Hi guys/gals, I need some help/info on numbers (efficiency) for a re-power my buddy is considering; here's some of the boat particulars.
1. California Radon-type hull @ 25'; beam about 8'
2. Boat currently weighs about 10,000 lbs. with single Cummins 210 diesel & Stern Powr outdrive.
He's considering a single diesel re-power (300 hp range Yanmar) with a V-drive or straight shaft, however this will mean considerable demolition & fiberglass work. Going with a v-drive or straight shaft means moving the motor forward into the fishbox area (not acceptable) so if going that route, lengthening the boat by 4' would be required.
In case you're wondering, the current Cummins is old and the hp is just not enough to push this boat past 18 knots and the Stern Power drives constantly break down (he's got 4 spare outdrives, all broken and a brand new drive costs 18k). We talked today about the re-power issue and he's considering getting twin 4 stroke OB's in the range of 200-250 hp each, but mount them on an Armstrong or D&D marine type bracket; this will mean WAY less fiberglass work (would have to patch transom shield hole) and will open up space inside the boat/deck. Fishing primarily here is trolling at 6-9 knots (Kauai); does anyone have some fuel numbers for a boat approximately this weight with twins? I know when you open these big OB's up, fuel disappears at an alarming rate, especially compared to a single diesel, but fast running here is not the norm (too rough). He's mainly concerned with all the pros/cons/costs of running twin OB's vs. a single diesel (not to mention the safety factor of having twin power with dedicated/independent fuel systems). This boat would be used to fish seriously (rough days/nights), also some fishing areas approx. 25-50 miles each way from home port. Any help & fuel numbers at various RPM's would be great; especially the range we're looking at (6-9 knots).
Thanks a ton,