Re-powering Bertram 42

Andrew 72 · Jan 12, 2014

Hi to all, i would be most grateful for your advice.
this boat has twin 430hp,which are dead. i,m trying to redesign the engine size to my particular needs. all i want do is 8 to 12knots for trolling and be fuel efficient at that speed. would this be possible with this hull as its a semi displacement not displacement, i need know this achievable first. this boat is 20 tons and come on the plan at 14knots with the 430,s. but i dont need that it to plan, is this possible to re -power with say 220 hp engines?

ranger58sb · Jan 12, 2014

Might help folks answer if you say which model Bertram.

I'd have thought that would more likely be a planing hull, not even semi-displacement. Just a guess, though...

-Chris

RickB · Jan 12, 2014

He did. Vessel name, vessel model ... you might be familiar with it.

sunchaser · Jan 12, 2014

Andrew, two questions, assuming vessel is in UK:

What brand and model are the current engines?
If you repower are the current Euro regs restrictive as to emissions?

On boatdiesel.com there are several UK members that could offer some help also.

RT Firefly · Jan 12, 2014

Greetings,
Welcome aboard. Something tells me even 220 HP engines would be to much. I vaguely recall some sort of "ideal" for what a vessel needs to achieve certain speeds. Something like 3HP per ton or 20 HP per gallon of fuel????? Can't remember at all but I'm sure some of the younger folk can enlighten you.

sunchaser · Jan 12, 2014

RT Firefly said:
Greetings,
Welcome aboard. Something tells me even 220 HP engines would be to much. I vaguely recall some sort of "ideal" for what a vessel needs to achieve certain speeds. Something like 3HP per ton or 20 HP per gallon of fuel????? Can't remember at all but I'm sure some of the younger folk can enlighten you.

RTF - my guess is the 220 HP was suggested by Andrew because it matches the ubiquitous Cummins 6 cylinder reman that is cheap, simple, reliable and available. Just a guess though.

O C Diver · Jan 12, 2014

Andrew, the first thing you will need to do is determine if 20 tons is an actual weight or is the size area of the boat. Boats of this size in the USA are often listed in tons which is area and pounds which is displacement, not sure about the UK. My gut feeling is that 40,000 pounds for a 42' planning hull seams high.

While I think the Cummins 6BT 220s would work, one needs to understand that planning hulls are fuel efficient in displacement (7 to 8 knotts for a 42'), and somewhat efficient on plane (say 14 knotts for this boat), they may be really inefficient between 9 and 13 knotts. Basically most planning hulls start to push a big bow wave when they exceed hull speed and before they attain planning speed. Takes a lot of energy (fuel) to make a big bow wave.

Ted

HopCar · Jan 12, 2014

My first thought was that you'd ruin the resale value of the boat. My guess is that there are very few people who would want a Bertram that underpowered. Bertram's are built to go fast in rough water. If you were in the US I'd tell you to consider selling the Bertram and get a boat like OC Diver or mine which are designed to travel the in the speed range you're interested in.

RT Firefly · Jan 12, 2014

Greetings,
Mr. H. I would think a re-power of any vessel to a performance level not similar to original would impact on resale for sure BUT if the OP already has the vessel and is not terribly concerned about resale, the engine choices are pretty well limitless.
One could even go so far as to suggest running one engine and driving the two props. I think there are transmissions/drive trains that would allow this.
My initial comment was directed to what is the minimum HP necessary to achieve the desired results (12 knots max.) and I still think twin 220 HP is too much.

rochepoint · Jan 12, 2014

RT Firefly said:
One could even go so far as to suggest running one engine and driving the two props. I think there are transmissions/drive trains that would allow this.

The boat across the dock from us did exactly that..........

sunchaser · Jan 12, 2014

rochepoint said:
The boat across the dock from us did exactly that..........

Is that called the Geared Up system. Philbrooks has been pushing this for a few years. BTW, nice clean install, but where is the exhaust run, RW feed line, fuel lines etc?

Richard W · Jan 12, 2014

O C Diver said:
While I think the Cummins 6BT 220s would work, one needs to understand that planning hulls are fuel efficient in displacement (7 to 8 knotts for a 42'), and somewhat efficient on plane (say 14 knotts for this boat), they may be really inefficient between 9 and 13 knotts. Basically most planning hulls start to push a big bow wave when they exceed hull speed and before they attain planning speed. Takes a lot of energy (fuel) to make a big bow wave.

Just to expand on this ... using the standard 1.34 factor, the displacement hull speed for 42' boat with LWL of 40' (just a guess) is approx. 9.5 knots. Anything more and the hull is being pushed up and over own bow wake and wastes a lot of fuel until it goes on plane (if capable).

Plan for that boat to cruise efficiently up to 9.0-9.5 knots.

sunchaser · Jan 12, 2014

Richard W said:
Just to expand on this ... using the standard 1.34 factor, the displacement hull speed for 42' boat with LWL of 40' (just a guess) is approx. 9.5 knots.

