1981 Nautique on a diet...

Same bell housing bolt pattern so it'll bolt right up with a new damper plate for the different splines like you mentioned.

It seems ;like 135 pounds is pretty heavy on the B/W with the bell housing and cooler unless you're weighing it with the mounts included or you have a cast iron bell housing

I think I'd call Joe at FFI marine and see what he might have for a used output flange and a new damper plate

Here's his contact info from last year

FFImarine wrote: Hey guys! We have moved to a new location as of June 1st new address is 1669 w130th unit#403 hinckley oh 44233 are phone number is still the same.(330)273-8291. As always we will be here to answer any questions you guys might have day or night so please don’t hesitate to call. I’ve been working for this company for over 16 years and I’m proud to say that my hard work has payed off cause I Joe D’Amico am the new owner of fantastic finishes marine. Please spread the word for me guys and thank you for reading

And as far as the transmission tester, it kinda morphed into a transmission/raw water pump/ alternator spinner/tester too with a couple more easy to make brackets.

It keeps my simple mind easily amused   

MrMcD - thanks!   I am pretty confident it will go north of 55 and as you note the Corvette equipped with the 383 would hit 55. My boat is much lighter and the engine has a more aggressive cam that will open up the top end so it will be fun to find out :-)

Mark, it has been a lot of tinkering which I enjoy. It runs great, although not broken in so top speed is not known yet, but given its around 500 hp and tips the scales at 2175 lb and previously at 100 hp less it would go in to the low to mid 50's, I expect it will do a bit more than that now. RPM is 3400 for 36 mph don't know what peak will be, it pulled 5,600 prior to the aluminum block and bigger cam (.560" lift) so who knows at present. It really squirts forward when the throttle is cracked open and the spool up is really quick a lot due to very low piston / rod / crank / flywheel inertia and overall light weight. So yes, it is a beast:-)

It's actually brand 'Bu' but I stumbled on the weight saving and transmission thread so I thought I would share my story. The real goal was to improve the wake via mass reduction so I was here poking around for a PCM 40I trans. It also tracks great in through the course, I was wondering how that would go. I do spent lots of sets behind a 200:-)

Yes, old style SBC. It was challenging to find a block, ended up going with an aftermarket new one from Speedmaster. It has all the production attachments which others do not. Aluminum flywheel is fine, no issues and that was a concern as I built this thing up, going in to the unknown but idle quality and accel is great, I also have a pretty aggressive cam but it idles like a purring kitten and runs like a scalded cat so happy with results. I did debate the whole LS option, doing a fair amount of math it looks like a minimal SBC is lighter in the end mainly due to the whole accessory drive setup. I did the upper end years ago before the LS stuff was even on the market, so that helped the decision to stick with the old school SBC. An LS-7 would make one heck of a package:-)

Gotta ski - it was a step wise process, started with a basic 94 Merc all iron engine, swapped heads to 'fast burn 385' and needed an aluminum edelbrock manifold to accept bolt pattern. Added Stainless Marine aluminum exhaust manifolds with 4" outlets so then I made my own exhaust tubes and SS 4" tips (that first hole is the hardest to drill, after that one a lot easier:-). Ditched the circ pump for a simple stainless tube and an automotive style tstat housing which shed ~30 lb over all that complex plumbing. Fast forward to now and once the engine was on a stand for a rear main replacement, I found an aftermarket aluminum block which then led to 383 crank, 030 Mahle pistons, aluminum flywheel and a pretty trick camshaft, so a $2 main seal suddenly got expensive, LOL.   Engine mounts all stayed the same, used same distributor so really the major fab work was exhaust and raw water inlet hoses with the circ pump delete. As I previously noted, looking for a lighter trans for another step. The rest of the boat has gotten a pretty good diet, made several carbon fiber parts and moved the fuel tank to move CG forward so total wt, reduction is 475 lb.

What have you done and how are your results?

DW1-nice!

Sorry I forgot about this thread,

Have updated the first post to current.

I've moved everything listed over to a '82 SN 2001, and will continue shaving.

The PCM 40i install was very straight forward. The drive plate is different, otherwise straight bolt up. You may have to redial the aluminum cradle (if so equipped) because the mount holes will be slightly different. The mounts transferred over. Only other detail is the shift cable bracket is different height. Shaft coupling is the same too.

depending on budget and how much engine work your doing could you do a 347 stroker rather than the 351W, its something like another 50lbs

Keno, thanks and yes that funky symbol works on those other sites. Nailed it, LHR Chevy powered 'vessel' and you might consider playing the lottery this week, your guess is spot on. Just to ensure I am in good standing here, my ride when I hit the course is a 200:-)

Thanks for the comment on the 80i & the various links, my early stages of learning the details on the PCM tranny's.

@Keno: Thanks, appreciate the link. I would be shopping for a 1:1 version of that box, I will have to learn the naming configs.

@MourningWood: How difficult was the transmission swap? I have done similar weight reduction on my ski boat with excellent results. How satisfied are you with your project?

Why reinvent the wheel- just copy the Holman Moody method. Later on a circulating pump was added to better the cooling but this was the minimum

MourningWood wrote: making a cooling system utilizing a crank-driven RWP and eliminating the engine-mounted circ. pump.

You could look at a 351 Indmar cooling system setup instead of "making your own".

The housing in the link is available these days and replaces an Indmar setup using a crank mounted pump.

No funny routing of hoses or anything

link

Have begun futzing around with this '81 Nautique in a way that I've always wanted to do.....weight reduction.
Nothing fanatical, just see how it performs at around 1800 lbs.
First up-drivetrain. Beginning with standard 351w and 71c BW trans:

Edelbrock aluminum heads: Shave 42 ib.s total
Edelbrock aluminum intake: 31 lbs.
Aluminum front timing cover: 10 lbs.
Transmission swap to PCM 40i: 47 lbs.
Battery: 27 lbs.
Exhaust manifolds: 61 lbs..
Crank-driven rwp: 8 lbs.
Thermostat housing and hoses 7 ibs.
Starter 9 ibs.
Water circulation pump 11.5 lbs.
Alternator brackets 2 lbs.

So far: 255.5 lbs.

This winter: motor box/swim platform/seat bases/floorboards.....

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