Throttle Issue (Not Reaching Full Speed) on Johnson 55HP 1979

[jasondainter]

Hi Folks.

Am new here, and thought I would try this forum out if anyone could kindly help.

I recently rebuilt the lower unit on my Johnson 55 HP from 1979 (to fix a reverse gear issue which now works well). At the same time I took off the two carbs and cleaned them with refurb kit and but pack together, as well as start motor.

Now when I apply the throttle, it speeds up to about 7 knots, then slows down a little with a further push, then peaks there (before I did all the refurbishments it was getting a good 23 knots with no issues).

I filmed it in the attached video at https://www.youtube.com/watch?v=lIu41xvJv8s (sorry for windy sound but I think you get the idea).

One other thing I noticed a lot of black marks (soot?) coming out the exhaust, here is a picture of the first run (it had a new paint job so very noticeable). Not sure if this is connected or an unrelated issue (I cant recall if it was that dirty before) but perhaps related: https://i.imgur.com/36N0Obd.png

Im thinking this must be something I missed or did not align correctly when I reassembled (probably the carbs)?

Any ideas?

 

[oldboat1]

Pretty rig! (Welcome to iBoats.)

What did compression tests show?

 

[jasondainter]

Thanks! I went a bit overboard making it look pretty (probably over compensating for the fact I knew I would break something else haha).

I havn't actually run a compression test yet, I've never done one before so to be honest was going to embark on learning about those a bit later and figuring out if I need more tools etc (maybe that time has come). I did test the lower unit for leaks though and that passed ok (obviously totally different thing though).

My gut feeling is this is very likely something I have misaligned when I put the carbs back on (with some of the the throttle linkages there which came off when getting get those off).

Either that or I've done something wrong when I rebuild the carb, put the floats back etc. I was pretty careful though and think it was correct there.

 

[jasondainter]

Heres a photo I took if it helps at all after the problem occured.

A few questions I wondered if you could be so kind as to shed some light on (and help me learn a bit in the process).

1) does the "start" position look correct to you here?

2) The metal wire that dips down into the little "magnet thing" (im sure this has a better name), it looks at a weird angle perhaps, is it supposed to bend down like that and could this have any bearing on my issue?

3) The adjustment screws (bottom of pic). I think I recall this was for forward and reverse minor adjustments (not for throttle) is that correct? They are left how they were before I fixed reverse gear (new gear/clutch dog) which now works fine so I havnt touched them.

4) On that gasket seen just behind the silencer box, it looks like its flopping about a bit under there. Seems unusual considering gaskets are supposed to seal things. Im pretty sure I wouldnt have installed it loose but I think I'll take off the silencer box and double check thats sitting where its supposed to be.

5) In the picture to the left of the "start" metal plate there is a creme coloured screw holder with a screw that can be adjusted. When I put the unit back, I wasnt 100% sure it went back on with the same number of turns (stupidly I didnt document that before I took it apart). I think anyhow it can be adjusted, do you know what that does and if it might relate to my issue?

Im going to do some reading up in my service manual (I have one luckily) on link/sync process. Id have to take the boat back out the water to do that so was hoping a bit it was a more simple fix at least until the autumn (I lost a lot of summer time here in Sweden by refurbishing the lower unit already!).

Thanks!

 

[jimmbo]

A link and sync can be done a garden hose, or tub of water. Doesn't even have to be running

 

[jasondainter]

OK thanks thats certainly my next stop.

Any ideas on the questions above?

 

[JerEazy]

It seems like the timing isn’t advancing properly with the throttle and fuel. Mine did the same thing when some backyard mechanic “fixed” my starting issue. If you moved/adjusted something when you took the carbs off you could have knocked it out.

Do you have a factory manual? I will grab mine and reference the pages for you if needed. But you need a link and sync and idle/throttle adjustment.

With the engine off - Put it the engine at WOT and make sure the carbs are opening all the way, the roller cam is being pushed open properly by the arm. And do the joereeves timing method as well.