I get 8.5 knots @1.34 and using a more efficient 1.2 multiplier about 7.5 knots.

Andrew 72 · Jan 12, 2014

thanks for all the reply's,
the boat is 1986 Bertram 42c sport fisher.
info i have is 20 ton actual weight and 39,400 lbs displacement.
existing engines are detroits 6v92 tas @430hp,
re powering with big like this size is,nt an option due cost.not worried about resale just cheap reliable running cost at that trolling speed.and enough power in a rough sea!
want it to take Madeira and set up a big game fishing charter.
i know this boat was designed for high speeds cruising at 18 knot and top 30 knots.

My concern is because the hull starts deep v then goes th shallow, with a planning chins that goes down it length,with low power would be fighting to push the vessel up ! and have a strange effect on performance. if it full displacement it would be easier to work out.

Andrew 72 · Jan 12, 2014

Ted, hit the nail on the head with my concerns

rochepoint · Jan 12, 2014

sunchaser said:
Is that called the Geared Up system. Philbrooks has been pushing this for a few years. BTW, nice clean install, but where is the exhaust run, RW feed line, fuel lines etc?

Yes it is the Geared Up System, the photos are just of the base mechanical installation done at Philbrooks.

Richard W · Jan 12, 2014

Andrew 72 said:
My concern is because the hull starts deep v then goes th shallow, with a planning chins that goes down it length,with low power would be fighting to push the vessel up ! and have a strange effect on performance. if it full displacement it would be easier to work out.

My pocket express cruiser with modified-V planing hull and LWL of around 25' cruises efficiently up to 7 knots (exactly as the formula says).

The hull does not track well in the displacement mode as it is a modified-V hull ... or ... a modified flat bottom hull ... pick your poison ... :blush:

Xsbank · Jan 12, 2014

I thought the idea behind a sport fisherman was to go like hell to the fish, spend the time fishing, not travelling, catch some fish and then zoom back to the marina to display the corpses? Isn't travelling at trawler speed a contradiction for a fishing charter?

capt jerry · Jan 12, 2014

Andrew 72 said:
thanks for all the reply's,
the boat is 1986 Bertram 42c sport fisher.
info i have is 20 ton actual weight and 39,400 lbs displacement.
existing engines are detroits 6v92 tas @430hp,
re powering with big like this size is,nt an option due cost.not worried about resale just cheap reliable running cost at that trolling speed.and enough power in a rough sea!
want it to take Madeira and set up a big game fishing charter.
i know this boat was designed for high speeds cruising at 18 knot and top 30 knots.

My concern is because the hull starts deep v then goes th shallow, with a planning chins that goes down it length,with low power would be fighting to push the vessel up ! and have a strange effect on performance. if it full displacement it would be easier to work out.

not many people who charter a boat don't want a slow one they want to get there to fish,not spend all day getting ther

RickB · Jan 12, 2014

The OP wrote: " i,m trying to redesign the engine size to my particular needs. all i want do is 8 to 12knots for trolling and be fuel efficient at that speed."

That is the bottom line and if anyone can help him obtain that objective I am sure he will be happy and glad TF could help. I can't find any request for opinions on if the idea is "good" or not.

A string of folks telling him what he wants is not what they want or would do is no help to anyone.

Andrew 72 · Jan 12, 2014

well it probably depends on how far your fishing grounds are! in Madeira Portugal you start trolling as soon as you leave port. the bertram is a great fishing platform at trolling speed in a lumpy sea ,so why not. most big game fisherman are catch and release there big fish now and thats how it should be !

N4712 · Jan 12, 2014

Andrew 72 said:
well it probably depends on how far your fishing grounds are! in Madeira Portugal you start trolling as soon as you leave port. the bertram is a great fishing platform at trolling speed in a lumpy sea ,so why not. most big game fisherman are catch and release there big fish now and thats how it should be !

ranger58sb · Jan 13, 2014

RickB said:
He did. Vessel name, vessel model ... you might be familiar with it.

Ah! Sorry, you're right.

I saw the 42, but on my screen, the "c" is wrapped way to the left on the next line, and I didn't see it.

You'd have thought I might have noticed that!

Definitely a planing hull. (I notice the spell-checkers always think that should be "planning.")

-Chris

ranger58sb · Jan 13, 2014

Andrew 72 said:
thanks for all the reply's,
the boat is 1986 Bertram 42c sport fisher.
info i have is 20 ton actual weight and 39,400 lbs displacement.
existing engines are detroits 6v92 tas @430hp,
re powering with big like this size is,nt an option due cost.not worried about resale just cheap reliable running cost at that trolling speed.and enough power in a rough sea!
want it to take Madeira and set up a big game fishing charter.
i know this boat was designed for high speeds cruising at 18 knot and top 30 knots.

