Problem with my 8hp getting power

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swfl mike

Seaman Apprentice
Joined
Nov 23, 2009
Messages
46
Hi, I have an '88 Johnson 8hp that was given to me that I'm trying to get going. To start with I changed the plugs, rebuilt the fuel pump, replaced the fuel lines, and cleaned the carb.

When it's on a stand in a test bucket I can fire it up and it sounds great and will rev up just fine. But when I put it on the jon boat and put it in gear it gets bogged down, the more throttle that I give it the crappier it runs. I tried adjusting the screw on the carb and it doesn't really help much wherever it's at.

Where should I go from this point? Thanks for any advice,



Mike
 
E

ezeke

Supreme Mariner
Joined
Sep 19, 2003
Messages
12,532
Re: Problem with my 8hp getting power

Compression test, then spark test; you are very probably only running on one cylinder.
 
S

swfl mike

Seaman Apprentice
Joined
Nov 23, 2009
Messages
46
Re: Problem with my 8hp getting power

For the compression test do I need to have a gauge or can I just put my thumb over the whole and pull the chord to see if it has anything?
 
S

swfl mike

Seaman Apprentice
Joined
Nov 23, 2009
Messages
46
Re: Problem with my 8hp getting power

Alright finally got around to playin around with the motor. I pulled each plug individually and put my thumb over the holes while someone pulled the chord and both times it blew my thumb off the hole. Also checked spark and had spark on both plugs.

Do I need to do a ligitimate compression check or is that method good enough?

Where do I go from here?
 
psteurer

psteurer

Petty Officer 1st Class
Joined
Nov 10, 2008
Messages
366
Re: Problem with my 8hp getting power

Compression is real important. You may be able to go to an auto parts store and borrow a compression gauge. What is important is that the compression on each of your 2 cylinders is within 10% of each other.

Just reading your first post, you say you are idling okay and have problems when you increase the throttle. You could have a clog in the high speed jet of the carburetor. When you cleaned the carburetor did you use you remove the needle valves and thoroughly clean everything?
 
S

swfl mike

Seaman Apprentice
Joined
Nov 23, 2009
Messages
46
Re: Problem with my 8hp getting power

Yeah I think I did a pretty good job on the carb cleaning. I soaked in carb cleaner for about 2 hours than washed it out with water and sprayed it with an air compressor. I removed all the removable parts from it and made sure everything was as clean as could be, it didn't really look all that bad to begin with.

I'll call around and see if I can get my hands on a compression checker.
 
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