The Beta 30 with 2.5:1 transmission will give you better performance than you ever got from the W30 (4-91). This calls for a 16"x12" three blade propeller.
If you go up to the Beta 38 with 2..45:1 transmission, the prop called for is 16"x13" three blade.
I worked on 16" propellers because that is what you currently have. If you can use a 17" diameter propeller, you will get slightly better performance.
The O'Day 37 is a very commodious boat but is not very heavy at 14,000 lbs dry weight. If you are loaded with everything for long distance cruising, the 38 may be the better choice. If the boat is reasonably light, the 30 will be more than adequate and will provide a boat speed of 7.5Knots.
Thanks for your quick reply Stanley - you really think the 30 would push it to 7.5? We never got more than 5.5knts from the westerbeke on a good day. If we're looking at a new prop as well - what would it be with a 17?
The old W30 was only 25HP when it was new and now that it is 30 years old it is down on power. If you use the correct engine and transmission combination with the right propeller, expect the boats performance under power to be transformed. It is a matter af matching everything to get the best results.
A slightly larger propeller will give better drive when you need power in a hurry. Ultimate boat speed will be the same.
