Bertram 25, 350hp diesel

Bruce · Post by **Bruce** » Oct 9th, '06, 18:51

Had someone enter the shop today who is putting a Yanmar 6LY/350 inboard in his 25 Bertram.

I was very polite to him today and said I would help him at various times when he needed it during his project.

After thinking about this all day and in hopes that he may see this post" are you nucking futs?"

In Memory of Vicroy · Post by **In Memory of Vicroy** » Oct 9th, '06, 19:11

Now, now, Capt. Happy Pants..... The original twin 165s totaled 330. Stan Smith (the Port Eads Helldiver - "you mean there is a season and limit on spiny lobsters?") had a buddy that put a single Vulva 62 (think it was 300+ hp) in a B25 and they raped the Gulf in it. I put the Vulva diesel 110 hp 4 bangers in my B25 in 1984 and it was slow, say 21 kts, but sipped diesel back when diesel was two bits a gallon. 350 in a B25 is plenty, but not too much. Dem suckers are way heavy.

Is the guy gonna do i/o or straight?

UV

scot · Post by **scot** » Oct 9th, '06, 20:08

I'm in the beginning stages of a B25 re-power. The 350 HP is really not the question, it's the weight and the Yanmar is fine. The secound major issue with a 25 is engine placement....these hulls need the weight as far aft as possible. CB is 10ft forward of the stern (Per Ray Hunt) The factory sold hundreds of these boats with twin V8 Vdrives and the combined power plant weight was pushing 2400 lbs worth of engines and drives.

The B25 hull is not that far off the 31. From a proportional standpoint the 25 is actually a little wider at 10ft. Having spent the last few months measuring and surveying my 25 hull and doing the math, the boat could handle a single 3208TA from a space and weight standpoint. The only problem is finding enough room for fuel! From a size and weight perspective a 31 with twin 330HP 6BTA's is carring much more weight and power than a single 350HP B25. And you know there are 31's with V8 Cummins at 2,000lbs+ each!

A lot of B25 owners are going the big block gas route with 40+ kt results and those guys couldn't be happier. I realize 350 HP gas is not the same as 350 HP diesel as relates to pushing boats. My boat will more than likely get a 4BTA 250HP but that's more about fuel capacity, consumption and range than it is about the boats ability to handle it.

Help him out if you can, your extensive knowledge will be a great resource for him. I think you'll be surprized at how well the 25 handle the HP's if it's set up correctly.
Scot

nic · Post by **nic** » Oct 9th, '06, 20:24

Does anybody run this all by Raymond Hunt Assoc.? I'm surpised they don't participate in the forum, did they ever?

Nic

scot · Post by **scot** » Oct 9th, '06, 20:49

I corresponded with them and they were very helpful....provided the basic CB / CG info on the 25 at no charge. I have another buddy from the Bertram25 board and they also assisted him. The will tell you facts about the hull but they will NOT make specific recommendations. I guess if you put them on the pay roll they would provide more. The main thing they did emphasize was keeping the weight at far aft as posible on a B25. The problem with mid-ship engines on the 25 is not the engine weight in the middle of the vessel....it's the massive amount of bouyancy in the stern. Mine will be straight shaft but will require a pocket and EVERTHING heavy placed aft to move the CB & CG.

John Jackson · Post by **John Jackson** » Oct 9th, '06, 21:48

I have a friend who put a big four stroke outboard on a B25 on a bracket and made it into a sweet custom center console. Nice boat, the Sportscaster docked at Robinson's in Manasquan. You really have to look to recognize it as a B25.

scot · Post by **scot** » Oct 9th, '06, 21:55

The B25 outboard conversion is really popular now, the purist make nasty faces but the boats seem to work really well with the advent of 250hp bolt-ons.

SteveM · Post by **SteveM** » Oct 9th, '06, 22:19

I too have a friend that converted a B25 to outboard. Very nice job. Scot's remarks about putting weight aft is true. The outboard conversion guy had to keep putting concrete in the stern till it set just right.

randall · Post by **randall** » Oct 10th, '06, 08:38

huh? my 25 has twin 360 chryslers (1984 vintage)....about 215...225 hp each............honest 40 knot boat......10.5 GPH at anything that keeps the secondarys closed (3300rpm) and the scuppers are well above water...which is nice......where i am confused is.... take last week....6 large friends on board......the more weight forward (to a point) the faster on plane the easier the run ....the more weight aft....the harder on plane and more energy needed to stay there.....also Bertram made less than 200 inboard v-drive 25"s .....almost all i think with 318's

ianupton · Post by **ianupton** » Oct 10th, '06, 11:20

I think the weight in the B25 needs to be abit further forward... The sterndrive 25's run bow high.

I have never been on an inboard version, but I hear they ride abit more 'solid' with a couple of V8s forward.

I think concrete was needed with the outboard conversion because of the added flotation of the bracket.

I personally think a mid engine set-up like the Surfhunter and Harriers would be the way to go on a B25.

