70hp johnson outboard WOT bogging

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Saltykris

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I have an 81 johnson seahorse 70hp outboard that I just cannot seem to get running right. Starts great, primer is working, spark tested a 3 cylinders (great spark), compression tested all 3 (145 on top, 142 middle, 142 bottom), new fuel, new fuel lines and bulb. Out of the hole no problems after that once it reaches WOT it starts to bogg down and kinda up and down after that. Runs great at half/three quarter throttle except some bogging if it hit a wave (seems to loose a little power). Also changed power pack. Thinking maybe high speed jets, carb issue? Any other suggestions
 

racerone

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Re: 70hp johnson outboard WOT bogging

Start with fuel supply.--Does it run better when you operate the manual pump ?--Start with the pick-up tube in the tank.---Install fuel pump repair kit
 

Saltykris

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Re: 70hp johnson outboard WOT bogging

Pumping the ball while running did not help at all, I saw mention of pushing the primer in to see if it picks up (have not tried this yet). Checked the tank pick up for junk or cracks and found nothing. Is their a way to test the fuel pump or should I just rebuild it anyways?
 

racerone

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Re: 70hp johnson outboard WOT bogging

If operating the fuel pump did not help then motor fuel pump is OK-------look for dirt in lines between pump and carburetor float valves.---Check high speed jets.
 

Saltykris

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Re: 70hp johnson outboard WOT bogging

Will do, I will repost any finding. On a side note I did pull the carbs a few weeks ago while putting my motor no a new hull I bought and "cleaned" them (and by that I mean took them apart and sprayed them out) it was my first time doing it so I probably missed a few things. Anyways, did take it out and run it and it ran great for about 30 to 40 minutes, than same problem again. Just thought this could be helpful is diagnosing.
 

Saltykris

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Re: 70hp johnson outboard WOT bogging

So I believe I found the reason for the bog down at WOT. I pulled the carbs last Saturday and cleaned every square inch of them, making sure all gaskets were in good shape and paying close attention to the jets. Replaced all parts Sunday and decided to test run it. Ran great, no bog, good take off. Put about 17 miles on with no issues, but of course it needs to be retested this weekend. Thanks for the advice.
 

KevinHennessey

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I have a Johnson 85 hp seahorse 1976 that hasn't ran in 8 years. I fired it up with no problem and took it for a test drive. Worked great for 15 minutes then bogged down to pretty much a crawl. It didn't stall but wouldn't accelerate. Will a rebuild of the carb and gaskets fix this problem? I'm new to boating and would love to think this problem may be just a carb and fuel issue. Any suggestions ?
 

KevinHennessey

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I have a Johnson 85 hp seahorse 1976 that hasn't ran in 8 years. I fired it up with no problem and took it for a test drive. Worked great for 15 minutes then bogged down to pretty much a crawl. It didn't stall but wouldn't accelerate. Will a rebuild of the carb and gaskets fix this problem? I'm new to boating and would love to think this problem may be just a carb and fuel issue. Any suggestions ?
 

Saltykris

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First I would start with new fuel (you probably already did but just to cover the bases) check all lines for leaks along with the pickup in the tank, air leaks will cause this also. if you put it in neutral and let it sit for a while would it run good again for a little bit? If so it's probably burning the fuel from the carbs and than having a lack of fuel staving it and making it return to idle. While running try pumping the ball, if it runs good than its fuel pump if not you can cross that off. Also try hitting the prime button when it starts to bog if it cures the problem then it's probably the carbs. I believe the high speed jets in your motor are permanent so clean them very well along with low speed jets and all nooks and crannies. New gaskets and you should be good. Did you battery charge while running? If you notice your battery dying after running than it could be stater but that's the last thing I would check....sounds like fuel issue
 

KD5EXP

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Aug 29, 2017
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Is this the same motor you have had on this boat. I should ask if it ran good on this setup before. I went through this with a 70 hp Johnson on my pontoon boat. Tried the same things. Put a different prop on and it came alive. Went from a 13 1/4 by 17 to a 14 by 11 and it jumps out of the hole and gets the rpms where they need to be.
 
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