression to make sure it is an ok motor internally, then fix the ignition system. It could be as simple as a bad spark plug, but if not then you have to pull the flywheel to see what's wrong.
 
kenmyfam

kenmyfam

Supreme Mariner
Joined
Aug 10, 2006
Messages
14,398
Re: 9.5 Johnson Seahorse running at 1/2 HP

Could be many things or indeed nothing at all.
What makes you think you are at half speed ?? does it plane out ??
You should do a basic health check on the motor for your own peace of mind at least.
Compression
Spark
Fuel delivery
Spark plug condition

What does "skip along pretty good" actually mean ??
Could be as simple as motor set up. Height and trim are critical as is weight distribution (loading) of the boat.
Welcome to iboats
 
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