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Old 18-03-2014, 14:11   #1
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Repowering? Bigger is better?

Or maybe go down in size?

My boat's displacement is 18,000 lbs on about a 33' 6" waterline and came equipped with a 44hp Universal.

I have been looking a little bit at repowering with either the Beta 43, or possibly the 38 and besides the knowing the fuel consumption should be better, the thought of saving 160 lbs worth of engine weight is very attractive to me.

Say what you want about me and weight but let's assume I would rather have bigger batteries working for me all the time instead of a bigger engine that just sits there doing nothing most of the time.

I'd like to think that the reduction in hp wouldn't be an issue for us given our sailing style, but I am at a loss to quantify both the potential savings in fuel consumption as well the real difference in speed under power.

Anyone have any ideas?
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Old 18-03-2014, 14:44   #2
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Re: Repowering? Bigger is better?

With a 18,000 lbs displacement on about a 33' 6" waterline and a LOA of about 40' 44 hp would be considered by some to be on the small side.

So it may depend on your projected use and how you like things the way they are.

However if getting a move on in difficult conditions, meeting a schedule, racing against the weather or punching against wind and tide are in your future downsizing may not be a good idea.

Depending on what will fit (do check your propeller shaft and aperture sizes) I would have thought that double your present power would not be totally out of line for a moderately heavy cruising yacht.
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Old 18-03-2014, 14:47   #3
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Re: Repowering? Bigger is better?

I guess it depends on where you motor, coming in the Hillsboro Inlet in Broward County FL all 24 horses are needed to turn the 3 blade prop to push my 10,000 lbs. Not sure what conditions are where you are. Would guess there is a difference between North Shore and South Shore sailing.

Wonder if operating the existing engine at 80% would be the equivalent of the reduced HP?
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Old 18-03-2014, 14:53   #4
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Re: Repowering? Bigger is better?

Beta Marine has a pretty good forum on their website and Farron and Stanley helped me to pick our Beta 38 for our 20,000 lb, 29' waterline offshore cruising boat. Of course, we were really underpowered with a Volvo 28 previously. Be aware that if you consider a Yanmar 40 (another choice I looked at) they require a 3" exhaust hose. At least last I looked. It has been two years.
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Old 18-03-2014, 14:54   #5
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Re: Repowering? Bigger is better?

44 hp at what rpm? Personally I would size my engine for the HP I need at about 2500 rpm. 38-44 hp at that rpm should be fine for your boat. But if it's rated at 3600 rpm... who wants to run up there? Too much cavitation up there in a heavy chop when the prop needs to bite good. JMHO
My 44 ft cutter had a Perkins 4-108in it and it worked great. A bit strange seeings how the engine was only rated at 51 hp. It was economical and pushed the boat great thru everything. Probably due to the Max Prop and 39 ft waterline to a large extent. I never ran over 2600.
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Old 18-03-2014, 15:56   #6
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Re: Repowering? Bigger is better?

The Universal M-50 is 44hp @ 3000rpm, very close to the Beta 43 43hp @ 2800rpm. If the Universal worked well so should the Beta. I replaced a Perkins 4-108 with the Beta 43 on my 22,000# ketch and I am very satisfied with the performance. The 4-108 was rated 50hp@4000rpm and at 3000rpm I doubt it makes 35hp.

+1 for Stanley at Beta Marine in NC, very knowledgeable and helpful.
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Old 18-03-2014, 16:05   #7
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Re: Repowering? Bigger is better?

Delancy, please tell us what percentage of max power (or r.p.m.) you normally cruise.

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Old 18-03-2014, 16:10   #8
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Re: Repowering? Bigger is better?

I have a Beta 38 on 24,000# boat (actual weight not brochure weight) with 32ft waterline. Call Stanly at Beta Marine. Nice people to work with and they stand behind their product. It's as important to get the right prop for best performance. If your boat actually weighs 18000# then it's hardly heavy. You can get the fuel curves for the Beta engines on their web site under each engine. Then you can calculate the savings from your existing engine. Tim --Northstar- Tartan 43
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Old 18-03-2014, 16:19   #9
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Re: Repowering? Bigger is better?

