is 20hp enough for a 35' fin keel yacht ?

[BlueSkyNick]

Re: is 20hp enough for a 35\' fin keel yacht ?

Last year, I replaced the original 35hp with the manufacturer's recommended replacement, ie 39hp. This is on a 34ft fin keel boat, so it is overpowered. When plugging into a sea or strong tide, this is a comfort factor in itself, ie I know its not under powered and will take us virtually anywhere.

The down side is that in normal conditions I run the engine at no more than 2200rpm, which is only half its maximum 4000. There is a general view that 75% of maximum revs is more healthy for the engine.

On balance, I would rather have plenty of power available when needed, and will worry about the engine speed in calmer conditions.

 

[Ships_Cat]

Re: is 20hp enough for a 35\' fin keel yacht ?

Hi BigNick

I think that you are doing the right thing and cannot see that any harm comes from running the engine well below max revs. Most (all, probably) pleasure boat engines are rated much higher than the same engine would be for commercial use, because pleasure engines get so little use in comparison. So a pleasure engine will likely last a long time in years (if not neglected) but not so long in hours when compared to a commercially rated engine. Furthermore, many commercial operators operate their engines in service at a maximum of perhaps 85% of the commercial rating so actually downrate them even further.

I would be quite confident that running a pleasure engine at revs well below maximum to achieve the same thing, probably has a positive affect on their life. In our own case we can motor into most anything at around 70% of maximum revs and comfortably cruise in flattish water at around 60% of maximum revs.

As you say it is a comfort to have some surplus power available.

John