Johnson 70 help

[DAN M VAGOS]

Hi all just upgraded to a bigger boat and it came with a 1999 Johnson 70hp. The guy told me he used it in the fall with no problem but it's still 15 outside so I could not test run the engine. Also it came off a ferry and was in they parking lot so there was no water to test it. So I did comp test on it and it was 145+- on all three and it had spark. So for my problem I hot it home and tryed to start it and it just cranked and cranked but he told me his tec fogged it so I new it was going to be hard. After sum time it did fire up but ran like it had a miss but smooth at higher rpm. When I first saw the boat and did my inspection I saw one plug #2 was new and #1/3 where definitely used, well after getting fired up in my yard that one plug still looks new. I moved the plug to #3 and ran it and it still looks new. So what's the chances it's just a bad new plug.

 

[Faztbullet]

Re: Johnson 70 help

it was 145+- on all three and it had spark.

Did this cylinder have spark? Do a cylinder drop test while running and see it that cylinder is working. It is possible that the plug is fouled and not firing under compression or it could be defective. That motor isthe lost foam cast so it does not have exhaust plate that leaks like the smaller cc 3 cylinders.

 

[DAN M VAGOS]

Re: Johnson 70 help

Yes all 3 had spark. And what do you mean cyl not working? And the lost foam motor ? Is this a better engine

 

[phillnjack2]

Re: Johnson 70 help

of course its a better engine its a lot newer design for a start and more modern in more than a few ways.
its 920cc , the older model was 849cc.
The cylinder head is also different and just a single piece although it does look like it seperates it realy does not.
you will have quick start function and also slow mode function.
more low end torque and a better smoother idle than the older model.
lost foam is how the engine block was cast at the factory, the older engines had a different exhaust plate that was a know problem that often leaked gas or water into the combustion area !!!
by cylinder dropping test I presume he means have it running then pull a plug lead and see if the engine rpms drop, then do the next etc.
if a cylinder is dropping it will show up when you do this.
I would first check and clean the carbs if you get a good spark on all 3 cylinders.
.
have you cleaned the carbs out ? if its been sitting its probably got gummed up carbs. especially if any fuel left in the carbs when last run.
.
if the dealer realy did winterise the engine make sure you check the gearbox oil too, as some dealers have been known to completely drain the gearbox during winter, this is not realy good practise as it can cause problems, anyway check it to be on the safe side.

just my thoughts on it.

 

[racerone]

Re: Johnson 70 help

Did you do the compression test or the previous owner ?----

 

[DAN M VAGOS]

Re: Johnson 70 help

I did the comp test and I did just put new plugs in and it seems to start right up and run ok. A lot of smoke but it seems ok. And I did just do a cylinder drop test and yes when I pull the plug wire off it did make a difference so maybe it's all set.

 

[DAN M VAGOS]

Re: Johnson 70 help

Hi guys I just uploaded a vid of it running. Please let me know if you think it is still skipping. The video is on YouTube and the name is Johnson 007dan and my user name is danielv508

 

[DAN M VAGOS]

Re: Johnson 70 help

Any idea

 

[DAN M VAGOS]

Re: Johnson 70 help

Anybody

 

[jb93]

Re: Johnson 70 help

You can upload video here into your thread...maybe help you get a reply.
Click on icon that looks like a film strip then you can insert url.

 

[DAN M VAGOS]

Re: Johnson 70 help