Loss of Power??

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bkatz

Seaman Apprentice
Joined
Mar 5, 2009
Messages
38
I have a 1968 20HP Johnson on a 13? inflatable. I took the Boat out the other day and it started out great, got right up on plane and all was well. About 10min in the engine sounded the same but the boat just slowed down and wouldn?t get back up to speed. At one point it started to speed up but then bogged right back down. Then when I started to go back in after the engine was off it started great again right up on plane and the same thing happened again. Any insight???? I am a newbie owner
 
bankerjohn

bankerjohn

Chief Petty Officer
Joined
Mar 21, 2008
Messages
444
Re: Loss of Power??

Best guess ... not getting enough fuel. By chance, did you try pumping the primer bulb after it slowed down?

Have you ever had the carb rebuilt? Fuel pump checked for proper operation?
 
B

bkatz

Seaman Apprentice
Joined
Mar 5, 2009
Messages
38
Re: Loss of Power??

I did try and pump the bulb, but nothing happened. The Carb was rebult. I just don't even know where to start? I also tryed the choke but everything seemed normal.
 
bankerjohn

bankerjohn

Chief Petty Officer
Joined
Mar 21, 2008
Messages
444
Re: Loss of Power??

My next guess (and that's all it is) would be overheating ... have you had the water pump rebuilt? Thermostat replaced? Does your motor have a "tell tale"? If it does, have you been seeing a solid stream of water coming out?

I'd start off with the basics ... try to eliminate what's NOT a problem first.

Do a compression test on all cylinders ... should be within 10% of each other.
Do a spark test on all plugs ... should get a bright blue 1/4"+ spark.
Check the filter screen in the fuel pump.
Etc.
 
F

film495

Petty Officer 2nd Class
Joined
Apr 8, 2009
Messages
149
Re: Loss of Power??

take the plugs out and check the gaps, make sure the wires are connected properly, see if one of the plugs is wet or black with carbon, you may be dropping fire on one cylinder and it will run OK like that, just no power. Also, you can run the motor and check with your finger (carefully) to see if one base near the plugs is not and the other not, you could just have one fouled out plug that keeps dropping a cylinder; an easy fix if it is just a plug really.
 
kenmyfam

kenmyfam

Supreme Mariner
Joined
Aug 10, 2006
Messages
14,385
Re: Loss of Power??

Compression and spark check. Could be a coil starting to give out when the motor get's hot.
 
B

bkatz

Seaman Apprentice
Joined
Mar 5, 2009
Messages
38
Re: Loss of Power??

Thanks for the guidance. I will check and keep everyone posted!
 
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