Big Block Billy

I'm going to repower and try to sell a 1975 25' Nova with Twins. Boat has 302 FORDS. Boat did almost 60mph. 1 motor seized 1 spun a bearing. Have all parts incl. new manifolds. Also know where 4 complete motors are for a few hundred. Alpha's are already rebuilt. I really want to experiment by making up 400SBC motors. Has anyone done this? I have Dennis Moore's books and have all the parts incl. (2) 4bolt 400's. Is this too much power the boat? Will it make the boat chinewalk or unstable. I'm thinking of about 400HP EA and maybe 1.32 upper gears. Do the 400 steam holes pose a problem with salt water and blockage due to rust? Basically a joint venture is what this project is. Last summer we resurrected a 1982 38' Scarab incl. building and installing the port engine. I could put 350's in the Nova also. I'm aware of the holes in the heads on a 400. Maybe I have a hole in my head ! Or My head in my hole!!!
Anyway I'm not too crazy about Ford motors and the outdated accessories. Thanks For any help BBB

cdscarab

BBB,
I helped a friend put a 400 sbc in a 23' formula sport cruiser 2 summers ago and despite the rather mild cam, it really brought that 6000lb (gross) boat to life. Added about 10 mph to his top end. There are several things to check though, 1st make sure the heads are drilled for the steam vent holes, 2nd make sure the drives are in very good condition, 3rd use a good center riser exhaust system, 4th if you are going to use Qjet carbs, make sure to epoxy the machine plugs (2?) on the under side of each carb to prevent fuel leakage directly into the intake. I saw the question of salt bothering the steam vent holes answered once before here by someone who said that it hadn't bothered his motors, of course a good fresh water flush after each use would be good insurance against touble. As for the drives, my friends was in less than A1 condition & that 400 ate it up & spit it out. Which leaves the carbs, his was leaking fuel through those machine plugs and in conjuction with a restrictive exhaust cooked all 8 stainless exhaust valves, discolored the iron around the valves almost ruining the heads, and even cooked the rockers. Small items, very expensive consequences.
Despite the initial problems, I like the motor and would do it again with the proper precautions. Strong motor, lauches his formula as hard as my stock 7.4 does my 21 scarab.

cdscarab

BBB,
One other thing, if you looking for 400hp from these motors, I would go with a better rod (5.7") than the stock ones. Something like the new chevy stroker rods or the aftermarket H beam rods so you won't have any clearence problems with the cam. And then use a good roller cam. Should make for a very strong motor.
I believe one of the other members used Vortec heads on his 400 with excelent results. You should put the question out there if your interested.

Big Block Billy

Thanks CDSCARAB ! I have a 21' Citation Laser(Baja hull) with a 454 that kicks @$$. I'm going to sell it, Alpha 1.32 drive stays together. The real issue was the propshaft rpm and pinion stress with the 1.50 gears (found out later!). I had blown up several 1.50 drives and ended up putting a bravo setup on it brand new out of the box. The Formula 242ls I now have had the 1.32 alpha on it when I bought it with a siezed motor. Knowing that I'm already at a loss with the "Baja", I decided to put the Bravo on the Formula and made the other boat Alpha again . I always wanted to play with a 400 since Merc. never made them as a boat motor. I figure it a great power to weight ratio and reliable h.p. with pretty much stock parts. Thanks BBB

Offshore Addiction

no 400's in salt!!

cuda

Is that because of the siamese bores?

Offshore Addiction

steam ports plug up and blow head gaskets!

Big Block Billy

Thanks Alot guys. One question remains. If I was to flush real good after each use could I get by with the 400's ? I really want to try this out.

Linster

You must use a Farria head gasket. Its the only one I could get to seal. If not you will blow a head gasket every season. You must drill the steam holes in that gasket. Car people block those holes and do not care. I changed head gaskets every season after finding them just to keep from having a bad day boating.

I had 400's for three years and found the following to work best after lots of $ and trail and error.

Steel heads work best, Merlin SR' s. A single plane Victor Jr and a Holley 750 Double pumper was much better that Qjet. A Linati 235 streetmaster cam was the best for power. Make sure you use a 140 thermostat. Dont waste time on exhaust, but I brazed a 3" piece of pipe on the riser to stop the reversion a 400 will make. Any welding supply can supply the 1 brazing rod you will need.

Big Block Billy

Very interesting stuff. I really am interested in why the 400 has more reversion. The boat exhaust tips that are on it are above the swim platform and are higher than the elbow outlets, unless the boat is underway. No wonder why this boat suffered water up the exhaust! I was told by many people to raise the X dimension, It might" kill 2 birds with one stone" . I want to play with this boat without spending tons of money(if that's possible) I like the Idea of brazing extensions on the elbows. I have a carbon arc torch that makes it so wonderfull to sucessfully repair cast iron. It really makes the heat you need. It's a shame that this is becoming a lost art and is little known to even some good weldors. I also use the nickel bronze rods. Thanks a million, Keep posting so we all can continue to learn more.BBB