Yanmar outdrive and trouble

phildefer · 18 April 2005, 12:06

Hi,

I have found in the forum Threads about outdrive. in one of them I've readen : "I just spoke with another Yanmar owner who's suffered a cracked block this week. He's done some investigation into the problem and found that they all(?) crack in the same place - near an engine mounting. The mounting in question uses three bolts, whereas the mounting on the other side uses four bolts. Also, he tell's me that there are internal oil colling galleries running close to this point. Apparently four bolts could have been used, but Yanmar have mounted some of the external components close by. I don't know if Yamaha do the same. He also tells me that builders such as Mark Pasco move these components and modify the mounting."

This thread was in 2003/2004, Is there still troubles with Yanmar outdrive ?

Thank

Phil

Alan · 18 April 2005, 12:18

There are extensively reported problems with the Yanmar 300hp and Bravo 3 and 3x outdrive. Particularly on bigger boats. Do a search for 'Bravo 3' and you'll find lots of threads.

swginn · 18 April 2005, 12:51

Has anybody got any experience of the new Bravo 3XR drive. Apparently they have solved the associated Yanmar troubles with this one.

http://www.mercurymarine.com/_bravo_xr

codprawn · 18 April 2005, 13:32

Quote:

Originally Posted by Alan

There are extensively reported problems with the Yanmar 300hp and Bravo 3 and 3x outdrive. Particularly on bigger boats. Do a search for 'Bravo 3' and you'll find lots of threads.

I know there are probs with the bigger 300hp - the drives can't handle the torque but what about the 240hp??? Would have thought it would be easier on the drive!!!

jwalker · 18 April 2005, 17:59

There might just be a bit of, 'It ain't what you do, it's the way that you do it.' involved too.

JIY · 18 April 2005, 19:54

My boat has the 250hp yanmar coupled to the Bravo3x. I chose the 250hp, as there seem to have been few problems experienced with drive failures on engines of this size or less.

I did experience a failure of the universal coupling joint at 280 hours - one of the needle bearings in the joint had run dry and failed. On investigation it turned out that a normal Bravo 3 had been fitted to my boat, rather than a Bravo 3x. Laurence Lock from Barnet Marine very quickly remedied this and a brand new Bravo3x was fitted to the boat. The Yanmar engine has now run 580 trouble free hours, the new leg 300 trouble free hours.

The problem with bigger hp engines seems to be related to torque and also overheating. RIBs spend much more time out of the water than other motor boats, so the legs themselves (or at least the gear casings) are often out of the water, and hence lack natural cooling (this is why Redbay fit a shower tube above outdrives). Also, leaping in and out of the water with large amounts of torque is inevitably stressful on gearing and drive shafts.

I'm no engineer, but this is the gist of what the professionals have told me!

phildefer · 24 April 2005, 14:27

Quote:

Originally Posted by codprawn

I know there are probs with the bigger 300hp - the drives can't handle the torque but what about the 240hp??? Would have thought it would be easier on the drive!!!

No bad experiences with yanmar 240 hp and Bravo 2 or 3 ?

Thank

Matt · 24 April 2005, 19:05

Out of interest, what is the peak torque on a 300hp yanmar?

ribraff · 24 April 2005, 20:14

mmm, i think a lot of it has to do with the strength of engine beds and flex in the hulls.

Matt · 24 April 2005, 20:23

Yeh, I understand that's the issue with the block failures, I was interested from the perspective of drives failing

ribraff · 24 April 2005, 21:03

I believe the drives fail as a result of overheating on the UJ's cured by addition of oil shower. Max torque for the 315 Yanmar= 520 Ft. Ib's

jwalker · 24 April 2005, 21:31

Quote:

Originally Posted by ribraff

I believe the drives fail as a result of overheating on the UJ's ...

Nope.

Matt · 24 April 2005, 22:30

top bearing? (Assuming the shower is the fix)