bertram31.com

Ok all of my Diesel Friends...For a Variety of reasons, health and boat usage primarily, I am going to venture over to the dark side and repower my 31FBC with gas engines...35 years and have never owned a gasser, but I think being in the temperate climate of South Florida and my short hops to Swordfish country, I think this is an appropriate choice for me...Having said that, I would love all of you guys to please give me the pros/ cons and experiences of Crusader 454/350s, Crusader 454s High Output (Aluminum heads at around 400 HP and more torque, and 502s...I am going all Carbureted for simplicity sake and still have to decide if the appropriate gear ratio is 1.5 or 2/1....I am hearing very positive results with 454 boats down here that have 2/1 trannys; and Lauderdale Propeller who probably has done more Bertrams than any one else in the last 50 years swears by them for 31s...I hope this excites a lively debate as there are so many smart and experienced people on the site...Best wishes and Thanks to all in Advance...John

Look up posts from Pete Fallon.

If I had to repower today...the setup Pete had would be the direction I would take.

Moving forward to when kids get out of school and after I save a bit for retirement, it will then be the diesel route.


If I blew a 440 motor today...I have a spare, I'd swap out and keep going.
If I come across a diesel deal (read - if I can afford to buy and do conversion) that will be the direction.


My two issues with gas...having an ignition system prone to getting wet and crapping out. Although I have been very lucky.
Gas labors going up the back up swells , especially when loaded...maybe way bigger hp/torque gas motors, but at that cost it close to diesel territory.

You should do a search on the Blackfin site for 29 Models---much more discussion on gas options

My first B31 (Anna E.) was a gasser, and I had looked into what I'd do if the 454s gave it up. Its been awhile though. As I remember, the 496 HO motors would be wasted on a B31. The extra HP was up top--at 3,000 rpms the hp and torque numbers were almost the same as the regular 496. If you're going carb, I'd stick to the basic 454s. They pushed the boat fine. Do you have 454s now that you can use as a base? If so, I'd ask around for the best shop in your area and get the long blocks rebuilt. I've found that good speed shops know what they're doing and if you're by the water, they know boat motors. If you don't have 454s now, look around for good RTOs and get them gone over (belts, hoses, accessories) before they go in your boat. How heavy is your B31? A guy by me has been running 350 small blocks in his B31 for years, and his cruise numbers were close to mine with 454s, except he burned less fuel. He also had a lot more room under his engine boxes. My B31 had 1.5/1 gears and they were fine. What size shafts do you have? Would 2/1 gears require you to go up in shaft size? Good luck on the repower and keep us posted. 454s will run for a long, long time with minimal care. Great motors.

I had 454's in my 31 for 15 Season's. They were opposite rotating Mercs with velvet drives. I think they were 340hp. They had around 2500 hours on them when I soId the boat.

When I first bought the boat, she was fairly light, and would get up above 37kts at WOT. As I added fuel, hard top, A/C, etc...
over a few years, WOT dropped back to about 34kts.

In NJ, range is a huge constraint, so even with nearly 290 gallons, I'd run her around 2350 at 21 or 22 kts.

The bottom line for me was that the 340hp 454's had all the power she'd ever need, but you could only use it on demand. This is because the fuel consumption would go through the roof when the secondaries kicked in and you were trying to cruise above 25kts.

So for a fishing boat, I would think Hi-Po ~454 engines really don't add much benefit in the 31.

Mike

Thanks for the input guys...I got a set of excellent running 454 Crusaders for almost nothing...My current plan is to install all the 1 1/2 inch running gear that I got when planning on the original diesel conversion plan...I figure I will install everything that will be needed if anyone decided to go to diesel later on...I expect my boat to be somewhat light, and 25-26 kts would be more than fine for me...So what I am trying to decide on is should I go to a 2/1 transmission and swing a 20 inch wheel(1.5 Velvets came with the engines), and I am going to see what the price points are to add High Output Heads and Cams and try to bring HP up to the 400 range and torque around 500 f/lbs in the 3000-3200 range...What I do not know is what the secondary action and resulting fuel performance will be if I convert...The other part of me is KISS...and just go over the engines, belts hoses, pumps etc. and go from there...The dollars will decide as I won't drop 10,000 on the conversion....Any additional thoughts on gear choice and resulting fuel burn/performance at 3000-32-3400 would be appreciated...

MikeD@Lightningshack wrote: I'd run her around 2350 at 21 or 22 kts.

Does running the 454s at less than 3000 rpm put additional stress on them (assuming that the props are correct)?

Thanks,

My 340hp had 1.52 Velvet drives that seemed bullet proof to me. 1-3/8" shafts were more then adequate for my installation.

I have no experience with high-po engines in gas boats. I think most of us run our Bertrams more like buses, cruising for long distances at a set speed and RPM. Unless you can get a bunch more torque from a high power engine at a cruising RPM that you are comfortable running at, I think the HP approach might not pay dividends.

Mike

I ran them at lower RPMs, because in my configuration fuel economy seemed best in that range. As long as they are propped right to make rated RPM's you can surely cruise at 3,000RPM provided you have the fuel to get where you are going and back.

I think it might be more of a 2000 hour installation if you cruise at 3000rpm. I know folks that got close to 4,000 hours, and I'd bet they were crusing at lower RPM range and of course being really proactive on maintenance.

For me it was about fuel range, and longevity might have been a fringe benefit.


Mike

Properly propped 454's can all day under 3000 rpm. Actually on s gas engine that extends the life of the engine.

When we had the 454's before the repower at 3000 rpm's we were running at 19 knots. These were early model mercs with Rochester carbs.