Engine Size

[malbert73]

Why only 30 hp if you’re going ahead and repowering? Betas are awesome!

[Suijin]

If you can’t motor into a 35 knot headwind and associated wind-driven water, you’re underpowered.

That’s my criteria after taking two hours to go two miles up the entrance into Norfolk during a freak winter storm in December a few years ago. 44 hp in a 40’ 14 ton boat.

If I’d not been able to make headway I would have had to run out to sea. Not so bad but the temps were going down to 15 f. I was glad to make it in.
Then again Sean on Alexandra has circumnavigated without an engine. I expect if you’re cognizant if what your boat can and cannot do and plan accordingly, you’ll be mostly fine.

[kristjan]

Originally Posted by malbert73

Why only 30 hp if you’re going ahead and repowering? Betas are awesome!

Mostly because more isn’t necessary as an auxiliary engine. It’s enough to motorsail on tick over for a long time. If I can motor 5 knots in a bit of head wind I’d be happy, if winds are more than contrary I’d use it to motor sail to alternative location.
Even the md17 gives me much more guts than needed, and I can tell the engine is worn out.

When people talk about needing a big engine to get to safety, I think they often haven’t evaluated all the options. Doxy, for example has excessively heavy tackle and anchoring in some shelter is also a solution to not making ideal destination.

I suppose it’ll come down to dimensions really, and I haven’t closely measured. My engine space is a little tight, the md17is quite cramped in.

[malbert73]

Great points and illustrates difference in objectives. I repowered this winter- beta 50 is same block as 43 so weight difference minimal. I like the option to power at 1900 rpm at 7+ knots in light/no air. I don’t really use the safety argument much. If wind is up my boat sails upwind really well (with nearly 9 foot draft with board down I can claw upwind well) but I like convenience of larger engine for making miles when I need to.
I mainly asked because the difference in weight and cost is pretty small once you are repowering. No one ever complains their engine is too powerful within reason

[Sailor 99]

Originally Posted by tkeithlu

Guys, hull speed has gotten too little attention and power to weight too much in this discussion. Reaching hull speed takes surprisingly little HP in even a very heavy boat. Exceeding it takes bunches. You're talking aout 40 to 45 foot boats. A 35' waterline has a hull speed of 7.9 knots, 40' waterline 8.5 knots, and a 45' 9.0. So, my 43' overall 30 ton boat does 6.5 knots at 1600 RPM, 7.5 at 2100, and 8.5 at screaming speed on a 140 HP engine. If you are staying at those gentle speeds, those of you with the seemingly small engines are doing just fine; those that have to fight a 7 knot current or want to beat a bridge closing are going to need a whopper of an engine.

this is not my exprience on my 20 ton ( real weight not brochure) 50 foot boat with a 38'7 water line. with a 67 hp motor @ 60% of max power in flat water doing 6 knots we use 4 ltr / hr @ 80% of max power doing 8 knots we use 8 ltr/hr.



A little over proped with a 20 inch x 13 Flex-o-fold 3 blade.




Hugh difference. As long as we are not battling wind and waves we are much more fuel efficient at 60% rpm