70hp issues

[nmhellraiser]

I've got a 1978 johnson 70hp that is giving me issues. First off, the electronics have been converted to the newer style power pack instead of the old power pack with all the screws. Anyways, the boat has been running good until this morning. I was trying to get the tach hooked up and it was just a bad ground so I re-grounded it and now my problems begin. It will start and idle for about 1 minute then dies like it's not getting fuel. The carbs were rebuilt less than a month ago. The bulb is staying hard. Could it be the fuel pump? I can start it and put it in gear and it will rev up then just loses rpm's and dies. Any suggestions?

 

[Bifflefan]

Re: 70hp issues

I was trying to get the tach hooked up and it was just a bad ground so I re-grounded it and now my problems begin.

Unhook the tach and see if it runs.

 

[nmhellraiser]

Re: 70hp issues

Unhooking the tach made no difference. I finally got it to idle and run so I put it in the water and it wouldn't break 2400 rpms and I had to bump the choke to get it to raise the rpms. I figure it's a carb issue now. I took the carbs off and cleaned every orifice and jet. They weren't clogged or dirty but now it idles better. I'm about to go put it back in the water and see how it does. The only thing I changed is the oil/fuel mixture. I mixed it 40:1 and dumped a can of seafoam in the tank b/c it has been setting for a month or two. We'll see how it runs here shortly.

 

[nmhellraiser]

Re: 70hp issues

Alright, took it back out this afternoon for the 3rd time. I guess cleaning the carbs helped somewhat as I'm able to get on plane now and it will somewhat idle. It's idled at 1100 RPM in the water. Can't go any lower or it dies. I'm thinking I've still got carb issues though. At 2k rpms if I try to throttle up, it dies. I have to bump the choke once to get over 2k rpms then it takes off and runs fine. Thing is, the carbs weren't really dirty in the first place. All the jets were clean. All my fuel lines are new on the carbs and inside the motor. I guess maybe a new fuel pump and new line from tank to motor? I checked compression and I was 120,118,&120. Any other opinions?

 

[nmhellraiser]

Re: 70hp issues

I'm bringing this back to the top. This issue is about to kick my ***. I'm usually pretty good troubleshooting things but can't figure this issue out. I've taken the carbs apart for the 4th time and used compressed air and carb cleaner to blow everything out. There's not any resistance, corrosion, ect.. wrong with the carbs. It starts and idles, a little high (1000rpms), but when on the water and I adavance the throttle to quickly, it dies. If I ease the throttle and bump the choke once at 2000rpm's, it takes off fine and doesn't miss a lick. All fuel lines are new. The bulb is staying hard during the whole process. The vent is open. I'm replacing the fuel pump today. Any other suggestions?

 

[eclark53520]

Re: 70hp issues

This probably isn't much help, but i have a 77 70hp and i've experienced almost the same issue. Although, I've never had a problem at idle.

My fuel pump is 2 years old but every once in a while it will only give me 2500 or so RPM's at full throttle. Sometimes i can let it high idle or a while and it will run fine after that.

Its completley random though. Some days it will only ever get to 2500 no matter how long i run it and other days i'll never have a problem with it running full throttle. I can start it cold at the dock, and it will run wide open all day long. I'm at a loss as to what the actual problem is.

Almost makes me think its something to do with the ignition since its so on-off.

 

[nmhellraiser]

Re: 70hp issues

Mine will run all day long WOT but I have to bump the key sometimes to get it over the 2000-2200rpm mark. Once above those RPM's, it runs smooth. Everything seems to be pointing at carbs but I can guarantee they are clean and nothing in them.

 

[Stokes81]

was this problem ever resolved ?

 

[fireman57]

The mods really don't like you bringing up threads from almost 6 years back.