2850 lower unit conversion-gctid394803

[Guest]

Well it broke this weekend 24 miles from the slip. The rat is a '98 build 2850 that we just love but with a 250 HP mercruiser and Alpha 1 drive it is extremely under powered. Bought the boat about 2 yrs ago and it's lack of power is really the only issue. Since the alpha drive is out I'm wondering what mods would have to be made to repower this boat with a 383 (no larger due to generator/space issues) and a Bravo III? I'm going to be checking with several shops during the next week. Anyone ever tried to do this upgrade to a 2850?

[Guest]

redriverrat wrote:
Well it broke this weekend 24 miles from the slip. The rat is a '98 build 2850 that we just love but with a 250 HP mercruiser and Alpha 1 drive it is extremely under powered. Bought the boat about 2 yrs ago and it's lack of power is really the only issue. Since the alpha drive is out I'm wondering what mods would have to be made to repower this boat with a 383 (no larger due to generator/space issues) and a Bravo III? I'm going to be checking with several shops during the next week. Anyone ever tried to do this upgrade to a 2850?

It's quite straightforward... toss the engine and drive and put a new engine/drive in. Same transom cutout/engine mounting position/etc.

Get out your check book!

[2850Bounty]

Several members have done this, but I'm not sure how many were in the 2855.

I'd not recommend doing this in front of an A drive that is apparently close to it's limit @ 300 hp and/or a 26 ft boat.

If you're going to build a 377/383 SBC, search the forum to see the different methods for building this engine.

[Guest]

I'm looking for a shop in the North Texas/DFW area that has the facility and experience to tackle this job. Any help or direction would be greatly appreciated. I'm really considering doing this but I need to talk to someone that knows this make of boat and what my real world options are. Thanks for any help in advance.

[Guest]

2850Bounty wrote:
Several members have done this, but I'm not sure how many were in the 2855.

I'd not recommend doing this in front of an A drive that is apparently close to it's limit @ 300 hp and/or a 26 ft boat.

If you're going to build a 377/383 SBC, search the forum to see the different methods for building this engine.

repower this boat with a 383 (no larger due to generator/space issues) and a Bravo III?

I think he was already covering the overworked Alpha issue, Rick.

[2850Bounty]

Jon, you are correct! I guess that I was reiterating the point.

Unless this hull has the potential for 45+ mph, I'd do a Q/E build 383 and use the V/P Duo Prop drive.

If it does have a 45+ mph potential, then I'd do the BIII drive.

I believe it was Don S who posted comparison test results many years ago.

.

[Guest]

2850Bounty wrote:
Unless this hull has the potential for 45+ mph, I'd do a Q/E build 383 and use the V/P Duo Prop drive.

If it does have a 45+ mph potential, then I'd do the BIII drive.

V/P might be a viable option as well. I know when I bought this boat every 2855 I looked and and read about had a Bravo III. In respect to the hull, is there any issue putting one of these other outdrives on a hull that previously had and Alpha drive? Power options run in the 320 to 325 range and I really don't think that will every allow this boat to do much over 30 MPH on a good day. I think I'd have to drop it out of a C130 to get it to 45 MPH.

[2850Bounty]

The test results do show that the V/P Duo Prop drive performs better at/near the 45 mph mark and under, and that the Merc BIII performs better at above this mark.

I don't know the charateristics of your hull, but I'm going to suggest that it is a below 45 mph boat.

In which case the V/P Duo Prop would be a better choice, IMO.

If you were to do a DP-S style drive, the same transom cut-out is used.

However, if you were to do a DP-C or C1 style drive (a much better choice, IMO) the transom opening will be increased.

DP-S style drive = gimbal system suspension, thru-hub exhaust, rubber hub engine drive coupler, annual engine coupler alignment, more timely bellows replacement, etc, etc.

DP-C or C1 drive = main suspension fork/pivot tube geometry, no thru-hub exhaust, no rubber hub engine drive coupler and no annual coupler alignment, easy bellows replacement, etc, etc.

FYI and FWIW:

Both the DP-S gimbal system drives, and the DP-C main suspension fork/pivot tube geometry drives, were produced side-by-side up through the mid 90's.

Bayliner boats never saw either of these drives.

Point being: if switching to a Volvo Penta DP-C style drive concerns you with regard to a conflict with your year model boat, it does so only with Bayliner boats.

Many boat brands of the mid 90's vintage can be found with either the SX or DP-S style (Gimbal system), or the SP-C or DP-C style drives (non-Gimbal system).

The decision for me would be an easy one........... DP-C, DP-C1 or DP-C2.

No rubber hub drive coupler to fail, no annual engine alignment EVER, no Gimbal system, no thru-hub exhaust, and very user friendly drive shaft bellows replacement!

The equivalent of a Gimbal bearing now becomes a PDS bearing that is completely serviceable from AFT. No need to remove an engine for bearing replacement as with the earlier V/P drives.

I must admit that before I became a Volvo Penta enthusiast, the Auqamatic White and the old look was a turn-off to me. They were not pretty like the Merc's, nor did I see as many of them. Then I familiarized myself with them!

There are both strong and weak points to either drive.

Attached files [img]/media/kunena/attachments/vb/699989=29322-DP C drive.jpg[/img]