has any one put a diesel in a 20' cig? my bert runs a 230hp diesel about the same lbs as the 454 that it came factory with my boat... the same motor is made with 410hp now.. the two diesels in my 14,000lbs bert will give me 26knot at 3600 rpm so in a 20 cig be a lot faster. and the 410 hp be nutty.... there motors are marketed with out drive so seems like it work....

Larry,

I'd imagine you'd get a ****load of torque out of the diesel, as long as the curve is correct, that could be a very interesting setup!

Harry

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finished the stringers and transom's s-glass lay up today tomarrow I will grind & kevlar the engine compartment and rebuild the transom lip where the hull meets the deck. Then I can, at last flip the hull to strip and fill the hole... also I re cored the engine hatch and the front hatch both there foam cores were filled with water,,, the front hatch is now divinycell and the rear engine hatch is nita core all the work to day was in 24oz roving and epoxy,, I saw no need to use kevlar for hatches as they do not bare a load... the transom needed a lot of glass to fill the holes so went with s-glass over kevlar as it would have been a pane to work with if solid and just a waste,,,

Today I did not end up getting to finish up the last kevalr lay up.. I ended up rebuilding the transom lip where the transom meets the deck cap and the part of the deck cap that was cut out,,, I also started to fill the jet drive pick up hole and replaced the stringer reinforcements that had been cut down... one more day of grinding and one day of kevlar I think and I can flip the hull and deck to strip the paint....


I have been giving the diesel idea some thought I can get a 250hp to 450hp hi rpm diesel like a yanmar or a merc. it be about the same lbs as a big block chevy and be the same torque as a 350hp to 800hp gas motor pending on the displacement or the diesel... a modern diesel spins at 3600 rpm and wat is 38000 rpm also close to a 454 about 600rpm slower.. lots of off shore boat to day run diesel alto non this small that i have seen. but a 2:1 drive a larger prop can make the world with a diesel... I like the idea of a reliable boat that can still move, can use the same fuel as my bertram and may be the same engines make parts I little less of a pain in the but needing only one set of spares..

just a note on proping a diesel... my b35 ran 350hp 454's the boat had 4 blade wheels and did 19k at 44000, my merc diesels are 210hp so 410 total and spin at 38000. now lauderdale prop tells me I will make 24 to 26k running the same 4 blade prop and same pitch... most boats are repowered to the hp the boat had and this means shafts props rudders and so on need replacment... this was done due to the fact that for years a diesel motor was a marine dump truck motor! and spins at 24000 rpm and the hp was need to move the boat on to plane but spin all that water faster and you end up needing to only fallow the torque curve,,, now were talking about moving a fishing boat that was built to only move 26k wat and 36k can be done but also can't be done with out keel walking the boat and burning crazy amount of fuel....

I think a diesel would be a cool idea, but I find it hard to believe the weight would be even close. Unless you went with an aluminum block like some of the old detroits. I'm no expert though, so I could be way off base.

Have you seen this little Donzi?

http://www.donzi.net/forums/showthread.php?t=61317

What drive do you think you will use?

love to git my hands on a drive like the one on the donzi....

mercruiser's 3.7L, 4.2L and 4.7L diesels are all 300lbs heaver then a mercruiser 350ci according to mercury,,,, all 3 motors are the same every thing, other then bore, stroke, c/p ratio, computer, and turbo all weigh the same all will bolt to an out drive bravo 1, 2 or 3...
I do think the engine is 6" longer then a 454 with water cooling, may be too long...

in a searay sun dancer the 250hp diesel did 1.5 knot slower then the small block mercury the two boats were the same other then power... so maybe the 450hp diesel will move 3 knots slower then a 450 hp 454, who knows...

there is some thing about the sound of a big block. I am just thinking about power & drive at this point.... and have know real plan,I have been looking at moded bravo 1 and blachawk drives like the idea of a surface drive, a 20' foot boat seems a bit small for one.......

A couple diesel engine ideas for you a company named Penninsular engine sells a 6.5 that happens to be one that we manufacture where i work i think he gets around 340hp out of it . The nice thing about it is it mats up to some of big cev parts and i thank its not much heaver.Another nice engine is steyrmoters they do a lot of marine work you can call Rich Alley at 850-784-7933. the only thing you my want to keep in mind your 20 handles so will at speeds between 70 and 80 and i dont know if a diesel will get you those speed l

what kinda HP do you think a gas engine needs to move a 20 foot cig 70 to 80mph................ maybe 550hp....