Hi Folks,
2005 Johnson J90GLSOB, carb'd 2 stroke.
I have a qualified marine mechanic assisting me "on the side" with my latest outboard issue, but I wanted to bounce the circumstances off of you good people for some additional ideas...
Original symptom was bogging under load over about 3K rpms, and would not get above 4k rpms. Started to happen about a month ago and was getting progressively worse.
Prior to any repair, we had the boat out on the water for diagnostics...we tested the spark under load and all four cylinders were getting spark (removed plug wires one at a time to test for dropping cylinders). My guy then tested the carbs while underway by using carb cleaner to spray a bit into each intake, and tested by holding his hand briefly in front of each intake to note changes, etc.
Determined that the starboard side two carbs were not getting fuel at higher rpms.
All four carbs were rebuilt this past Friday, including new float bowls. The old ones all showed signs of warping around the rim. Reinstalled and went to put the boat back in the water Saturday afternoon. Started it in the water but on the trailer...started right up but did not want to stay running for more than 30-60 secs and that was at fast idle. Called my guy and he came down after work. Took the boat back out on the water with it running rough in gear but low speed. Now, throttle up and accelerates wonderfully...top rpms back up to 5300 or so, running perfectly smooth top end.
Fools around with the plug wires and carbs some more...determines it's now the port side carbs that are cutting out at lower rpms. So, opposite carbs, opposite problem.
I'm guessing that although the carbs were sprayed with cleaner upon rebuild, there's something stuck/gunked in the port side carbs. They were not mechanically cleaned, just sprayed. Overall the carbs were very clean inside however.
I run the boat a lot during our season up here in New England, and I treat all my fuel with marine Sta-Bil and Seafoam religiously, just as an FYI.
Any thoughts or suggestions are appreciated. My mechanic is good, and I know he will eventually figure it out. He is on vacation through this weekend however, so I am sitting here with my mind racing and dwelling on it!
Thanks!
Dave