BF90 (Carb) stalls under fast load

[totallydave]

Originally Posted by tworotorturbo

I had the same issue on my BF90. It ran excellent but would stall when given instant WOT. The tiny jets got clogged. Its a fairly common minor issue.

Hi, what was necessary to fix - is it a carb strip down and clean? or simply a case of of running some fuel additive. I need to get an idea of what to ask my service agent to do ~ or what I may be able to do myself.

Thanks.

[totallydave]

Originally Posted by tworotorturbo

I had the same issue on my BF90. It ran excellent but would stall when given instant WOT. The tiny jets got clogged. Its a fairly common minor issue.

Originally Posted by 9D280

Nos,

If it is just an idle mix problem all he needs is a screwdriver and a stretch of water to run the boat!

I have just found this very useful article

The Outboard Expert: Curing the Honda BF90 Bog - Articles - boats.com

It describes exactly the issue I have and cites it as a known 'design flaw'. It does refer to changing mixture (with photos) as one option, but cites a smaller prop pitch (to ease the load) as another, perhaps better option.

What do you guys think of this? If you think it is a good idea, I will look elsewhere on the forum for anyone who could loan an appropriate prop for a trial.

[9D280]

Originally Posted by totallydave

In a previous trip to a service agent, I had the carbs 'balanced' (but not cleaned). I watched this and saw that he adjusted 3 screws (one cyl was 'base set' and did not have a screw). Not sure if this is the same thing or would have involved the mixture?.

Like I said I don't know these carbs, but I would guess that "balancing" would alter the mixture. Certaily any outboard carbs I've ever taken to bits the main jet was a case of pick & fit the jet size & forget. The "idle mix" is the one you fiddle with.

Originally Posted by totallydave

I looked at the documentation on boatinfo (not bad but poor copies) but could not see any specific reference to a mixture screw..

It may also be a naming convention thing. What I call the idle mix Honda might call something else. In my work there are some components can have up to 5 different names depending who you speak to!

Originally Posted by totallydave

I get the whole point of take a note of current settings and return them if it doesn't work, and I am comfortable with this concept but unless it is 'bleeding obvious' where the mixture screw(s) are, I am probably erring on Nos' advice of take to someone who does.

If you are unhappy doing it yourself there's no shame in going to a dealer. Better that than a dead engine!

[tworotorturbo]

A carb strip down and clean. Ran excellent afterward.

When I had the problems, I read that same article too. The idle mixture did not have to be touched after the tiny jets were cleaned out. Good luck and keep us updated.

[Peter_C]

Idle jets can sometimes be cleared by holding a higher RPM, like 4,000 or more, and putting a beer can or whatever seals off the end of the carb. You only want to create the vacuum for a few seconds then let the engine recover. The high vacuum with often clear any debris blocking the jets. I have done it multiple times and it often works.

Sometimes you can blow into the jets without removing the carbs too, but you would need to inspect them to find out which one is the idle jet.

[mhb100]

Originally Posted by Peter_C

Idle jets can sometimes be cleared by holding a higher RPM, like 4,000 or more, and putting a beer can or whatever seals off the end of the carb. You only want to create the vacuum for a few seconds then let the engine recover. The high vacuum with often clear any debris blocking the jets. I have done it multiple times and it often works.

Sometimes you can blow into the jets without removing the carbs too, but you would need to inspect them to find out which one is the idle jet.

I have a Honda 90 carb and pro open 550. I have a manual on disc somewhere and should have a couple of props, although boat is in Devon right now, but I'm also working out of Basingstoke. I'm no expert but happy to drop by after work one night. I've also got a 4 gauge carb balancer somewhere. I've never had the problem. Pm me if you want me to drop by. Mark

[mick]

Not had any issues with mine 2 x 90 as yet apart from tricky to start when warm my props are D3x13.25x17R as recommend by Honda, and they have covered some distance

[CDK1]

My son has had idling issues with his Johnson 50 for several years. Instead of taking the carburetors apart, this summer he came armed with an expensive spray can "Evinrude carb cleaner". I am a skeptic, but after spraying the stuff in the air intake and drinking a can of beer, the engine ran as new!

There's no magic involved, the stuff is just a mix of MEK and toluene.

[9D280]

Running an engine on beer??? at £2.30 a pint you'd be cheaper burning petrol!!!

Joking aside - the one down side to spraying carb cleaner in is that some of the cleaners will attack rubber type compounds like O- rings. Spraying into an engine you may find shaft oil seals & the like on the intake side get prematurely aged / destroyed if you get enough cleaner in the wrong place...

I'm not trying to scare - but be aware. I did a test on an old Viton O- ring after I cleaned my carb a while ago. I forget whose clenner it was but after a 2 hr swim the ring had become really brittle & disintegrated when touched.


Carb cleaner - yes. Straight into an engine - be aware!

[totallydave]

Originally Posted by mhb100

I have a Honda 90 carb and pro open 550. I have a manual on disc somewhere and should have a couple of props, although boat is in Devon right now, but I'm also working out of Basingstoke. I'm no expert but happy to drop by after work one night. I've also got a 4 gauge carb balancer somewhere. I've never had the problem. Pm me if you want me to drop by. Mark

Thanks Mark, I now have the manual (but still not going to attempt any Carb work myself). The option to try another prop is appealing - I will PM you to see if there is any opportunity to work this out.

Dave