diesel transmission?

Trying to figure out how to make a low power diesel,like a kubota work in a sailboat(cheaply)I read something about using some sort of reduction gearbox,also wondering about that,trying to slow down the prop rpm?or the other way,spin it much faster than the engine rpm(seems like the later)wich i guess bolts up to the flywheel and use a shaft with a support bearing coming out of pipe,and a prop.Im not quiet as mechanicly inept as this thread makes me seem.But im used to just using a sailboat without an outboard or engine.This is for a trimaran for the south pacific and im told of glassy water with no wind.Ive tried reading about different drives,hydrolic and such,some ideas on low budget diesel setup(should interest many people!)help!

 

Well, since nobody else jumped in, I'll give you my 2 cents. A Borg Warner Velvet drive or other such marine transmission can be coupled to your engine and they come in various reduction ratios, and also provide reverse. Velvet drives are as low budget as you can get, costing about $1500 and up for a rebuilt unit. They're very reliable, but a little noisy (gear whine).

 

Ron, Dont believe all that stuff about glassy water and no wind in the south pacific. Sure, theres some of that in some areas, but dont design your boat to best case scenario specs. Even glassy lagoons hide treacherous currents in the channels, and weather can change drasticly and suddenly. Overkill in the engine/drive area is definately a good idea, even if you have to sacrifice some interior space. You will find that the cabin space is so hot and muggy as to be uninhabitable anyway, and you will be living on the deck.

 

If your boat has never had a inbord motor it will not be that cheap to put one in.the cheap way would be to stick a outbord motor on the back or 2 of them one on each outside sponsen.Kubota motors are very good though.A company called Universal uses them for there marine engines.To marinize one your self could only cheaply be done if you got a locked up or wore out universal for next to nothing to swap out the marine parts. And it would need to be the same sierise of engine. The bell housing on industrial motors have the wrong offset to mate up a transmition.and the exhaust manifold is dry.Other than those two things if you are slick you could make your own mounts,plumb in some heatexchanger off of some other motor,belt drive a raw water pump,and weld your self up a mixing elbow and you would have a marine motor.But what a pain in the arse.And for those little motors a mechanical gear box is used,usualy a hurth.Good luck I hope this helps

 

No you would still not have a marine motor. You have to change the camshaft, calibrate the injectors, calibrate the injection pump, change the flywheel or get an adaptor and add an oil cooler.

 

It would be a marine motor.It,s probably just a little terdy 3 cyliider for a blow boat.its not a high output performance diesel.I doubt they even have different cams and injectors for them little things there not turbo or any thing.they just use them for pumps,tractors,generators,or watever.The little chugger would spin a prop fine.a oil cooler is nice but not a nececity.For real though just try to find a used yanmar,that will be hard thing to find though.

 

Marine engines run at full load. An injection pump calibrated for other use will make the engine smoke and build carbon. Eventually the carbon will seize the rings, score the cylinders and maybe crack the pistons.

 

Runing with a full load

A small 25 horse power diesel engine will do what its told all day in a boat or otherwise. if the engine is proped to get it's full RPM it will hump all day or till it runs out of feul.If it is over proped and can not reach the rpm it is rated for it will smoke and get warm.We aint talking gas stuff diesels are tough and them little ones are the toughest.Not that it would matter but sail boats rarely see full throtel wide open usualy just burys the stern and goes no faster than if you backed it off

 

carlwun: Would you write a written warranty on your opinion? What difference do you see on a small or large diesel as far a rating of operation goes? Also, what happens if the sailboat engine gets run at rated HP for say 40 hours?

 

"Also, what happens if the sailboat engine gets run at rated HP for say 40 hours?"

If the engine was proped properly ,( or if overproped as most rational cruisers tend to do , and at least 10% or 300rpm below max observable rpm ) the engine will run till its out of fuel.

Shut downs for an oil change are helpfull tho.

