78 johnson 70hp dies when it goes in gear

[jakesdog]

I have a 1978 70hp Johnson that I had carbs rebuilt last year along with a new fuel pump kit. I went to put it in the water and it wouldn't idle unless I had it choked. When I'd put it in gear or would try to rev it up it would die. So I put in new plugs and put it back in the water this time it started up fine idled fine, no choke, reved up fine, but as soon as I put it in gear it would die. I even got my brother to hold the idle up manually as I put it into gear. No luck. So we pulled it out of the water started it up put it into gear and it worked fine so we left it in gear about half throttle and as soon as the motor went under it would bog down and die. We did this several times with the same results. So if anyone can help me I'd appreciate it.

 

[tashasdaddy]

Re: 78 johnson 70hp dies when it goes in gear

check compression, and spark, post results, you also, just burnt up your impeller. i pull an impeller this morning that had been run dry, it had started to melt, and had clogged the water outlet of the water pump, into the water tube.

 

[dooma_Flatchy]

Re: 78 johnson 70hp dies when it goes in gear

I have a 1978 70hp Johnson that I had carbs rebuilt last year along with a new fuel pump kit. I went to put it in the water and it wouldn't idle unless I had it choked. When I'd put it in gear or would try to rev it up it would die. So I put in new plugs and put it back in the water this time it started up fine idled fine, no choke, reved up fine, but as soon as I put it in gear it would die. I even got my brother to hold the idle up manually as I put it into gear. No luck. So we pulled it out of the water started it up put it into gear and it worked fine so we left it in gear about half throttle and as soon as the motor went under it would bog down and die. We did this several times with the same results. So if anyone can help me I'd appreciate it.

Let me ask?

You put in half throttle out of the water You defiantly want to change the impeller.

 

[mikesea]

Re: 78 johnson 70hp dies when it goes in gear

your carbs got dirty again,it will run better out of the water because there is no back pressure ,also agree on the impeller advice if you didnt put water to the impeller

 

[BoatBuoy]

Re: 78 johnson 70hp dies when it goes in gear

You didn't say what plugs you are using, but they should be L77JC4 gapped at .030.

EDIT: And the water pump stuff already said.

 

[jakesdog]

Re: 78 johnson 70hp dies when it goes in gear

Well I'm getting spark and ran a compression test and it got 75psi on all 3 cylinders, I don't know if thats good or bad. I'm not sure what a good compression would be on a outboard. I'm used to working on cars. Also I put it in a barrel and it still pumps water out as good as before, but I'll check it out anyway. I took off the drains on the carbs and sprayed them out and didn't see any crud coming out. It got dark so I'll see what happens tomorrow when I put everyhting back on. Also I got to thinking about when I got the boat back from getting carbs rebuilt it ran good when trolling but had no power at full throttle, it just did not seem to want to go. So it may be something with carbs.

 

[jakesdog]

Re: 78 johnson 70hp dies when it goes in gear

Oh and the plugs are the right ones too.

 

[the machinist]

Re: 78 johnson 70hp dies when it goes in gear

I had that same problem once on a 50hp, & the situation was that there was LOLTS of nylon fishing line wound on the prop shaft under the prop, creating excessive drag when you put it in gear in the water.

 

[jtexas]

Re: 78 johnson 70hp dies when it goes in gear

remove carbs, disassemble, soak overnight in carb cleaner, blow out passages with compressed air (or aerosol carb cleaner), reassemble with new carb kits, reinstall, link & sync, replace water pump.