Ian.

randall · Post by **randall** » Oct 10th, '06, 11:34

ian....for three years i sea trialed every B25 for sale on long island.....when i finally got a ride on an inboard it was night and day.....3-4 foot cross chop in a large closed bay.......i knew i was going to buy the boat after five minutes....it just feels way different.......

scot · Post by **scot** » Oct 10th, '06, 12:37

The twin Vdrives do move the weight more forward than the IO's. Randle if you'll notice your cockpit scuppers, or drains are about 3"-4" higher than the IO boats...hence a higher cockpit sole setting.

When I purchsed my boat it was originally an IO...there were two drain plugs looped around eack cleat in the stern, one on eack side. The boat originally had the Merc 470s and I think those plugs were for the deck drains to keep the water out of the boat!

I hope you guys are right about the ride with the weight a little forward because that's exactly where I'm going to put it. The nose of my engine will be around the 9' mark from the transom....we'll see!

Rocket · Post by **Rocket** » Oct 10th, '06, 13:15

Randall is definately right weight forward and low is a very good thing on these boats, if I was doing a diesel/sterndrive repower I would centre mount the diesel and run a jackshaft to the sterndive. I think a friend of mine is going that route in repowering my old 25 FBSF that has two tired (very) 318's in it. I'l report back when and if it gets done.

Bruce · Post by **Bruce** » Oct 10th, '06, 16:52

Yes the vdrive v8's run great but I'm talking about a single straight inboard with 2:1 gear with the nose mounted somewhere near the cabin door to try and keep the angle down and clear the prop
.
To swing the prop needed on that 3300 rpm motor, the angle will be anything but practicle.

Now a proper way to do it would be a single diesel thru the twin drive mastry setup to bravo drives.

That is too much engine for a single drive. I serviced a boat that had a pair of 6LY/350's in front of bravo 3's.

I rebuilt those drives 3x a year for 3 years till they sunk the boat in 1500' of water.

scot · Post by **scot** » Oct 10th, '06, 17:30

The straight shaft B25 debate rages on lots of forums and everyone has various opinions. In an effort to put the straight shaft B25 questions to rest here is the conclusions that I have come to about this conversion to a B25:

1) It's a simple issue once everything is measured and CB/CG is varified and used as the guidelines.
2) The V is too deep to use "as is"...The existing V places the engine forward of the CB, not good and would create a 4' draft...bad for certain areas.
3) The hull needs a pocket or semi-tunnel added to correct the engine placement, shaft angle, etc.
4) The gear needs to be an 8 or 10 degree down angle version to facilitate the proper drive location...no 18" long Borg Warner reduction gears. Use one of the 8" long Twin Disc, ZF, etc.
5) I6's are not a great option based on length, I4's or V8's are a better choice.
6) All batteries, fuel, etc. should be located aft of the engine.
7) Take care to minimize weight forward of the CB.
8) Run a 1:1 to 1:5 gear, this keeps the required prop diameter to around 18" or less.

Bruce...what that guy is thinking about will not work. You may want to explain the location of the CB on his boat and how that relates to his plans. His I6 Yanmar would work ONLY if he takes these facts about the hull into account.

I did a straight shaft conversion on a 22 SeaRay which is a very similar Ray Hunt deep V. It's on my site: http://www.cssims.com listed under the Terri Lynn project. The boat is well balanced and works very well.

Lots of people will disagree with me on this but it's basic math based on weight distribution and hull's CB location.

Scot

nic · Post by **nic** » Oct 10th, '06, 18:04

Scot,

You've obviously done a lot more than most on this topic, so I hope my suggestion of another alternative is not a red-herring.

If ultimate fishability is not the priority then a single fixed surfacing propellor would resolve a lot of performance/weight issues. I have seen and driven simple fixed shaft installations, with the exhaust dumping onto the props to aerate it prior to planing, deliver great results, with much better performance and reliability than the widely known articulated surfacing props. Easy 20% improvement in speeds and fuel burn, ie from 32 to 38 knots in identical boats. You do need a bow thruster though.

The engineering is easy.

Nic[/u]

Bruce · Post by **Bruce** » Oct 10th, '06, 18:30

Bruce...what that guy is thinking about will not work

That was my original point.
I quit trying to talk people out of throwing away their money. After all I don't know jack.

Using a 1:1 or 1.5:1 on a low speed higher hp is useless because you can't swing a prop big enough to load that engine and take advantage of the hp.

A higher rpm diesel such as Steyr would be perfect in that application and ratio both in inboard and sterndrive.

RussP · Post by **RussP** » Oct 10th, '06, 20:56

I stoped by a comericial fishermans place a few years ago to check out his B25 single diesel inboard repower. He cut the lower v section of the hull and inverted it to create a pocket for the shaft. The glass work wasn't pretty but it worked. He dropped in a Cummins 4B and mostly fished near shore for cat food ( King fish).

RussP

Bruce · Post by **Bruce** » Oct 10th, '06, 21:56

That just proves if you put the right gene pools together, you can bastardize anything.

scot · Post by **scot** » Oct 11th, '06, 09:32

"Cat food" is correct!...I've tried a dozen ways to make those things fit-to-eat and I don't think Emerald could make a decent meal out of one. I give up...but I think the little Spanish Macs are even worst.

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Bertram 25, 350hp diesel

Bertram 25, 350hp diesel

Weight Aft or forward???

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