Bf90a running in 3 cylinders

[Dstacey]

I’m totally new to this guys so please take it easy on my lingo. I’m not a mechanic and don’t know much about this boat at all . My problem is I have a 2001 bf90a that is running on 3 cylinders. I did the drop
Test (removed plug wire one at a time while running #2 made no difference when I unplugged spark plug wire)
Other 3 cylinder drastically changed idle or caused engine to stall. Checked for spark and appears to be firing same as other cylinders, ( removed each plug and turned over motor to get a visual of the arc between plug and block) also
When I pull each plug wire from plug while
Running I hear a loud clicking or arcing from the plug wire itself on all 4 cylinders. The arcing seems to sound the same and have the same rhythm. I removed the linkage for the choke and closed off the choke on the bad cylinder but didn’t get any response. ( I read that was a test to see if it was fuel
Or spark)
Compression was 182,177,180,180i guess my question is , should I assume it’s fuel related and have carbs rebuild or is there something else I can check to narrow down my problem.
I just got this boat. Only got to take it out one time. Wouldn’t go above 4k rpm wide open throttle at 15 mph (24 ft pontoon 5 people on board). Ran perfect until we pulled up to dock to load up. Died and wouldn’t start up. Any help
Would be appreciated

 

[jgmo]

Hi,
Nothing like getting a new (to you) boat and having it crap out as you load up the gang for some fun.
Feeling your pain!


I haven't worked on the 90hp so just some thoughts about this.

Your testing and results seem valid so far to me.

I'm guessing, right along with you, that #2 carb isn't feeding fuel correctly for some reason But, it's just a guess.

Could the float be stuck closed?
You could open the drain screw and see if there's gas in the bowl. Then squeeze the bulb and see if gas flows out the drain. You could also compare what that one does with one or more of the others.

You could spritz carb cleaner around the intake and mount gaskets to see if it will pick up that cylinder temporarily.
And, check all those 20+ year old vacuum hose segments for splits or cracks. You can spritz those too.

Speaking of 20+ year old hoses, the fuel hoses are known to deteriorate internally and can sometimes develop a "flap" inside that can act like a valve closing. They can also form a bulge or "bubble" internally that can reduce or block flow. If you clean the carbs you might consider replacing all the hoses as a precaution.

This engine has two fuel pumps so you might want to compare the flow from each to see if it's fairly equal.



Because it seems carbs 1,2, and 3 are all the same, you probably could prove it beyond doubt by swapping #2 with one of the others and see if the problem follows but I wouldn't. Too much hassle. Once you've done that much teardown you might as well proceed with the cleaning.

There are many items for this outboard that are no longer available from Honda. I've never let that stop me though. But choose your "parts path" carefully as you work through the fix for this problem and don't misplace anything.

I hope you get this sorted out without too much additional suffering. Boats are supposed to be FUN after all!

Good luck.