Why are inboard engine shafts angled down ?

[Pete H]

The reason I might want to keep the engine level is that I am building a small steamboat and it may make installation easier. I am planning to us a thrust bearing because the bearings in the engine are not thrust bearings.

[Garret]

The reason I might want to keep the engine level is that I am building a small steamboat and it may make installation easier. I am planning to us a thrust bearing because the bearings in the engine are not thrust bearings.

Fair 'nuf! I'm sure experts here can tell us about the best way to do this, but one thing I'd consider is a constant velocity joint (like one in an axle of a FWD car) instead of a U joint. They are much smoother.

[carioca1232001]

Fair 'nuf! I'm sure experts here can tell us about the best way to do this, but one thing I'd consider is a constant velocity joint (like one in an axle of a FWD car) instead of a U joint. They are much smoother.

A Constant Velocity (CV) joint-cum-thrust bearing in the same piece :

https://www.vetus.com/en/stern-gear-...-5-flange.html

[David W Pratt]

Ian's suggestion of Dave Gerr seems a good one. He has some successful tunnel drive designs. One advantage evidently is running at speed over known bars and enjoying the surprise in the audience that you didn't rip the stern gear out.

[Garret]

A Constant Velocity (CV) joint-cum-thrust bearing in the same piece :

https://www.vetus.com/en/stern-gear-...-5-flange.html

Perfect - though I bet it's not cheap... Nope - about $1700 US.

[carioca1232001]

Vetus´ engine-to-drive-shaft couplers are renowned for their prowess in subduing noise and vibration. Not inexpensive by any means.

[Breakaway]

herez ware we r at jusnow.... fine tuning the inside


a lil picture i made of her about 20 years ago

At first glance, Bruce, I thought you painted a desert landscape scene on the inside of the transom. Looks like sky and mesas in the background, flat sand in the middle, and perhaps a riverbank with some greenery in the fore.

Maybe just clear coat it?

Kevin


Sent from my iPhone using Tapatalk Pro

[wizbang 13]

[P.I. Stazzer-Newt]

Broos, I can see nothing of use in this post, it seems to be a link to something in a Gmail account....

[wizbang 13]

merci...tech foul i guess .it's just a few pics of where we are now, no biggie

[P.I. Stazzer-Newt]

OK, perhaps some other time.

[John B]

Sooner'n later though.

[Paul Schweiss]

thanks chaps....I may go back to the bigger/tighter fitting prop later then ...after a lick with a file. (this on one of my own boats)

I would second that motion. When I was at San Juan all of their lobster yacht models had tunnels. The props were 4 bladed ZF Faster's which were progressive pitched, and they were all over square to absorb the large horsepower engines, the SJ48 wheels were 26" x 35". They also needed to be computer balanced to run right.

They had no more than an inch clearance, which was part of the efficiency of a good tunnel design to increase thrust, at any rate all of the models reached 37 knots WOT. We also bonded noise abatement tiles on the tunnel to reduce noise. Gregory Marshall did the lines and tunnels of the first San Juan 38.

I re-powered a Penn Yann years ago, replacing the big blocks with Yanmar 315hp diesels, and in talking with the owner who had gathered some information from Penn Yann, keeping the prop close to the tunnel walls increased their efficiency, and the 4 blades reduced the noise slap of water on the tunnel. He also said that when Penn Yann was developing the boats, they experimented with a variety of entrance shapes to the tunnels and actually used clear fiberglass sections so they could observe if they were reducing air bubbles which caused bad cavitation to the props.

[wizbang 13]

The Puttputt lives!!
Hours of motoring , she is doing fine.
Home made "cutlass "bearing holding
Prop bites the water instantly, no chopping at bubbles
The prop is a spare from an old 40 hp merc, 13 inch pitch
Insulated box
the yellow stack is now a novelty prop ! no more burnt fingers




She sets in the water as nicely as she sits on the rocks. We were afraid she might be far out of trim , between the heavier mill and the loss of bouyancy cut away in the tunnel.

[wizbang 13]

[Breakaway]

How's reverse?

[MoePorter]

Thanks for the update!

[wizbang 13]

How's reverse?

yea, um no
not so much,but we expected that

[John B]

Fun.