Honda BF90A Stalling Problem..help me diagnose

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busski

New member
Have a 2001 Honda BF90A (with carburetors) that's got a stalling problem. At low speeds the engine will stall out unless I squeeze the fuel primer bulb after about 30 seconds to two minutes (depending on engine load).

If I start with the primer bulb firm it will eventually go soft and the engine will stall out after 30 seconds to 2 minutes depending on speed (again unless I pump the primer bulb after which everything is fine for a while)

At anything above 3500 RPM the engine will run fine after a little while (my wife often has to do a couple of pumps on the primer bulb right when we get going onto a plane) , and has no stalling, surging, or other indications of fouled carbs.

I have a 20 gallon tank that is connected via a quick fitting to a sierra fuel water separator.

From the fuel-water separator there is a primer bulb and then a direct quick fit connection to the honda BF90A.

I've replaced all of the fuel delivery lines to the engine except the primer bulb (which was purchased new in October)

Have tried a brand new tank of gas from empty and problem is still occurring

In October a lot of work was done prior to my purchasing the boat. At that time, the impeller was replaced, the intake manifold gasket was replaced, the in line fuel filter was replaced, the carbs were disassembled, sonically cleaned, and synced.

I'm trying to determine if this is:

1) A bad primer bulb
2) Bad fuel pumps
3) Fouled low speed carbs
4) Fouled high speed carbs

Or some other mysterious ailment. Any ideas or suggestions?

Also, any Honda service folks in the anacortes/bellingham area that are well regarded?

-Christian
 
I read your post, several questions occur to me. Is this new gas? Where dif it get purchased? Have you assumed it is good gas or left over from last season. Do you have a water separator? Make sure to drain your separator into a clear container and inspect. The Honda dealer in Bellingham is within walking distance from the ramp. When I have felt with them on the sales end I was happy. Don't know about service, but in a small town likeBellingham your bad you dont last.
 
Well, I had a dealer up in Washington rebuild a Honda carb. I'm not sure what he did, but I had to take it apart to do the correct job.

"Sonic clean" may be just sticking it into a tub and turning on some electronics. That may not clean any of the white stuff that ethanol leaves. I'd start with the carbs. After all, if it runs at high speed it's getting fuel, so apparently it's just not getting the right mixture at idle. Those idle jets are small.

Change the plugs, also.

Boris
 
Christian,
I had the same problem occur on my 2001 90 HP Honda. At 1st, I though it was a clogged Racor filter, but after changing it, I continued to have the same problem. After a few more hours of troubleshooting, I found that one of the two fuel pumps was bad. I removed both bumps and did troubleshooting on the work bench using a simple pressure/vacuum gauge. Pushing on the pump's cam follower I found that one of the two pumps would not hold a vacuum (due to a bad diaphragm, which you can't buy as a replacement item).
Removal of the pumps is easy, as there are only two machine screws that hold each pump in place.
I ordered a new pump assembly from boats.net and all was well for another year until the other pump failed (with the exact same systems). I replaced that pump and all is still well and the engine now has 1035 hours as of yesterday.
 
Since you say the bulb goes soft I would look at the bottom of the pickup hose in the gas tank to see if it is plugged up.

Bill Kelleher
 
Thanks so much for the suggestions.

I'm goin to start with the fuel pickup, then test the primer bulb, then if that doesn't work I'll go to the fuel pumps.

If none of that works, then it's time for the carbs (which I'm personally dreading)
 
Either an air leak somewhere in the fuel intake, or the fuel pump check valve. Low rpm may not provide sufficient fuel to make-up for leak back.
 
I would guess the bulb going soft seems to be a tell tale sign of a bad fuel line, or connection at the racor filter letting air in the system.

If your troubleshooting leads to carb rebuild, you may be able to get the low speed jets clean using sea foam.

I had a similar problem on my starboard Honda 40 where it would run rough at low rpm and stall. I took it to EQ marine and the mechanic was able to get the low speed and idle jet clean using sea foam instead of a full carb rebuild saving us some cash.

Its happened again a year later (bad fuel), and I added two cans of sea foam to one of my tanks and ran it off that tank. It cleared right up.

Something cheap to try before tearing into carbs.
 
First things first I'll try to ensure that there is no leak in the fuel line and that the primer bulb is working as it should. Seems that would be a nice inexpensive solution to the problem.
 
Sounds like another simple case of clogged idle speed jet tube(s) in one or more of the carbs. This is the reason running the engine "dry" is insufficient to clear the carb bowls throughly. You must "drain" residual fuel from each of the four carb bowls anytime you will not use boat for a few weeks!
 
My Honda BF 75 was loosing suction due to a weathered fuel connector. My RPMs were dropping while in the 1000-1200 range and noticed the primer ball was going soft. Also noticed slight fuel leakage around the connector once the ball was primed firm.

The existing connector was only 1yo.
 
Hi all,

Thanks so much for the assistance. It ultimately was the fuel pumps. Am very thankful that those are accessible right on the outside of the engine, with all but one bolt very easy to remove.

Purrs like a kitten now on the jump from Orcas to Friday Harbor!
 
On a previous boat I had a Yamaha engine that had carbs. If the primer bulb was pumped up hard the engine would be flooded. Just took 2-3 squeezes before starting when cold. Never had a hard bulb and the engine ran fine.

I've never actually checked the bulb on my BF90D. Engine starts every time, and I never have to mess with it.
 
I have a similar motor, 2 years newer, with the opposite problem: I lose power at higher rpm, and it runs fine at lower RPM. I have two fuel filters with bulbs downstream from each. I need to regularly pump the first bulb to fill the second fuel filter. My honda tech says it's commonly a bad bulb in this situation and is replacing it, as well as all fuel filters. His list of possibilities were: bad bulb, old filter, clogged high speed jets, but a bad bulb is by far the most common culprit.

If it turns out to be something else I'll post here (still in the shop), but I suppose I'll never know if it was a bad bulb or old filters, as they will all be replaced at once. If it's the high speed jets I'll know, because the new bulb and filters won't work.
 
busski":x74tgdzj said:
Hi all,

Thanks so much for the assistance. It ultimately was the fuel pumps. Am very thankful that those are accessible right on the outside of the engine, with all but one bolt very easy to remove.

Purrs like a kitten now on the jump from Orcas to Friday Harbor!
Click to expand...

Why in this thread are people referring to fuel pumps? One engine --one pump.
What I'm I missing here? BTW I just replaced my fuel pump as there was a small leak around the pump flange. After replacement I pulled the old pump outer flange cover off and as there was no gasket, or O ring to seal the flange cover I became convinced that its the diaphragm outer edge that creates the seal. Therefore, if there is a leak it a tell-tail indication the its the diaphragm that failing.
 
busski":35zf770n said:
Hi all,

Thanks so much for the assistance. It ultimately was the fuel pumps. Am very thankful that those are accessible right on the outside of the engine, with all but one bolt very easy to remove.

Purrs like a kitten now on the jump from Orcas to Friday Harbor!
Click to expand...

Thanks for sharing. I would not have suspected the fuel pump(s).
 
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