Hey guys,

I'm looking to get some input from some guys who run inboards. I have a 25 whitewater center console that I fish and dive off of and right now it has an 1996 OMC 454 with some 800 odd hours, boat weighs about 6500lbs loaded. I am replacing the fuel tanks right now and I have been rolling around the idea of pulling the 454 and putting in something new and better on fuel. I was looking at the new mercury 350 ECT inboards but then a few guys have been recommending the reman 383 mag MPI from mercury. Cheaper price and more ponies than what my 454 is putting out currently (somewhere in the neighborhood of 310 if Im not mistaken). Anyone out there have any experience with either of these on a inboard straight shaft setup? What kind of bump up in fuel econ should I expect to see? Its hard to find any manufacturer performance reports out there with the power setup that I am looking at. Thanks again.

https://www.youtube.com/watch?v=lziJUepBkdY

There is no replacement for displacement. Looking at standard BB to standard SB (stroker) I would go with the BB every time. Since your repowering I would go with a 502 crate motor and not go with brand new drop in, because you would be looking a smog stuff. There are several folks here which have some drop in ready blocks on the swap and classifieds

http://www.michiganmotorz.com/base-m...01-p-3551.html

Looking at the boat test report, I think the 383 would be a good choice

Closed cooling ? This the omc 454 thats a gen 6 vortec with a holley carb? Or gen 5 steel timing cover?
When gas was double of what it is now, swapping from the holley to the mpi injection was a popular operation to take 10-20% off fuel consumpion.
That 383 will come close to matching the peanut port bbc at the upper rpm , and take up less space ,but wont have the cruising speed torque of a 454 .
Gen 5 454 was offered with tbi injection, simple and can help a bit with fuel usage , but still old school

Closed cooling means everything when the subject of .30 over vortec small blocks going offshore comes to play

the current motor close cooled I assume, if it has lasted this long.

800 hours is nothing on that motor.

Hey guys thanks for the replies! The current 454 is raw water cooled and has a rochester carb that the previous owner put on it. I haven't made up my mind yet on which way to go. I'd like to get as much input from experienced inboard guys as possible. The biggest thing I am looking for is the best fuel econ I can get out of a gas inboard, and if at all possible maybe a slightly faster cruise speed. With my 454 I cruise at around 24knts right now, WOT at 32ish. Not too concerned with top end, just good cruising fuel consumption and speed.

Ok just call me old school but I would like more cubic inches working less than I would have smaller cubic inches working harder to achieve the same results. That is one reason what you have has lasted so long. Do I want my Clysdale pulling my beer wagon or a thoroughbred pulling my beer wagon for the long haul to the party? Good luck. Lot of good info from guys on here.