D4s in a 25?

davidms · Post by **davidms** » Oct 6th, '07, 19:46

I posed this question to the guys on the Bertram 25 website.

I am considering putting twin Volvo diesels in my inboard 25. Here are the choices:

D4 (180 hp) 2800 RPM rating 4 cylinder

D3 (190 hp) 4000 RPM rating 5 cylinder

I was told by one of the guys on the 25 webste that Bruce has repowered a 25 with D4s. Bruce, could you give me some more information on how that repower worked?

Scot, you have posted in the past that you thought anything more than 350 total HP is too much. Should I consider smaller D3s?

What do you all think about higher vs. lower HP, higher vs lower RPM rating and the diffence between 4 and 5 cylinder in terms of noise and vibration?

Davidms

Ironman · Post by **Ironman** » Oct 6th, '07, 20:04

Check this guys project... Cummins single. 330 hp. Id move the helm forward.
(Ever drive a 25 from lower station?? )
http://www.cssims.com/JG6B.htm

ianupton · Post by **ianupton** » Oct 6th, '07, 20:09

David,

Sorry 'bout that typo... it was a B31. "Time Machine" I think.

Ian.

scot · Post by **scot** » Oct 6th, '07, 20:44

I believe that anything over 350hp (diesel) is basically wasted in a 25B. The hulls just don't require a lot of power to work well and the design speed of the hull is not very high, maybe mid-30's? Jim's 6BTA 315hp, 1.5:1 gear and 20x23 wheel is one strong machine. I basically know nothing about Volvos.

My comments would be directed to inboard configured boats. Are you considering re-powering a 25 V-drive inboard?

I'm the wrong guy to discuss I/O's with because I really don't know very much about them. As a rule they don't do well when left in the water and require much more attention than inboards. They are faster but not one of my favorite drive drains by any stretch. I like boats that can be left in the water and are simple....like me.

davidms · Post by **davidms** » Oct 6th, '07, 22:30

Scot,

I have an inboard and V-Drives. Sounds like you think the D3 190Hp are overkill. I think the next step down in 170 HP. What do you think about 2 170s?

Rocket · Post by **Rocket** » Oct 7th, '07, 01:35

Scot, I think the 25's are happier at higher speeds than that. I propped my 25 with twin 318's so she would make 40 knots at WOT and found that she actually felt very stable and handled better at that speed than in the mid 20's. You know I like to go fast, though so take it with a grain of salt.

scot · Post by **scot** » Oct 7th, '07, 08:55

David...D4. I like slower turning diesels (I'm old school) and it should be an easier fit? Give it a try, we all want to see how it comes out. There is a lot of discussions about re-powering the twin V-drive boats with diesel.

Rocket,

I'm not saying they won't go there...I'm saying they don't need vast sums of HP to perform well. "REAL" speed is a different story and YOU are the man to talk to about that!.....geez, a 62mph Baron!

J Graham · Post by **J Graham** » Oct 7th, '07, 16:37

Ironman, right you are, the console will be modified this winter with the helm at the forward end of the engine box and elevated steering. Visibility is limited at current position.
IMO, there is no substitute for HP. Two of those 190 D-3 would be a rocketship. Love to see that in a v-drive 25.

Ironman · Post by **Ironman** » Oct 7th, '07, 17:43

Seems to me that would be a perfect boat for a small tower..
Wayne

ianupton · Post by **ianupton** » Oct 8th, '07, 10:12

I was out in a Bertram 25 Hardtop repowered with a single 496 HO and Bravo III.

It was only me and my 3 and 5 yr old. 52 mph on the GPS. I probably could have played with the trim and such to get a few more, but the boat wasn't mine, etc.

Ian.

In Memory of Vicroy · Post by **In Memory of Vicroy** » Oct 8th, '07, 15:54

In 1984 I pulled the orginal 165 Mercruisers out of my B25 and installed a pair of Vulva AQAD31 diesels with the Duoprop outdrives. Made her stern heavy and got about a 21 kt cruise, but only burned 8 GPH at that speed. Doel-Fins and big trim tabs helped get her level at speed. The engines were 110 hp 4 cyl. turbo & aftercooled. Engines drove me nuts with the 4 cyl. 4 stroke "rattle" and parts constantly fell off the motors. Plus a very tight fit made maintaince a headache. Parts were stick-em-up expensive and the whole deal cost me in excess of 20K back then. On the other hand, Da Judge put gas Mercuriser 4 cyl. 135s with Bravo Ones in his B25 for short money and it runs better than my diesel one ever did. On a 110 n.m. trip from my camp to Venice running together, my B31 with Cummins 250s burns 83 gallons and he burns 55, both of us running 24 kts, and we have done the trip 3 or 4 times together.

Too much motor money for the boat.

UV

randall · Post by **randall** » Oct 8th, '07, 16:25

i think the new volvos are a lot better suited and its been done with great success.....but my 1984 chryslers some how just keep chugging along so ill wait till the new super small high effiecent and inexpensive diesels come a long...........long wait...huh?

bertram31.com

D4s in a 25?

D4s in a 25?

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