New Member Yellowtail Needs Help

[Islandtrader]

I thought I would do a cut and paste for this member(yellowtail) since his question might get buried in the other thread.


Hi everyone. I am a new member and am not sure if I am posting correctly as this is my first post but I could use some input from the group. I have a 1976 23 ft inboard Scepter and am running a 240hp Yanmar 4 cyl. diesel down here in Baja. The other day coming back in I burned up my front bearing in the v-drive for no apparent reason as it was full of oil and the cooler was working. I was lucky enough to find guy with a rebuilt drive here which he thought was a 1.5-1 like the one I had but after installing it and sea trialing the boat I found I could not get the boat up on plane at WOT. Obviously it is a different ratio. Prior life I was running a 4 blade 16x18 prop with slight cup and ran 23 -24 knots at 3000 rpm burning 7.5- 8 gals per hour. We installed a 3 blade 17x 24 and now I am running 20- 21 kts at 3000 rpm and am burning 6 gals per hour with a heck of alot of rumble but at least I am running now. Any suggestions as to where I go from here? I was very happy with prior performance of the 16x18 but have no idea how to get back to where I was and wonder if I might have been stressing the drive previously and may be better off running a little slower. I would be ok with the slower speed if I could get rid of the rumble and wonder if cupping the prop would help? Any comments would be appreciated. I will post pictures of the boat as soon as I figure it out. Thanks

[NoBones]

I tried Terry..
Gucci is gonna have to move the post out of Performance.
My authority will only work within my section..

[bitsamonkey]

From what other inboard users have reported, the tunnel in the inboard hull limits the diameter of the prop you can run without that rumble. I believe you can decrease diameter by adding another blade. If you could find a 4 blade 16x24 you'd probably be in better shape. The whole idea of reduction gears is to be able to run a bigger diameter prop at slower rpm as that is more efficient, since you're limited in diameter by the tunnel you might have to look for a differently geared drive. If you still have your original drive you can easily rebuild or have it rebuilt. It is crucial for the nut inside the output flange to be torqued to specs as it pulls two sets of conical bearings tight and aligns the shaft. If your drive was leaking out of the back seal make sure the output flange surfaces are square and everything seats properly. I believe aligment problems in the propshaft will cause these problems over time. The drive should easily handle the loads you're talking about.

[bitsamonkey]

Just re-read your post. If the bad bearing is in the transmission and not the reduction gear, then all you'd have to do is swap your reduction gear to the new tranny. That's easy.

[gofastsandman]

I would tear down the old v drive and call BW. Then call Ken at propgods.com. Can you, or a local, service the drive? Was the oil cloudy/milky? Maybe BW or Ken knows someone down there.

Cheers,
GFS

[yellowtail]

Thanks for the input. I still have the 16x 18 four blade prop and wonder if I could get it cut and rewelded to make it into a 16x24 or 16x 25 and if that would give me back the lost performance. My transmission guy could possibly be persuaded to open and rebuild the original v drive or swap gears to get me back to a 1.5-1 as well but he says that he doesn't rebuild them. My options down here in Baja are very limited as there are no prop shops and very few people that work on transmissions and drives. When the v drive went out it got so hot that the paint burst into flames so I am not too hopeful that a lot can be salvaged from that drive.