Logo
FULL SITE MENU

Does this sound like a lower end knock - with video?

M

metal-chicken

Regular Contributor
I've noticed what I suspect is a bit of a knock from our new-to-us BF225 (2007, unkown hours) - but I've not run the engine much so I may be wrong.
We had it fully serviced (inc lower oil change) by a recommended guy who is a Tohatsu dealer, and they said it was all good. I did ask them to check the mid-shaft bearing and when I asked about it they came back and said it looked fine ..... but I'm not convinced it was actually checked.
Anyway here's a video from earlier today when it was idling - not sure if it sounds OK or not :confused:

I also noticed that when I tilted the engine up completely the drops of water coming off the engine where leaving an oily sheen on the water - but this may be just because it's recently been greased, etc.
 
Last edited:
It is hard to tell from a video. It sounds more distinct on the port side.

Take a long pole....broom handle, boat hook, or something similar that you can stick down into the water against the lower unit, then put it up to your ear to listen for the sound. Touch the pole at different places on the motor to see where the sound is loudest.


Mike
 
Also, let us know what happens with the knock when you put it in gear at idle. (And make sure you have someone on the helm while you're listening!)
 
When you say lower unit, where in the lower unit? In the leg or the bulb behind the prop? In gear or out of gear, or both?
 
I'll have to check again but when I listened earlier it was idling out of gear and I just listened down the leg and it was loudest at the bottom at the leading edge of the unit. I'll try to do another check tomorrow in more detail.
 
So I got back to the boat today and changed the O2 sensor (success!) and took the boat for a quick run. After running at about 4200rpm for about 5 mins the engine slowed then stalled.
Battery 1 wouldn't turn it over so I swapped to battery two and that managed to turn it over and the engine started but when I put it in gear there was plenty of banging/crunching and no drive after about 3 seconds. Engine subsequently started easily but no drive in forward or reverse and no knocking sound. I managed to get a tow back in to the mooring. Externally the lower unit looks fine but I can smell gear oil.

I suspect the original knocking was coming from the pinion gear which has finally disintegrated.

Is there anything I can test while the boat is still on the water?

The joys of buying a used engine - new gearbox time it seems :(
 
Don't think so. You need to haul the boat and drop the lower unit. Don't forget the bolt under the trim tab. If it's toast, you can find rebuilt ones on the Internet at a reasonable price.
 
Ouch! I know that rebuilding the lower gearcase is NOT the way to go. So many failures. These guys here can direct you to buy a decent remanufactured unit or you can buy a new complete unit from boats.net for around $3000. You might be able to find a complete parts motor, I was lucky and picked up a spare outboard with blown block for $200
 
I went back out to the boat today to do some other stuff and ran the engine so I could listen again with the use of the boat hook. Nearly all the sound has gone although I can still hear something rotating, presumably the drive shaft, and there is a bit of vibration/oscillation that seems linked to the shaft rotation.
Putting it in either gear made no difference to the noise. The cooling water tell-tale is still as strong as before and the engine sounds sweet so I'm assuming the drive shaft is fine.
I then switched the engine and batteries off and tried turning the prop by hand. I neutral is span freely but I could also turn it when in gear although I could feel and hear grinding as it turned - I'm fairly sure that if the unit was undamaged I wouldn't be able to turn the prop when in gear.
My feeling is that the pinion gear has destroyed itself and that what's left is mush.
I shall report back once the lower unit is off.
 
I thought I'd add an update to this.
Rather than save a bit of money and buy a new gearbox from the US (I'm in the UK) I went with our local Honda dealer who brought a new box in from Belgium.
Pulled the boat yesterday and they removed the old box.... Which turned out to be an xl shaft and not a long shaft that the serial number said it was.
So another box is being shipped from Belgium now and hopefully we'll be back up and running in a few days.
The dealer stripped the old box to see if the drive shaft could be swapped but it turned out to have snapped due to a faulty bearing which had cooked the oil in a short space of time.
Inside on the old box is mush.
Glad I went through the dealer!
He also plugged it in and did a print out of the engine history. 690 hours.
 
Final update - new lower unit installed a couple of days ago and all is good (well, apart from potentially having the wrong prop but that's another thread!).
 
Good to hear.

Just a caution - it's not good to run a BF 225 on muffs. Not enough water gets in there to adequately cool the engine, plus it's tough on the impeller.
 
I hear you on that, but it was the Honda dealer who did that test! Interestingly they had very good muffs which were fed from a small reservoir tank which was full before the engine was started (and it was constantly refilled by the hose) so it could take more water than if it was being fed by just the hose alone.
 
Back
Top