70hp problems???

[aspeters]

hello!! i've been reading posts of this site for a while now and just have joined. maybe some one can lead me the right way.i bought a 16' bass boat with a 1977 70hp johnson motor,nice boat and the motor seems to be strong but i can not get any top end the fastest i've had it to was 10mph. i've had it in the shop a few times and always told its fixed but when i get on the water its not!!! i've replaced sparkplugs,fuel line,fitting on fuel tank and checked to see if all spark plugs were firing and they were.I've got a orange color wire that has been cut at the top right hand side of the motor that goes stright into the motor but can't find were it goes to, i don't know if it has anything to do with my problem but it got to go some where. so let me thank ya'll for taking the time to read this and please if any body has any info please let me know,i'm new to boating and just learning about it and have a long way to go! thank you!! andy

 

[tashasdaddy]

Re: 70hp problems???

have the carbs be dismantled soak, cleaned, and reassembled with a new carb kit? what are the compression readings? has a link n sinc been done? if it runs at all the wire is not the problem.

 

[aspeters]

Re: 70hp problems???

thanks for the reply but i put it in the shop to have the carbs checked out and cleaned but the problem still stands the other day i took it out and when we was going back to the boat dock the motor started running betters and picked up speed but i think it should still be a little faster. do you think pumping out the fuel and replacing it with 93 octane well help? the feul in it is pretty old it was in it when i bought it 6 months ago and i don't know how long it has been in there. thanks for taking the time to help me!!!

 

[twinriver]

Re: 70hp problems???

I would drain the fuel, but it does not sound like that is the whole problem. Check the fuel line right before it splits to the carbs. Mine developed a crack in it and my motor would start and idle fine, but would not go on plane. It was not leaking fuel and not visible without removing and flexing, but was big enough to suck air. A quick trip to my waterfront shadetree boat mechanic and he found the problem after watching the motor run for about 10 seconds(some things come easy to a boat mechanic with 40 years of experience). A 4 inch piece of fuel line can sure derail a fishing trip. I was lucky I was around the marina and could get it fixed.

 

[aspeters]

Re: 70hp problems???

my old fuel line was dry rotted at the end where it connets to motor but it has been replaced with a new one and i still have the problem. i was wondering about the fuel pump, how would you know if it is going bad? when i run the motor and pull off fuel line you can hear the pressure on the line. so i don't know.

 

[david_r]

Re: 70hp problems???

if you think its your fuel pump try pumping the primer while under way. if this doesnt help its probably not your fuel pump.

 

[aspeters]

Re: 70hp problems???

i took it out and while running i could pump primer bulb and fuel line was not empty but wasn't full either and motor picked up a bit but not like it should. could this be a fuel pump?

 

[evinrude lover]

Re: 70hp problems???

i took it out and while running i could pump primer bulb and fuel line was not empty but wasn't full either and motor picked up a bit but not like it should. could this be a fuel pump?

I have a 70hp that the carbs were cleaned fuel pump is new and is bogging down on take off. I spent all day trying this an that on the water and i still have the issue. going right now to tighten up those fuel lines again.