Yanmar 30 hp or 45 hp

[M47]

Have to re-power my 25,000 lbs 45' catamaran, two engines. Decided to stay with the Yanmar brand. Engine "room" space is not a huge issue. Mostly coastal cruising, but still getting into situations on rare occasions. Motor-sail about 65% of the time. Should I go with 30hp or 45hp? Extra wieght is about 150lbs, consumption almost the same, acceptable price difference of about $5.5K.

[Cheechako]

You might ask yourself what rpm you like to run at. I hated running my Yanmars at the high rpm they recommend. That's how Yanmar gets their rated HP.... by rating at high rpm. If you need 30 hp then what rpm on the bigger engines produce that? So I lean toward the bigger engines. My 42 cat had 3GM30's... I thought they were a bit underpowered at times..... but they are not 30 HP engines like some think.

[a64pilot]

My 4-JHE is 44 hp, 40 continuously.
For reasons of NVH an automotive acronym that stands for Noise, Vibration and Harshness, I don't like to run it over 2,000 RPM, at that RPM it's a 20 HP motor.
I wish I had a larger motor so I could cruise at hull speed without my boat sounding like a lawnmower.

[M47]

Normally, I tried to stay 2300-2500 rpm on 30s. Not much speed, but reasonable fuel consumption, one engine at the time.

[StuM]

I agree with Cheechako and A64Pilot.

Mine's a similar sized cat, I have 2 x 40HP Yanmars and wouldn't want to go down to 30's. The 40's have enough power to allow me to run on a single engine in most circumstances without A64's NVH. If I had 30's I'd probably need to run both engines together a lot more.

And there have been situations in adverse conditions where I've run both at high revs. It was very nice to have the grunt when it was needed.

[Moontide]

Have the 3JH Yanmars (37 hp) on a 47' cat. Hardly ever run two engines so I would go with the 45 hp. With 30 you'll need to run both to maintain any type of speed.

I would suggest you look at the Beta's also. Have only heard good things about them. Probably longer than Yanmars so space might become an issue. (No financial interest, and not even a customer).

Bill

[YARGESOL]

I have 3GM30 on my 46 cat (laiden about 25000 lbs). When it will come to repower will definitly go higher.My 27x2=54hp are good on a calm conditions and by the wind (thought,than all sails should be on).But,when I have 20kts upfront....than it's really underpowered

[boatbod]

Shaft or sail drive? If it were me, I'd go with the larger engines on a shaft drive, or the smaller if SD20 sail drive. Do anything you can to avoid SD50 & SD60 sail drives.