Hi all,

I've just bought an Ocke Mannerfelt B28 and I'm starting to prepare to re-rig it from outboards to inboard.
Currently I've got a very good condition 8.2 BBC with a Holley 250 supercharger and various other trick bits giving it a tickle to get about 600hp.

I'm now thinking about changing to an LS based motor instead but haven't been able to find many comparisons. With the LS being much lighter and injected, I'm guessing I'll need less power for the same speed and it should be more efficient? They seem to be available as GM crate motors at good prices, where would be a good place to find one?

It'd be good to have better economy, but I am ultimately looking to get 100mph from the B28, will a LS motor stop me?

Any thoughts or opinions would be great, this is new territory to me!

Thanks,

James

me personally,,go to a junkyard and find a 6.0 truck engine..they make stroker rotating assemblies for them,the crate engines have cast internals from what i have read..anyways i would have one built to your specs,,low compression, about 8.5 to one stroker to 421 cid with a m3 procharger will give you around 700 +pump gas hp..

Go here > http://www.turnkeyenginesupply.com/ They have marine engines with Mefi 4

If you know your way around an LS, it's a great way to go. If you have to pay someone to build it/install it, then there are probably better options.

Like if you have to go to turnkeyenginesupply to get your engine, Id probably have someone put a big block in it.

Thanks for the replys guys!
Sadly over here there are no junkyards, and there definately aren't any 6 litre trucks! Probably should've reminded that I live on a small uk island called Guernsey!

I did a bunch more research into the subject last night and found it doesn't look like it'd be as straightforward as I hoped.
My thoughts were that I could just buy a lovely light ally crate motor, marinise it a bit (alternator, starter etc) and have a great, modern, lightweight engine. Seems that definately isn't the case!
Parts are hard enough to get even for a BBC here, let alone a motor even the US guys struggle to get bits for!

Seeing as I've already got a great Supercharged big block here I think I'll stick with that till I can get an Ilmore!

Look at Boatmad ,There is a p21 ( P21 inboard Thread )whit one in does almost 100 mph ,96 exactly ,its mine

I have done it and a friend of mine build ls engines for many years now in race cars and know exactly what can and what not and not very far for you ,in the netherlands !

You will really like the ls it push real hard and if you see the dyno sheets it will win from several BB only in the low end tq the win not always but you don t need that in such a lite boat .

Pm if you need info ,there where a few very good priced ls2 available a month ago maybe there are a few left .

cheers

Bor

You're thinking along the right lines. Here's my setup. 103 mph @5900 rpm so far, with another 500 rpm to go...

Drop me a PM with your email.

NICE !!!

this mine



in here



here are a few vids of it
http://www.youtube.com/user/phantomlspower?feature=mhee

Since you already own the big block I'd stick with that. Sell off the 250 blower and go EFI with a Procharger or Whipple for the better efficiency you want, and the extra power you're gonna need to run 100mph. I've run beside a couple of the 28's with SC'd big blocks and they seem to run and fly really flat and fast through the chop. The weight of the BBC doesn't seem to be a detriment at all whereas the light LS may effect CG adversely.?

C-Spray - PM sent!

Bor - Hi! I've followed your thread on boatmad with great interest! I don't know if I want to get that involved with an engine build again though!

Haxby - You're quite right. From what I've now learnt it seems it'd be silly to get rid of such a good condition 502. It did occur to me that they are known for trying to fly with the nose low, a lighter engine could very well upset this balance.

Sounds like I best play it safe and stick with the 502!

Cheers, James