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BF40 40hp 2006 ish hard clunking under load

R

rbis

New member
Honda BF40 2006ish hard "clunking".* I hit something fairly hard about 5 boat cruises ago, (we are having a flood, lots of floaties).* I've also had to straighten out my prop from idling over some branches.* Last boat ride i started getting a flat spot when i power on, i changed the oil and checked the fuel filter, seemed ok,
Boat starts and runs easily.* I can idle around, I can rev out of gear.* When i power on i get lots of irregular clunks like im hitting underwater logs.* Out of gear the prop spins smoothly, in gear in clicks in one direction and the other direction i cant turn it.* The diaphrams in the fuel pump look ok.* I don't think its a fuel problem, although the hose pump doesnt seem to get as 'tight' when i prime it up but that could be just my perception.
Don't know anything about outboards except that i need it to go boating.* Is there a coupling in the gearbox or something?*
 
Re: BF40 2006ish hard clunking under load

Take it to a Honda dealer and have them drop the lower unit and inspect. Sound's like you may have a bad bearing or broken a gear. Possibly the drive shaft bushing has failed. It's not a good idea to run the boat until that is fixed.
 
Re: BF40 2006ish hard clunking under load

Time to take the lower unit apart for inspection.---------------------If you keep running it , then you might have to spring for a new lower or more.
 
Re: BF40 2006ish hard clunking under load

Sounds like you may have bent the shift rod slightly when you hit something and now it is "out of adjustment". STOP using the motor until whatever it is gets fixed! You will only cause yourself more headache and expense otherwise.
 
Re: BF40 2006ish hard clunking under load

Thanks for reply. I havn't used it since the clunking. I've downloaded the service manual. The gearbox selector is not working so well now im playing with it. the oil in the lower unit seems a bit more milky at the bottom plug than at the level plug, not alot came out. there is metal flakes stuck to the magnet on the drain plug so i think im stuffed, bugger. Sounds like i shouldnt fix it myself. Anyone know how many hours i should be charged for it to be fixed?
 
I work on the smaller Hondas, typically the 8 and 20 horse so I don't have specifics for yours. I would say, in general, that a competent shop should be able to repair your gear case in under 5 hours labor charge but the hard parts are very expensive. I have found that on the smaller outboards it can be more cost effective to replace the entire assembly if the vertical shaft is damaged. Yes, it is a few more dollars but the minimal labor for R&R offsets the expense somewhat and you get absolute reliability with a new gear case from Honda. Not sure what's best in your case though.

You are correct in that you probably don't want to tackle this repair yourself. These boxes have exacting tolerances for gear contact depth and selective shims need to be chosen through proper measurement. In addition, the seals and bearings can be very difficult to replace without the proper tools and the unit needs to be bench tested using regulated air and vacuum to ensure a hermetic seal.

I'm not sure what you mean when you state that "not alot came out". Your service manual should have a lube capacity listed and if you mean that substantially less than capacity drained out, then you most likely have a leak. The milky content could also mean water intrusion and that, too, would indicate a leak.

It is not unusual to see a very slight amount of gray "mud" with metallic "flecks" on the magnetic drain screw but "metal flakes" larger than fine ground pepper is not normal. It is a bit of a judgment call. These gears use metal clutch dogs for engagement and each "shift" will cause some metal ablation as with any clutch. That is why I inform my customers to make their gear selections swift and firm so that the dog faces engage quickly instead of "bouncing" off of one another through several revolutions. Firm, deliberate gear engagement minimizes wear in these transmissions. An out of adjustment shift rod will not allow your clutch to quickly and fully engage and that can cause it to self destruct very rapidly.

If you know that you have a good shop to take it to, then I would pay them for a "diagnostic" and then make a decision with them on the best course of action.
Good luck.
 
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Cheers for that. I'm going to make a call on it and say that the flecks are too large. Right now we have our first flood in 17 years and it's looking like it could be our biggest in 36, so all i want to do is get back out there before it goes down (yabbies). Cash is a bit light on so im going to buy a used lower unit and self install. Fix the old one as a spare when times are good ;) Finding one is a bit hard, if anyone knows of a good place it would be much appreciated, the difference between freight across the country or from the states is only about $30 difference, crazy.
IMAG0084.jpg
 
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