What high horsepower engines for a 31

[JimmyG]

Peter,
Any of the new computer diesels are costly which is why the reman mechanical program is still a good deal.
Frankly unless your living on the boat running it daily and keeping track of exact fuel usage to the drop a casual user will never realize the difference between the electronic and mechanical engines

The other alternative I have been seeing lately mostly on the Yanmar side since the 6lp and 4lh are gone is buying a whole boat just for the engines, yanking them and selling the hull for a repower project. I know a few who got decent deals doing it this way.

I repowered an Egg Harbor one time with a pair of Volvos I pulled out of a burnt to the deck SF.
Nasty smelly job, but the engines were low hours and nothing on them burned.

Just a note for everyone.

This type of thread has come up numerous times. I've seen 31's do over 40 knots(gas boat) so they can go fast to a point.

BUT, having repowered so many styles and size boats (leaving out go fast style boats for now) matching an engine, gear, prop combo to take advantage of the power curve and hp output of an engine in a boat is important.

Why put a 400hp pair of diesels in a 31 if even with prop pockets your available cruse is going to be in the mid to high 30 knot range. Why spend the money on that power if it can not be leveraged? It makes no sense when for less hp and money you can get good safe performance that you can use.

The notion that the engines are working less so they will last longer is nothing more than silly thinking. If you load the engine to factory rpm recommendations and loading, they will do just fine and give you good service.
Engines need proper loading to burn fuel at proper cylinder temps to keep from carboning up. Its just a fact.

Can't tell you how many rag sailors in the effort to save fuel and wear and tear on the engines choked up the exhaust with carbon like butter does to your arteries.

The largest engines in the 31 I ever agreed to do was a pair of 330 QSB's when they first came out.
The boat had prop pockets and with a stripped hull, no interior at all top end was 36 knots but even with the pockets idle speed was stupid fast.

If one wants to go fast in a 31, gas is the only way to go, diesels need too much prop loading even at 1.5:1.


There's always someone who wants to put a 429 cobra jet into a 70 Pinto. Its part of being in the testosterone family.
With enough money anything can be accomplished, (well really nothing gov't related) but remember having a wife with 76 DDD's is more like a freak show than a useful play toy.

Bruce, I did just that I found a pair of Yanmar 315's out of a sandy wreck (damage not water) and they were sold before I could get a deposit on them! I'm sitting on the money just waiting to pounce on a deal weather its Yanmar or Cummins!

[bob lico]

Stage two;
Our boat will be built for long turn ownership so we prepare our Yanmars for the next century.we remove the antiquated fuel canister and replace with universal spin on filter adapter both fuel and oil filters are available every ware .we have installed Algae x then to 900 raccors with valves on tank,before and after raccors.all fittings bronze all threaded fittings with coast gurard blue piping.harry barb builds our custom mounts and we install triple Yanmars 315hp in the hole.next buju I have you covered just give me a chance you are needed to finish custom teak console with custom gauges as well as covering boards and teak door on head.on that subject we learn what NOT to do with a head in V berth .we will make access panel on hinges directly in front of console in V berth for wiring access.remove floor and we fit a porcelain Jabsco angle cut base to coincide with 24 degree dead rise .there is a wall and door to seperate head from rest of V berth you actually step down into head with total privacy head is fresh water with holding tank in former engine compartment area.NO holding tank where you sleep!.to be continue.

[bob lico]

Stage three;
The gimbals have been install very carefully cutting hole in our new transom with template following the dead rise. I will tweak center probally with 5 blade raked. What we have here is a well through out unique set up to run straight as a arrow with port / starboard duo - prop that you may run with or without center or just center for trolling .here we are after installation. Yep! We have tabs on this boat weight in extreme aft. will make this the best rough water 31' Bertram ever created however I for one fish off back of boat with raise area it would fish like center console with triple outboards and bring fish to side of boat to pull in.

------- to be continue

[alex n]

Let's hear more Bob

[bob lico]

I stop posting because I did not think anyone was following!

[Carl]

We/I stopped following when you stopped Posting.


But I think I start to wonder why go thru all that work to have a reconfigured 31. For me, once we lose the open cockpit I lose interest. But still would like to hear project to the end.

[Tony Meola]

I thought you just took a break. While some thing I would not venture into, it is really interesting following what you would do. Plus you never know, I hit the lottery, mabye i would do it.

[matt ciarpella]

Always following you Bob. Good stuff for fun. My guess is if you had to chine walk it would be nice to have 24 deg dead rise @ transom or would you be better off with 0 deg? Ive seen crazy from a few JS's

[Jamie MacKenzie]

Whoever repowered my '62 Express Cruiser installed 330 hp Pleasurecrafts. They're some kind of a small block V-8 racing engine with four barrel carbs.

She will easily run 24.5 knots at 3000 rpm. I haven't pushed any faster than that. My head starts to ring like a cash register. I can visualize the gas pump numbers spinning to infinity.

[Bruce]

Pleasure Craft engines depending on age used Ford engines. Distributor in front would confirm, 351 CID.

Distributor behind carb, GM.

