35' cat concept for the inside passage.

Hi Boston,
Looking at your 36ft cat, - - recognise that my 40ft cat has a pair of 20hp, 772cc, 3cylinder engines and is about 80kg for the naked, (with bell-housing), Kubota, plus more for the gearbox etc.... 144 kg includes all ancillary attachments, gearbox, drive leg, loom, exhaust system and so on.... Less than 50 hp each should be more than adequate and do not put turbo, as the extra heat dissipation and complexity is not warranted - think and apply KISS principles....

A bigger engine means that you have to push the moving parts that are excessive to application as well as the static weight penalty... Enough is enough... To add a reserve 20 to 50% will not push the boat faster as that is governed by the design limitations and is a penalty at all other times... Select the engine gearbox carefully based on weight then maintenance/parts and design around that...

The inline gearbox also has the thrust bearing, so the shaft load is spread via the gearbox mount and the engine block to the engine beds, I have a feeling, (no research), that inline may be lighter...

What for 125 hp? - - unless you plan hydraulic power-distribution to the 2 shafts - that technology is quite robust and allows the single-engine placement wherever, - but with potentially messy hydraulic lines....

Weight up forward ? drinking-water, toilet, black-water, batteries, mains-power-inverter, battery-charger, RO-Watermaker, fuel - careful as port and stbd balance needs to be considered... It also helps with hull efficiency to have a fine entry below waterline & widening fairly rapidly for 'wave buoyancy'... There are a lot of issues that make design considerations for a cat very different from a mono...

 

meh still looking for the right engine, but rest assured it doesn't come with a tag over 1k, and its almost certainly out of a popular car. I'll shaft it to two props and optimize it as best I can, shaft can double as the flywheel maybe, but if I end up paying a slight weight penalty over the million dollar model, so be it. The fuel cost is extremely unlikely to make up for the weight savings/cost over time. VW diesels are expensive or at least they are over here. Mercedes are a dime a dozen and parts are much cheaper as well. The International is the cheapest and the most reliable but the heaviest, so I'll probably end up going with one of the smaller Mercede's regardless of the few hundred extra lbs. Its just not worth the 10k extra to save a few hundred lbs. I'll make it up somewhere else and stick to my 6ton goal.

Richard suggested two 30s If I remember and that seemed about right. No clue I'm just looking at engines Mas, eventually I might, with a little luck, find just the right one.

 

lmao.
But just find a car wreck, CDK has laid out here http://www.boatdesign.net/forums/diy-marinizing/marinizing-vw-turbodiesel-engines-19118.html
what to do after that for the 1.9 engine, which appears to be one of the diesels of choice for this route.

 

I'm pretty well connected with the wild world of mechanics and parts. My truck is pretty well known around here for being the Mad Max machine it is. I can get a descent engine no problem, I'm not convinced the VW engines parts costs and availability exceeds that of the Mercedes 602. Or any of the Mercedes engines for that mater. I'm most definitely open to suggestion but being a gear head from way back I'm likely to go with cost of maintenance considerations primarily which to me includes finding a new rotating assembly from time to time. Just a cursory look shows those VW diesel engines at about 5~6x the cost of the Mercedes. I could get a factory crate block on the Mercedes but same same on a VW, fat chance.

I'll definetly go read that thread tho, might pick up some good stuff over there, ole CDK is a pretty sharp guy.

 

A single engine and hydraulics or a pair of engines, do not forget the thrust bearing - which will probably mean a PAIR of fairly new MARINE gearboxes...

On a cat, with the screws centred on each hull, counter-rotation is NOT necessary... You may like to consider 'sail-drive' legs as they come with direct engine connection, hydraulic or electric motors - whatever your 'poison'....

