1988 70 hp Johnson bogging down

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dctaz37

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Apr 23, 2006
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I think this is the right year but not certain. The model is J70TLCCA. Can someone let me know how to verify the year? The problem I am having is that when I give it more than 50% throttle it bogs down. When I let off it goes again it idles and trolls fine. I read several posts and here is what I have tried. Changed the primer bulb and hoses, checked for fuel leaks, changed plugs, drained carbs, tried different tank, drained fuel filter, opened fuel pump and removed small piece of something. No luck. The bulb stays hard. The last time I was out I had my son squeeze the bulb and he said it stayed hard and he was squeezed very hard and when he did that the boat ran fine, as soon as he stopped it bogged. I was going to clean the carbs but after this discovery I'm thinking maybe the fuel pump. Please let me know what you think
 
S

Sea-Bear

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Re: 1988 70 hp Johnson bogging down

If it runs fine by squeezing the primer bulb, then you have a fuel delivery problem. I would rebuild the fuel pump if has been a while. Then if that doesn't work, I would move on to the carbs. Might be a sticky float needle keeping the bowl from filling quickly enough. I have the same problem right now. Rebuilt my pump, which is easy enough. Didn't help, so now I'm planning to clean and sync the carbs. Good Luck!
 
phillnjack2

phillnjack2

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Apr 30, 2011
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Re: 1988 70 hp Johnson bogging down

it could still be the carbs dirty.
By squeezing the bulb extra hard your helping the pressure of fuel to the carb bowls.

now also before going mad and stripping it all down, there is a little black 3 way bit of plastic pipe they call a manifold that sends the juice off in 4 directions, give this a good blow out as sometimes these can get clogged up as well.

i bet the engine was running fine last year, now youve got it out and the trouble has started.
probably fuel left in the carbs and gone manky and varnished up a few jets and holes.
its best to completely drain the carbs at end of season. i drain mine after every use to be honest.

but try the pipe then go for the carbs and the pump, they probably all need a clean anyway,or you would of stated you had cleaned
or re-built them !!!!

phill
 
D

dctaz37

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Re: 1988 70 hp Johnson bogging down

I've drained the carbs every year and have had the boat since 93. I usually don't go very fast fishing so I have never experienced a problem. One additional think I tried was choking it and that made no difference. What about how to make sure the motor is the right year? Any links in Canada to purchase a fuel pump kit?
 
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fishfeatures

Senior Chief Petty Officer
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Re: 1988 70 hp Johnson bogging down

you can purchase fuel pump kits here on Iboats.
 
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dctaz37

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Apr 23, 2006
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Re: 1988 70 hp Johnson bogging down

Does anybody have the part number? I searched my model and no luck.
 
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fishfeatures

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Mar 29, 2011
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Re: 1988 70 hp Johnson bogging down

are you still using the VRO (auto mix) or regular fuel pump ( you premix the oil into the tank)??
 
D

dctaz37

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Re: 1988 70 hp Johnson bogging down

I mix the fuel so no VRO pump. I was told way back that was a fail point.
 
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dctaz37

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Re: 1988 70 hp Johnson bogging down

Maybe I'll take a picture or get the number off the pump. Can you post picts here?
 
D

dctaz37

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Re: 1988 70 hp Johnson bogging down

boat carb.jpg
I think I attached a picture that looks like my fuel pump. Please confirm the kit you suggested is similar.
 
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fishfeatures

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Mar 29, 2011
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Re: 1988 70 hp Johnson bogging down

look at the fuel pump and try and get a number from it, that will def help. Your pump should have 3 hoses going in and out of it , the attachment only has 2.
 
D

dctaz37

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Apr 23, 2006
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Re: 1988 70 hp Johnson bogging down

Okay I think the part number is 438559 says from Mexico. Now a new pump with shipping is around $100. Is it hard to rebuild and how reliable is the rebuild vs new? Please let me know.
 
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fishfeatures

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Mar 29, 2011
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Re: 1988 70 hp Johnson bogging down

OMC part number 393103 or Sierra part # 18-7820 will def do the job for that pump.

parts for rebuild are here in iboats for $12.99
Fuel Pump Kit for Johnson, Evinrude 393103, GLM 40820 - Sierra 18-7820 - iboats

If you can use a screw driver then a rebuild is not a problem, just remember where all the pieces came from (some take pictures as a step by step guide so they can't go astray when rebuilding things like pumps). Just take your time and it'll save yourself having to pay out that $100.
Check out the link below, it's pretty close to exactly what you'll be doing.
http://forums.iboats.com/johnson-ev...ble-faq-fuel-pumps-please-comment-240864.html
 
D

dctaz37

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Apr 23, 2006
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Re: 1988 70 hp Johnson bogging down

The part is cheap enough but add $27 to get it to Canada.
 
D

dctaz37

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Apr 23, 2006
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Re: 1988 70 hp Johnson bogging down

Ok I found a kit locally for 18 so I will install it and see how it goes.
 
D

dctaz37

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Apr 23, 2006
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Re: 1988 70 hp Johnson bogging down

Okay not sure what to think now. Went fishing yesterday and boat was fine all day. When I started the boat there was more smoke than usuall and after that no problems. I'm not sure how the fuel pump works but think that it works off the vacuum from the engine. Is it possible there was a restriction that went through? The other difference was that I put too much gas in the tank and closed the vent a bit. Is it possible to have too much venting? Please advise.
 
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