G'Day Delancy,

FWIW: OUr boat is a bit larger than yours - 46 LOA 44 LWL and heavy ship around 12 tons. Our engine, a Nanni 43, based on the Kubota V1902, has proven quite adequate for our usage (long term cruising). We use a Flex-O-Fold 3 blade prop, cruise at around 2000 RPM and 6-6.5 knots, depending on load and bottom condition and burn 2 1/2 litres per hour at that speed. We have never felt the need for greater power... sure, there have been a couple of extremes (moving about an anchorage in 50 kts) where more power would have meant greater speed upwind, but it did the job just fine.

I suspect that your proposed 38 hp Beta would be entirely adequate, especially if I read between the lines correctly about your sailing style. Talk of double the power is motor boat talk IMO... YMMV.

Cheers,

Jim
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Old 18-03-2014, 16:42   #10
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Re: Repowering? Bigger is better?

One rule of thumb is 1 HP per 500 pounds of displacement.

18,000/500=36 HP

I have three formulas that Gerr has published that use displacement and they spit out 36-38 HP.

Later,
Dan
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Old 18-03-2014, 16:53   #11
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Re: Repowering? Bigger is better?

I, almost installed a Beta 43 in my Cabo Rico 38. During my research I, spoke with a fellow Cabo owner who replaced his Perkins 4-108 with the 43. Said he was more than satisfied. Could cruise at 5.5 kts at 22 to 2500 rps current and wind dictating and was burning less than one gal per hour. This was in cruising load. Based on my boat about 11 tons . I did not replace my engine. Wasn't as big a problem as I first thought.
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Old 18-03-2014, 17:09   #12
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Re: Repowering? Bigger is better?

I just had to do the same decision process for a repower of a medium displacement 35' boat (Displ: 15000 lb and LWL 27').

I know others who have gone from the standard 30hp to 40-45 hp on this boat. I decided on a Beta 35.

I was tempted to go smaller, but the weight difference wasn't that great.

I think that going too big is a mistake. You'll put a lot more weight in the boat, and you'll end up running the engine at low rpms all the time. Remember, we're displacement hulls. There's a huge fuel cost in trying to go even a bit faster. And diesels like to run at high rpms.

The only argument that sort of makes sense for going very large is that you can push into wind and waves. Which is fine if that's how you want to run your boat, but if there are wind and waves, I'll be sailing. It is a sailboat, after all.
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Old 18-03-2014, 18:04   #13
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Re: Repowering? Bigger is better?

Quote:
Originally Posted by Delancey View Post
Or maybe go down in size?

My boat's displacement is 18,000 lbs on about a 33' 6" waterline and came equipped with a 44hp Universal.

I have been looking a little bit at repowering with either the Beta 43, or possibly the 38 and besides the knowing the fuel consumption should be better, the thought of saving 160 lbs worth of engine weight is very attractive to me.
...
Your boat will never appreciate the engine weight loss.

My boat is nearly the same waterline length, 33'-9", but displaces 24,000 lbs. The Yanmar 3QM30 seems small for a boat this size, as it produces only 30 hp @ 2600 rpm (continuous) or 33 hp @ 2800 (1 hour rating). But at 1850 rpm speed is nearly 7 knots.
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Old 18-03-2014, 18:41   #14
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Re: Repowering? Bigger is better?

Just did the trial sail on an IP38, 33' waterline, 21,500 lbs, 40 or 44 hp engine depending on RPM rating, boat is over propped but still hit a little over 8 kts at 2800 RPM. That was all it would pull due to being overpropped, but I doubt at that RPM it was making much if any more than 35 HP?
Your the same length but 3,500 lbs lighter, so I think 38 is plenty based on what I saw with the IP
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Old 18-03-2014, 18:55   #15
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Re: Repowering? Bigger is better?

Thanks for the feedback. As far as the current engine goes I can't say much as in so far as the tachometer doesn't work, nor does my speed log, but the engine smokes horribly and craves oil without offering up much in the way of oomph when it gets me in and out to the dock. Unfortunately, I can't say the PO lavished the boat with boundless love in general and the engine was no exception.

I agree the distributor is really the person to consult regarding size. Thanks for the tip about the fuel graph as I missed that previously when looking at their website.

My gut tells me to go smaller if possible and it seems like given some of the responses, smaller might not be unreasonable, but how does alternator size or adding a crash pump factor into the equation? Refrigeration? Obviously they matter, but how much?

Kinda what got me going on the downsizing thing was a comment made by daddle on a related thread about how he had a Beta 38 on his Santa Cruz 50 which has a similar displacement.
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