Be very careful of the thrust as I notice that some legs have 4 bolts and NO longitudinal reinforcing, and a stray small log will "Rip your bloody leg off"... to misquote a signature quote in a popular Australian kids TV show "The Aunty Jack Show".....

http://www.youtube.com/watch?v=KnEOr1MgwTM

http://www.youtube.com/watch?v=KnEOr1MgwTM

 

nah I got a plan for the drive legs that will preclude the need for thrust bearings beyond the drive legs themselves, that and duel trannies or any of that stuff. Going with a v belt drive system off a shaft. Shaft is the flywheel. Multiple belts and using the lower units of some long stemmed outboards. Should end up smelling like roses. Its a subject for a whole other thread though cause its pretty far off of the standard set up.

briefly I'm thinking of one engine, although as I keep saying, nothing is set in stone. There was a great thread in here somewhere about v belt transmissions for forward and reverse. I'm in, need two of them, thought it was a great idea. Then I want to shaft to a connecting rod that goes from one hull to the other. Might use a pair of light weight pumpkins for the connections as they go with the drive shafts so nicely. I've modified a lot of drive shafts in my days. Clutch at the first pumpkin so I have the weight of the shaft as my flywheel. after that its a pretty simple V belt drive set up onto a pair of lower drive units. I'd think it work like a charm but I'd have to build one first and test it for a year or so before I'd trust it. Kinda like what I'm doing with the truck. Which passed with flying colors by the way.

haven't got it all figured out yet but intuitively it seems like a plan

cheers

 

Can use the OM602.961 and the newer ones are the same internally iirc and will weigh about the same.
But the 190d 2.5 aren't nearly as common as the OM617.

 

hmmm I thought it was the other way around, my bad, I'll have to look into my local availability on either and see what the going rate is. I been meaning to buy an old Mercedes diesel anyway, keeping an eye out on CL lately, and my old grocery getter is just about done for, so its high time I get done with the truck and start the boat engine. Even if it is still in a car.

thanks
B

PS got that old 7.3 firing up first time on even the coldest of mornings, time to see if I can do the same with a Mercedes.

 

Ok seems like your set on the mercedes for a number of reasons, and the HP is about right for the entire boat off 1 engine... SO, where are you going to mount it and how wide is it?

 

working on it, specs seem to be eluding me at the moment. I did just find about a half dozen of them for sale just in Denver alone, and more than that if I just wanted the engine.

Depending on the factory crate cost I might just consider that instead of used. My bet is about 4k maybe 5 but will have to look into it. I've got a parts shop Ive been dealing with for oh say 25 years, so I might even be able to get it at 10% over cost. Thing is I need another car anyway. Might as well get familiar with the engine as well as develop a parts inventory. Might come in handy.

I'm not set on anything but I've been looking at the Mercedes engines for a while and it just seems perfect except it might be a little heavy.

 

As an aside, providing its not too wide and we CAN fit them into the efficient hulls... if you use 2 of these engines, you could have a reasonably efficient cruising speed above 15kts if you wanted to, and do it reasonably efficiently...

Reason i say this, is that you seem to be able to get these engines very cheaply... if thats the case, then its probably cheaper, easier, and not much heavier, to just use 2 of them rather than a complicated drive system to run off 1 engine... thats what i would do if i could get engines for $1000...

 

Hmmmmm hadn't really considered that. Still would want to use V belts though and keep the thrust off my engines. I can buy a 300D, the whole car, for under 3k and I just sent a friend of mine a query on one of those OM-617 crate engines. I can't picture it being more then 5k from the factory or 1k from the yard, probably more like $500.

I about died when I saw the cost of those VW diesels, who in the world pays that ? Someones got dollar signs in there eyeballs.

man specs for that engine are torturing me. Its like some kinda industry secret or something. Oh well I'l just go measure one next time I'm out at the junk yard.

 

well that only took an hour

but still not sure how wide it is

here's a great example of what a secret this info really is

http://www.peachparts.com/shopforum/diesel-discussion/203873-om617-dimensions.html

Mercedes sure keeps in under wraps ;-(

 

I just scaled it off my computer screen from a schematic i found (no dimensions shown in the drawing) using the published bore and stroke dimensions as a scale, and i get roughly 600mm wide X 700mm tall inc the sump for the turbo model... if you take the turbo off the side and perhaps plumb it round the back or get rid of it etc the width will come down to around 550mm (outside engine mount bracket edge to edge)... thats roughly what your looking at... i have no idea how much clearance youll need either side to be able to work on this engine tho... would 10" either side be enough?

 

well thats in the ball park, apparently this really is classified information I have discovered that the oil pan in 14.5" wide which means the block is unlikely to be much bigger than 24 but I need to know the width with the standard manifolds on it so I can be sure and have enough room.

Maybe if I just drop a note to the German gubment ;-)