My concern is because the hull starts deep v then goes th shallow, with a planning chins that goes down it length,with low power would be fighting to push the vessel up ! and have a strange effect on performance. if it full displacement it would be easier to work out.

Andrew, maybe some useful data I can supply.

Our boat -- similar to yours, although lighter: planing hull, 35 gross tons (volume), and about 28,500-lbs displacement -- was manufactured with Cummins 370Bs, 450Cs, and Volvo 480s. Maybe some Yanmar 480s; not sure. Might actually have been a very (very) few with gas engines, no further info on that.

I spoke with an owner who had 370Bs and he was guite satisfied with performance. I didn't ride on that boat, but he sounded like he had a clue. He described cruising speeds lower than ours, I think in the 18-19 kt range. I don't remember what he said about tops speeds. (Our cruise with 450Cs is usually somewhere between 19-21 kts; we usually run at around 7 kts, though.

)

Don't know what a 370B, perhaps reman, might cost, but I understand they're readily available.

Not a recommendation, just an observation.

-Chris

Moonstruck · Jan 13, 2014

Will we be seeing the first Bertram with paravanes?

cafesport · Jan 13, 2014

Andrew 72 said:
Hi to all, i would be most grateful for your advice. this boat has twin 430hp,which are dead. i,m trying to redesign the engine size to my particular needs. all i want do is 8 to 12knots for trolling and be fuel efficient at that speed. would this be possible with this hull as its a semi displacement not displacement, i need know this achievable first. this boat is 20 tons and come on the plan at 14knots with the 430,s. but i dont need that it to plan, is this possible to re -power with say 220 hp engines?

One of things you might want to consider is that your 692's though heavy contribute considerably to the ballast and seakindliness of your boat. I have a 38 blackfin convertible, probably 10" less on beam and 10" more on draft than your hull. Fully loaded fuel water ice etc we are looking at 26 tons. We have the same engines but mine are j&t modified to 550hp and I have no tower. When trolling in big seas, the boat can be brutal at times. Not as bad if your amidships on the cockpit deck which is about 6" off the water but driving from the flybridge be prepared to brace yourself. At 12 knots it's manageable and on plane a whole different story, but I can't get her there on one engine. Two 250's maybe, if they were much lighter, but then I'd loose my ballast. The new berties have gone to much less vee and are now using gyro stabilizers for slow speed work.

In 1985 I was anchored in Funchal, waiting out a force 8 blow that seemed to come up out of nowhere. Nothing to do but windsurf all day in the rollers entering the harbor mouth. Definitely wouldn't want to be trolling at displacement speeds in those conditions. Most of the commercial fishing boats I saw were old school wooden portugeuse dories. Yes and there were a couple of Bertrams. Could have been your boat. Anyway the reason these boats go long on power is for the sport of bill fishing. Power is not always about speed, it's often about having agility when backing down in rough seas. My cockpit is 12x10x2.5 feet and I remember very well the first time it started to fill with water. Glad to carry 1100 ponies just for those occasions.

Via iPad using Trawler

twistedtree · Jan 13, 2014

Go register at boatdiesel.com and pay the membership fee. Then use their calculator to experiment with different engine sizes and see how fast each will make the boat go. What you get out of boatdiesel will repay the membership cost over and over again.

Andrew 72 · Jan 13, 2014

thank you for a great reply, there,s alot to think about and alot i did,nt consider.

Marlinmike · Jan 13, 2014

You should be able to just run your boat now and take down the RPM and the speed, do this from 5 knots up to 10 knots. The RPM/HP curve for that engine (do a search for chart), those HP numbers will show you what you need at the minimium.
I think the Cummins 220hp reman'ed would fit the bill nicely, put in a nice gear and a tall ratio like 2.5: 1.

FF · Jan 14, 2014

His big problem is that 8-12K desirement.

At 8K the boat could cruise on very modest engines , although 7K would be markedly cheaper.

The hassle is it will require at least double the installed power for 12K , although with the surface area of the deep V it could be closer to triple.

The ride advantage in heavy water of the deep V is lost as a displacement boat , so only the extra drag is left.

SHOCK SHOCK !!! This boat might be better with a set of gasoline engines , as minor power does no long term harm and the need for big HP could be met as required.

Impractical as the entire engine room electricals would need replacing , and Im told gas is not dockside often in europe.

The easiest compromise might be a high out put diesel car engine.Yanmar or similar.

Small size so 30-40 HP each at slow cruise might not cost a fortune , and getting up on the plane would still be possible, for very limited time.

Lowest cost of all might simply be to overhaul , inframe the existing engines and set them up for a lower top HP output , just timing and injectors during the overhaul.

Resale would be maintained and saving $50K per engine package could pay for lots of diesel.

Re-powering Bertram 42

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