[bob lico]

we have to assemble some facts at this point of building this 50 knot bertram.# 1. around this marina we have a term when somebody states there opinion " i have a friend whom has a brother whom has a friend that had a mercruiser outdrive" this is a dude with a paper asshole another words nothing to back opinion or statement.i helped installed that center yanmar in the above photo of that boat above ,i test drove this boat therefore i state there is absolutely no chine walking and the boat goes straight as a arrow at 50 knots end of story on that subject.# 2 when bertram built the 31 there was nothing in the outdrive world that would hold even a 260hp mercruiser. bertram had a outdrive on the 20,25' and 26' but that was " iron duke" 4 cyl. power. the merc stern drive with speed master lower unit hold 1500 hp now. so lets not scumbag mercruiser outdrives.the bravo duo prop hold it straight. one more time; i was on a sport fishing catamaran that cruise at 75 mph with wot at 104mph in 4 to 6' waves. twin 480hp Yanmars with 3 speed transmissions . yes i have photo of sister ship if you need to see.with the triple engine at stern our planning altitude are unlimited. we can trim outdrives to any sea conditions far,far superior to hanging 350hp yamaha off the transom at 29,000 a piece and you need three (that is a fact). you need torque to get that 13,000 lbs boat moving and maintain 50 Knot cruise.outboards 350 would be a little less then 10% of gross hp at wot. about 100 gals a hour a little less to maintain 50 . ok with the triple stp 315 hp Yanmars i could maintain that 50 knot speed at some ware around 30gph. to 35gph.this Bahia Mar would be flush deck from in back of pilots seat to a raised area at transom like 36' yellowfin,35 everglades,34 jupiter,38 contender, etc.i will photo bottom design tomorrow .time out must have snowmobile attain 140mph in 600'. turbo kits are in.

[bob lico]

The beam of the boat in photo is slightly less with a more rounded keel at stern the Bertram would even be better in all sea conditions although slightly less wot speed which we don't care about.

[BCBertie]

the 31 Bertram is capable of around 85mph with perfect running attitude and far better recovery in larger waves then a go fast 8' beam boat.

I thought we were building an 85 mph boat?

Cheers!

John

[bob lico]

Hull is Capable!

[CaptPatrick]

giggle -- smirk... ;)

[Tony Meola]

giggle -- smirk... ;)

I hear a doubter.

[Brewster Minton]

85mph? If you dropped my 31 off a cliff it would not go that fast. Lots of rod holders and ice. That's what you need! Just to stir the pot!

[Buju]

Bob, I appreciate the offer to do a bunch of brightwork, but gotta draw the line.
Im not real comfortable with bolster seats, and teak… in the same boat, or even the same sentence now that I typed it.

Unless of course they're solid teak bolsters, with nice white vinyl fighting chair style cushions… then game on sir.

[bob lico]

Neither am I buju but we need a margin of safety for pilot and co- pilot seating. We are getting carried away with this post. We are Not building a offshore race boat from a 31 Bertram hull! To do so would be a waste of time and money . Go buy a cigarette or whatever . Easy job just to go 85 mph in 31 hull . Order mercruiser 800 SC install with jack shaft and racing speed master mercruiser out drive ----- bingo 85 mph.boat would serve only one purpose and you would be giving up 5 mph at top end due to that 11'6" beam versus 8' in a a race boat of that 24 degree dead rise cut down empty moppie style . We were building a practical muti use 50 knot 31' Bertram for fishing and pleasure that would outperform any existing inboard bertram especially rough water handling.

[Stephan]

I think with some modification this may solve the bolster/teak issue:

and also the impending rod holder crisis.
So with those significant roadblocks removed by all means please carry on.
Jeebus it's cold out....
S
/sarcasm>

[neil]

my old bahia mar did 80mph on its way from virginia to new jersey but it was being towed by a semi,anything is possible

[bob lico]

Neil your talented son drove my boat at 34 knt. with 8 people on board .Ask him if it was even in the slightest bit squirrely .

[Kevin]

We need to pose this question to the Myth Busters and do it on their dime. I think they ran out of stuff to blow up anyways.

[Tommy]

What Kevin said! :-)

[Carl]

We need to pose this question to the Myth Busters and do it on their dime. I think they ran out of stuff to blow up anyways.

There is AlwayS more stuff to blow Up ;-)

[Tommy]

I want to add that I am thoroughly enjoying the thread and appreciate Bob posting all the technical info and photos; owners sharing different insights is what keeps this site going. The fact that Bob's 31 performs so well is a testament to his technical knowledge and abilities!

[Keith Poe]

http://www.dieselpowermag.com/tech/chev ... el_engine/" onclick="window.open(this.href);return false;

[Carl]

http://www.dieselpowermag.com/tech/chev ... el_engine/

Those scare me...I am thinking they are a time bomb installation. Government can afford to replace or rebuild after a few missions...not sure about the average Joe.

A Big Crank Pulley is an understatement.


I'd rather put a pair of correctly built blown 350 gas motors, run a couple seasons, rebuild and replace as needed.