Thursday, February 19, 2009

Repowering calculation...

TIH is a few years away from re powering at the moment. The correct engine size for a Whitby 42, however, is currently being discussed on the Whitby owners group.

This link is to an interesting spreadsheet which is worth downloading if choosing a suitable replacement engine. Please note the posters comments of the veracity, or otherwise, of the spreadsheet and you should check all calculations from another source.

The maximum hull speed for the W42 is 7.67kts. (Hull Speed = 1.34 * (LWL)1/2).

As usual there is no correct answer (but a few incorrect ones) about engine size, 55HP would appear to be on the lower end of the scale with 90HP on the upper end. What is interesting is the jump between 70HP and 90HP only gives you .25kt extra, in heavy seas.


1 comment:

rj said...

And, the frustrating thing is, there are very few marine engines on the market in the 70-100 hp range. All turbo charged and/or intercooled.

At least that is as of a year ago. I know turbos are more reliable these days, but I would still want a naturally aspirated engine if available (BETA and Westerbeke seem to be the only possibilities).

Plus, EPA emission requirements are becoming more strict next year. Not sure how that will impact the small marine market.