Classic SeaCraft Community - Twin I/O's to Single I/O

Why change? If I were going to comment, I'd say change to a single diesel sterndrive for economy and longevity. A single Cummins Mercruiser 320 diesel will give the power, torque, and economy you need in this boat, and together with the Bravo Three drive system weighs only 1296 lbs.

For comparison, the 350 Magnum MPI with B3 drive weighs in at 980 lbs not counting the outdrive, and the 6.2L 320 MPI small-block weighs 860 lbs plus the drive. ( I don't know why the Cummins site gives you total power system weight, and Mercury Marine only gives you the engine & transmission weight for these two engines) The big-block 496 MPI 375 hp Mercruiser complete system with B3 drive is 1224 lbs.

Or, you can go with twin 150 2 litre Merc turbo-diesel sterndrives and only increase the total engines & drives weight to 1564 lbs.

Make those twins gas 135's 3.0L with Alphas and your total drive system weight for both is 1270 lbs.

If you prefer Volvo, they have a small 130 hp turbodiesel sterndrive system that weighs 716 lbs, as well as the duoprop equipped 280 hp diesel at 1441 lbs. The 350 hp VP duoprop sterndrive is 1693 lbs, or as much as twin 350 hp Suzuki outboards.

BMW used to make a diesel sterndrive system for sale in Europe and Asia, but I don't know if they still do. They used Volvo Penta drives with the BMW naturally aspirated engines of 120 or 220 hp. SeaLink in Australia still has sparse info on their site about these for those who are repowering AWAY from BMW systems.

Finally, there is the Yanmar family of diesel sterndrives, which are the lightest weight of them all. A single Yanmar 6LPA-STZP 315 hp system is 526 kilos with a Bravo Two X drive. That's less than 1200 lbs. The 150 or 180 hp 1.9L Yanmar sterndrive engine & transmission package is only 251 kilos, not including the drive and gimbal. That's 30 lbs less than the 135 hp gas Mercruisers.

The upfront difference, of course is cost.