1989 48hp Johnson on 1 cylinder

Les Robb

Chief Petty Officer
Joined
Jun 14, 2009
Messages
435
This is a little bit of an SOS. Bought the boat and engine about 6 months ago and other that rough idle it's always run like a top in the lake near home. Well here we are 500 miles away and we minimum waked for about 500 yds and lost the bottom cylinder before we hit the resume safe speed. Soaked carb last night in gunk cleaner and spent the morning on the driving to get rebuild kit. Now we have fuel getting to bottom cylinder and although the needle valve can be adjusted it will not smooth out and allow for advancing the throttle. Can throw a blue spark 1/2", on both cylinders and the plugs are new with proper gap. Only 2 days left of vacation and any help would be appreciated.
 

Les Robb

Chief Petty Officer
Joined
Jun 14, 2009
Messages
435
Sure did, thought maybe I had a broken ring. Anyway 150 on the bottom and 145 on top.
 

Les Robb

Chief Petty Officer
Joined
Jun 14, 2009
Messages
435
It seemed to be a fuel problem at first, but rebuild and cleaning solved that.I did have both lines off and they are good.
Thanks
 

jakedaawg

Rear Admiral
Joined
Jun 26, 2012
Messages
4,275
Have you taken a fuel sample? I wonder if your flooding the bottom cylinder
 

Les Robb

Chief Petty Officer
Joined
Jun 14, 2009
Messages
435
Key possible but top cylinder running fine, and I can adjust the flow of fuel to the bottom carb to be noticeable at minimum idle. Also played with adjusting needle valve in and out of the water yesterday. You can choke it out and stall it down. No time or tools here to pull the flywheel and my Factory Service Manual is right where I left it when we were packing and I decided not to take it. Oh well, we will fish on the jetty this afternoon. Thanks again for all the replies.
 

Les Robb

Chief Petty Officer
Joined
Jun 14, 2009
Messages
435
Home and finally had a chance to do a few more tests. Link & sync okay and firing evenly on both cylinders per timing light. Also disconnected priming hose and confirmed gas was not leaking into carb. Starting to think I have a reed problem on the bottom cylinder. I can't think of anything else that could be causing this and it would explain how it went from running fine to zip in a flash. Back to work tomorrow so won't tackle again till the weekend. Just wanted to keep you advised as it may help someone down the road and if anyone has come up with any more ideas, please let me know.
 

Les Robb

Chief Petty Officer
Joined
Jun 14, 2009
Messages
435
Update: 2 of the 4 bottom reeds are slightly ajar, one about 1/32" and the other barely open. At the very least that would account for the poor idling.
Since new reed plates are not available anymore, any suggestion on where to get besides used on e-bay etc.
 

halibutts

Cadet
Joined
May 29, 2015
Messages
27
I think that I read in a manual that if the reeds are bad you get some backfire?
 

Les Robb

Chief Petty Officer
Joined
Jun 14, 2009
Messages
435
Well can't say backfire, but after taking the reed assy's out the 2 of the 4 lower ones were definitely not closed. Went ahead and ordered a used intake assembly with reed valves on ebay. Will update after parts installed.
 
Top