Many tiny lawn tractor engines , KUBOTA similar Yanmar plug away at almost full load as refrigeration drivers in many reefer trucks.
They run 24/7 for the time it takes to get vegis from CA to ME , and do it for over 10,000 hours with very modest maint.

FAST FRED

 

Maybe this information that I copied from a dealers website will help in understandind why there is so much debate about diesel engine performance and use. I will post the link in another reply.

Ross in Bel Air



Marine Engine Power Classification:

B - Light Duty
- Boat Type and Duty:
Light craft for recreational, commercial, or military duty with frequent speed variations.
Examples: Pleasure Craft, Chartering, Passengers Transport, Fast Patrol Boats, Police, Coastal Guard, Rescue, Special Corps.
- Engine Duty Cycle:
Full throtle operation < 10% of use period, cruising speed at engine rpm < 90% of rated speed setting. Maximum usage = 1500 hours per year.
C - Medium Duty
- Boat Type and Duty:
Work boats, military, light fishing boats, taxis, short distance seasonal passenger transport, fire-fighting boats.
- Engine Duty Cycle:
Full throttle operation < 25% of use period, cruising speed at engine rpm < 90% of rated speed setting. Maximum usage = 1500-3000 hours per year.
D - Heavy Duty
- Boat type and Duty
Fishing boats, work and passenger transport with the possibility to utilize the engine continuously at maximum rating.
Examples: Fishing boats, work and passenger transport, and towboats.
- Engine Duty Cycle:
Maximum rating utilization up to 100% of use period for unlimited hours per year.


Marine Engine Power Classification:

A 1 - Short Range Fast Pleasure Service (High Performance Pleasure Crafts)
- Boat Type and Use:
Pleasure and military boats with a gliding hull and high speed or half-gliding and displacing pleasure hulls utilizing maximum power for short periods alternating with extended periods with a speed lower than maximum speed.
Examples: Pleasure Hulls, High Speed Boats for military or state bodies
- Engine Utilization characteristics:
Maximum power utilization limited to 10% of time, cruising speed with engine rpm < 90% of calibration rated rpm. Use limit = 300 hours/year.

 

link to engine ratings :http://www.maesco.com/products/mar_prop/mar_pleasure/mar_pleasure.html

 

Of corse i would give no warinty on some used DIY marinized motor.If the motor was new i would see what the manufacturer,s rules are but i doubt they would want to play ball.They don't have to it's all about the $ with them.The difference is see with the motors is not to mutch the size but but if they are jacked up or not.A non turbo motor just wont need the good valves,pistons,con rods,push pods,piston oilers,feul coolers,big oil cooler,big cam,yada yada yada that a tubo after cooled posibly Kompresored engine needs.wether it's in a boat or not.The low out put motors are made to work hard all the time and like it.The high out put ones make more power but don't like it.The hot rod version of the same motor even with all it's goodies won't last as long even if you don't push it hard all the time.A motor in a boat just won't last as long usualy as one on land fact of life.A factory built marine motor has nicer stuff on it and slicker plumbing and often a oil cooler.I don't like home built abortions because they are ugly.But if you can stick any motor in your boat and get it to spin the prop and stay cool you got your self a boat motor.And a little natural 3 or four cylider motor likes a good load.It's a diesel.

 

"They run 24/7 for the time it takes to get vegis from CA to ME , and do it for over 10,000 hours with very modest maint."
Thats rite and it's beter for them than puting around and shining up the cyl walls.Those japanese small diesels are made for one reason from the start.That is to work like dogs hard all day.Most of the big ones were made for trucks.The big truck motors have there idustrial versions and and do it well but all the small one are for work not the high way.The huge or exotic 1000+HP engines are some thing i just get to drule at while i am in the bilge fixing the genset

 

Stationary engines ( reefers and gensets) are governed to run at a fixed RPM. You are comparing engines set up for very different application. HP rating alone is not an indication of how the engine will perfom. The torque curve is more accurate. If you look at the graphs of torque curves, the flatter the better. Also, in the HP graph the engine with most developed area will outperform on with higher peak HP.