Need trans for small diesel

I've made the V belt tranny you describe Marco, previously and it worked, though it's not a very neat way of doing things. I do miss the "chirp" it would yell, as I lowered the tensioner back down in reverse and the garden tractor tire took up on the shaft mounted drum.

A no reverse unit, just isn't worth considering, weight is an issue and an enclosed gear box, with marine grade internals is mandatory. I can find lots of transmissions for bigger engines, but below say 25 HP, it's mild steel go cart stuff and other convoluted crap with pot metal and plastics.

 

You made one like that? Hum ... I re-invented the wheel, ha ha, its not the first time. I also invented the HUD speedo for cars, oh well, I think I was born too late.
Did you try your luck on e-bay? Not much on the US side but lots on the UK where they seem to favor small diesel engines and small boats in general.
If the price is right, and the gearbox does not sink the boat, it does not really matter if it is for a 50HP engine.
After all mechanical gearbox overstate the power severely. Take the PRM80 for example it is sold for 47HP yet I wouldn't put it on anything bigger than 25.

Here are a couple of cheap one.
http://www.ebay.co.uk/itm/BORG-WARN...at_Engines_EngineParts_SM&hash=item1c3e4d437d

http://www.ebay.co.uk/itm/PRM-Marin...at_Engines_EngineParts_SM&hash=item338c7d9024

 

I have a very good tranny from a Volvo MD 7 .

It includes the clutch and about a 2-1 ratio for Fwd and Reverse.

It has a setup that can be seen on the Volvo engine sites where the engine has a flat plate with 3 ears , the tranny has the same , and a rubber biscuit has 6 slots that allow the coupling.

Would be easy to use as the tranny has the thrust bearing already built in.

$500 US, plus shipping, or drive over to Ortona and pick it up.

 

A transmission from a front tine roto tiller might work for you. They can take some pretty serious abuse and keep working should be lots around with blown motors. Belt drive input shaft drive output.

 

Sorry I see its already been discussed. I should have read all the posts first but I still think one from an old tiller would be fine I had one f-n-r made out of cast iron, all it needed was a belt tensioner to be able to release pressure and than the shifter was right on the top of the case front to back shift pattern.

 

gas golf carts have transmissions with reverse.
If one wasn't married to the diesel, a two-stroke can be run in reverse,
making its already lighter weight advantage over a diesel that much better not needing a transmission.

ATVs have transmissions with fwd and reverse also, here is one:
http://www.ebay.com/itm/1996-Polaris-2X4-300cc-Transmission-With-Hi-Low-Reverse/111297368137?_trksid=p2047675.c100005.m1851&_trkparms=aid%3D222007%26algo%3DSIC.MBE%26ao%3D1%26asc%3D21235%26meid%3D5864671926754458712%26pid%3D100005%26prg%3D9374%26rk%3D4%26rkt%3D6%26sd%3D181339165507&rt=nc
Couldn't tell you what the gear ratios are.

One can also use a differential as a transmission with reverse, but you need to be clever. The MG Midget differential is small, aluminum and very lightweight.

 

The problem with rototillers and ATV trannies is they rust up fairly quickly in a boat. I used a garden tractor trans once and it rusted up very quickly, though it worked. I know a fellow that has a Volvo MD 7 tranny hooked to an old Atomic 4, but it's way to much tranny for what I need.

 

Don't quite understand how an ATV trans would rust when made from aluminum.

Why not use a variable pitch prop that can reverse, seems natural for a boat.
I understand they are very expensive to buy, but maybe do a thread on how to make one yourself?

 

A VPP on a 5 - 8 HP engine, really?

 

Didn't the inshore fishing boats in Norway and Sweden use VPP on low powered Sabb diesels? IIRC it was quite common at one time.

 

I do remember seeing a VPP for small craft years ago, but I haven't seen one in decades (at least 3). It's a good solution, if costly.

 

what about a generator on your engine and a couple of pod drives with kort nozzles. and a computer management system to make it more efficent.

 

Volvo MD 7 tranny hooked to an old Atomic 4, but it's way to much tranny for what I need.
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Those old Volvos MD 7 were 13hp at 2600rpm , and have as all marine trannys have the thrust bearing built in .

The reduction gearing , reverse and clutch are bonuses .

 

What about using a tiller or whatever tranny and getting it nickel plated or powder coated or even flame sprayed with Teflon. A number of years ago I was sandblasting and painting and we done some of the marker buoy's for the St Lawrence sea way with the Teflon flame spray. Or maybe even galvanized. No more rusting.

 

For any sort of small farm transmission the key word is old. Not much farming in Florida though. A tiller transmission is a better choice than a riders. Something green in colour or if it says John Deere even better, but stick with old. All your craftsman and variants are throw away machines. Use them for a couple years throw them away and buy a new one.