>> Can someone give me an idea about prop specs and what I should expect for a cruising speed, fuel usage and top speed. Of course, GB can probably give you a good estimate of performance with the various Cummins Engines, but for talking purposes, we can crunch a few numbers. If you're technically inclined, you can work through the calculations using Dave Gerr's book "The Propeller Handbook". The spec displacement for a new GB 46 is 39000 lb (I assume empty). Let's say your cruising displacement is 43,000 lb. A pair of 370 HP engines will deliver 710 shaft HP (2 * 370 * 0.96). This will yield a "mill pond" velocity of 19.3 knots at WOT. I made this estimate with Crouch's equation for planing hulls: Velocity[knots] = 150 * (shaft HP / displacement[lb])^0.5 In less than optimal conditions, you will probably get a reliable 18 knots at WOT. You say your current engines are 210 HP Cummins BTA-5.9s. At WOT, what RPMs do you get, and what velocity are you making? What are your props (diameter and pitch, number of blades)? What is your transmission ratio? Another thing, the Cummins 370 is an interesting choice of engines. If you compare the 370 to the 330, you may find the 330 is better choice. Both engines have the same block, crank, head, and pistons, and the maximum sustained cruising RPM of any B series engine (in my opinion) is around 2400 rpm. If you compare the prop demand curves of the 370 (370 hp at 3000 rpm) to the 330 (330 hp at 2800 rpm), you will find that the 330 is actually providing more power at realistic cruising levels. For instance, using a prop factor of 2.7: RPM B330 B370 ----- ---- ---- 3000 n/a 370 2800 330 307 2600 270 251 2400 218 203 2200 172 160 Note that at 2400 rpm, the B330 will be making 218 HP and the B370 will be making only 203 HP. With the same transmission, the B330 will use a higher pitch prop. To achieve the same cruising speed, the B330 will run at a slightly lower RPM. Now consider that the B330 is a significantly less expensive engine. In my opinion, the 370B is the best engine for boats where top speed is most important. The 330B is the best engine where cruising speed is most important. Thus, my choice for a GB or any other cruising boat, would be the 330. Of course, if you want to RACE your GB, the 370 would be the better engine. Don't laugh, people try to race all kinds of boats. I've even heard that on the coasts they try to race sail boats :) Jim Bohn M/V Margaret Ann 1974 Trojan 44