70 hp Johnson doesn't want to go full speed

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lizard_schultz

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Joined
Jul 3, 2007
Messages
1
We just bought a used 70 hp and had it put on our boat. The fuel line was new last summer and we used fresh tanks of gas. It ran fine when the shop bucket-tested it but when we got out on the water it wouldn't go when we put the hammer down. It just bogged down but didn't stop. It eventually went at a good speed so we figured it just needed to warm up a bit (and my husband had the gas tank vent closed at first). But on the way home it went well early on and then bogged down and we could just putter along back to the dock. Any ideas on what could be wrong? Thanks!
 
tashasdaddy

tashasdaddy

Honorary Moderator Emeritus
Joined
Nov 11, 2005
Messages
51,019
Re: 70 hp Johnson doesn't want to go full speed

how long had the engine sat before you got it and started running it. what have you done to trouble shoot the problem. history on the motor. what year 70 hp. i've got a lot of ideas. got to narrow them down.. have you check compression, did it have a good strong pee stream. have you checked spark.
 
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benn6767

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Apr 11, 2009
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Re: 70 hp Johnson doesn't want to go full speed

I've got a 70 horse johnson that did the same thing, It turned out to be the prop, I put a new prop on it and problem was solved.
 
T

tx1961whaler

Vice Admiral
Joined
May 31, 2008
Messages
5,197
Re: 70 hp Johnson doesn't want to go full speed

benn6767 said:
I've got a 70 horse johnson that did the same thing, It turned out to be the prop, I put a new prop on it and problem was solved.
Click to expand...

Welcome to iboats!
Keep an eye on the post dates benn, this one was in 2007. THey probably have it fixed by now.. :)
 
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