I'm about to put my boat back together after a 2 year layup. The engines are 540's, 700hp@. It was winterized properly and oils changed before layup. I am guessing that I will have to drain the fuel tanks, change filters and pull carb bowls before attempting to start. My bigger issue is I need to re-install the extension boxes and drives and I have never done that before so I don't know how to properly seal them, any torque specs for the transom bolts etc.. I have new foam seals but should I also use any type of sealant on them? Any more advice would be appreciated, THANKS!

I am not an expert by any means , but I would not put sealant on the factory foam seal for the transom assembly . It doesn’t require sealant . I made the mistake of saying “ old boat , I’ll put a little 4200 on there “ That was a mistake , it made the seal a slippery mess that wouldn’t stay in place . So I tried again and put a little 3m weatherstrip adhesive to hold it in place on the transom assembly . It worked great ( I read to do that somewhere on here ) Good luck

Which drives ? Which boxes ?

there is a sequence that needs to be followed and i believe 3 passes until final torque.
the boxes would be torqued the same sequence and passes to the transom as the transom assemblies would be,
then the transom assemblies to the boxes would be the same.
think the bravo is 25 foot pounds.

i have the specs, sequence and so on for bravo and will gladly look it up and post it if thats what you have

no extra sealant think there is a gasket for the box but have to know what you got.
i.e. the speedmasters used cork and either cp or hardin have rubber for the bravo types

what work was done to the boat? What engine mounts ? Remember alignment is critical !

Stellings boxes, Bravo HP Transom assemblies, Imco SC drives, engines 540's/700hp@ on rail mounts w/ driveline shafts.

Transom assembly torque sequence.

Transom assembly torque.

Driveshaft flange torqe.

A pic from driveshaft alignment instructions

A pic from driveshaft alignment instructions


the drivshaft alignment instructions are about 5 pages, it looks more time consming than hard, but it is very important.
I would buy service manual 39, it's a 7 book set.

manual 39 for instructions sequences and torque values, and the mercury installation filter for dimensions etc etc is how i put my boat together. Well sweat, stress, lots of notes, drawings, colored pencils for flow charts and wiring diagrams along with hours of discussing the theory with myself all went into it.

https://www.mercurymarine.com/en/us/...tion-drawings/

this is the mercury filter, a small block is a small block, a big block is a big block,
all kinds of good dimensions here.

You might want to reach out to some racers / riggers who can help you with your set up, very cool by the way driveline stellings and rail mount.

see those specs on the driveline +/- 1-3 degrees, but the flanges have to parrellel in the vertical and horizontal.

Put some pics up this project
The rear engine mounts, are they between the engine and flywheel cover, or are they bolted onto the bearing carrier.

Thanks for your replies and info. All of this will be very helpful. Kurts Performance Marine / Bandit Racing in Brick NJ originally put the boat together for me about 7 or 8 years ago. Since then it has gone thru many changes including 540's ground up builds, 700 hp@ on N/A carbs and the drive lines etc. We moved the engines forward a little and lowered them down into the hull to reduce COG. Playing with prop CL which is now at 2 1/2" above the bottom. Had the boat to 118 mph so far, heavy boat 1988 Hydra Cat. running 36P 4 blades and need more prop, running up on 6K rev limiters. Lunched drives and ran out of patience and money 2 years ago. Time to put it back together or get rid of it. We will try to put it back together. Rear engine mounts are using plates I'll get some pics up when we get started. Thanks again!

safe driveshaft angle with stellings ext box

Above, some good math from 3 very good sources

Once again, very helpful info, Thanks! Since moving the engines where moved forward and down my shafts are more than 24" long which decreases my angles quite a bit. I have run with this set up and angles for several seasons with no issues except for tearing the splines out of one of the coupling flanges. What a nightmare, part no longer made and I had to find a machinist who could make one with Mercury splines. I had him make me 2 of them so I have a spare ay almost $1000. a pop. Whats a few more thousand right?