1989 jonhnson 48 spl timing issue

[Nick2020]

I bought a boat that has a Johnson 48 spl but when I try to start it it backfires and sounds like it is firing at the wrong time. I also saw that the flywheel nut was welded to the flywheel and thought something could be wrong with the flywheel or under it. What could I be looking for?

 

[oldboat1]

Woof. Flywheel nut literally welded, or rusted in place? Possible (maybe likely) the flywheel key is sheared (i.e., flywheel has moved on shaft, changing the timing).

It's possible the mixture is set too lean, giving you a lean sneeze, but don't know offhand if your SPL has a fixed l.s. jet (vs. adjustable needle). Consider using an air wrench to remove the flywheel nut so you can see what’s happening.

 

[racerone]

First I have heard of this welding trick.------Sounds like you have to use a Dremel to get the nut loose.------Then remove the flywheel.-------Then inspect key and tapers.-------Tapers must be matched ( lapped ) together.-----Assembled clean and dry with new FACTORY key.----Nut torqued to 100 FT-LBS.-----Hopefully you can salvage the crankshaft.----Lots of those cranks available used.

 

[Nick2020]

I was able to cut off the welds and remove the flywheel and sure enough, the key was completely sheared. Thank you very much for the diagnosis.

 

[jakedaawg]

Pay very close attention to the repair racerone mentioned. None of those steps are skipable...