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Old 06-09-2010, 05:55   #1
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What Is the Right Horse Power ?

We have a Hallberg-Rassey 29. It still has its original Volvo Penta MD7B 18 horse power engine but that is coming up for 30 years old and we were considering replacing it with either the Volvo Penta D1-20 (18 horse power) or the D1-30 (28 horse power).

The boat has a sail drive and a folding two bladed prop.

The aproximate displacement is 4000K.

Which would be the better engine?

Which would be better for heavy weather? Manouvering in marinas? General cruising? Longevity?

Many thanks.
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Old 06-09-2010, 06:50   #2
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At 2 hp per 1000 lbs, 18 hp is the minimum engine for the boat, and the trend has been to higher hp over time. If you use your engine to get back on Sunday afternoon against a 25-35 knot chop, you will want the larger engine. If you just use the engine for manuvering and moving the boat when the wind dies, the 18 will be just fine.

Another big factor will be the amount of engineering it takes to fit the new engine in--modifying engine mounts and exhaust systems gets expensive, and a drop-in replacement will save half the cost of the new engine.

If you have to re-engineer, look at a Beta-- a bettter engine and without Volvo's piratical price policy on parts.
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Old 06-09-2010, 07:31   #3
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Kene, I agreed with Don. We have 31ft and sligthly more displacement, infact a lot more when loaded up powered by a 28hp Volvo 2003.

Engine normally runs at 2200 revs for 5.5 knots and slips diesel, sounds very relaxed and unstressed. But will go to 2800 at 6.5 knots if we really need to get home. Done this once when faced with a F7 developing on the nose.

We will have to repower at some point and it will be with 28 hp. The volvo has a 115 amp alternator as standard btw oh and I wouldn't go by retail prices. There is a recession on and deals to be done, especially if they can do it Autumn / Winter rather than Spring.

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Old 06-09-2010, 08:19   #4
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The two posts above outline all the real issues. Our boat normally came with a 46 HP engine on a displacement of 18,500 lbs. There was an option by the factory offered for a 64 hp engine. The PO jumped on it (lucky me). With 25 - 30 knots into steep chop the autopilot holds the boat and crashes through the waves under power. In calm waters the 1800 to 2000 rpm range hums along nice but crank it up to 2600 and it does go a little faster. The boat hits hull speed in calm water before the rpms max out and the fuel consumption goes up almost double. The point is for calm water the boat is over powered and the power is not being translated into speed but is instead plowing water. In a choppy sea I can't get close to hull speed without the extra power. This is when it is significant.

if you have ever powered into chop and suddenly found that 4 or 5 huge bounces of the bow drops your boat speed over ground to zero the extra engine power will help you maintain boat speed and not lose steerage. Losing steerage make a very bad afternoon.

Re engineering the engine mounts and drive train is something you should get help with. Some engines replace better with others not so much as being better but you need to attach all the stuff mounted to the engine and it all has to fit inside the boat. Some engines may allow you to reuse components too. It's also a good time to look at alternators since the bigger engine could support a larger alternator and make more electric power for battery charging. Also be mindful of your fuel tank because at high rpms your fuel consumption can double while at lower rpms perhaps increase just slightly.

This isn't cheap if you have to do it all. If you are re powering, consider your overall boating plans and if you are really in love. If you are not looking to cruise it probably won't be worth it. Selling the boat and starting over is the alternative to weigh seriously.

This is a moment of truth in a boating / banking relationship. Also note: The admiral knows a really stupid idea when she hears one. Relationship problems have a habit of cascading into other relationship problems. Save yourself and plan carefully.

I know several people with larger engines than stock issued and they all like it. It's not that you sail any less but you travel easier and safer. The not being there to begin with is the smart move but with enough time it happens anyway even doing that.
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Old 06-09-2010, 09:51   #5
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Originally Posted by donradcliffe View Post
without Volvo's piratical price policy on parts.
I'm going to take issue with this comment.

A rebuild of an MD7 is not expensive. There are several places online to look up the parts.

Now, go price parts for any other 30 year old engine that's been out of production for 20 years. Then come back and tell us how high the prices are in comparison.
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Old 06-09-2010, 10:06   #6
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I vote for more power. I have two twenty-eight hp diesels on my catamaran, and on more than one occasion, I had them at full throttle going into 38 knots of wind dead on the nose. It happened one time in New Zealand, and once in the Red Sea. Without the double horsepower, I would have had a real problem. As far as I am concerned, I can't have too much power on any yacht that I have owned.

If I ever went back to my old Westsail 32, the first thing I would do is put a 45 hp diesel in the engine compartment.
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Old 06-09-2010, 11:04   #7
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I agree with Dave.

For a full displacement hull, the right horsepower is the amount of horsepower it takes to get your boat to hull speed or near hull speed.

How this is determined is by formulas that can be found for your boats length, displacement and hull form or similar hull form. Doing this takes any guesswork out of the decision.

I would not put a Volvo back in. Not for what they charge for their parts, the time it sometimes takes to get their parts and their poor worldwide distribution network.
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Old 06-09-2010, 11:22   #8
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Thanks

Well, this thread has been a bit of an eyeopener. Last time on the scales, if they were accurate, my boat 33' steel cutter came out at 10.5 tonnes, which if i used the right calculator comes to just over 23,000 LBS. Always thought the 27 year old 20hp bukh was a bit lacking going into any kind of wind.
So thanks for making me feel a bit better about somehow finding the money for a new one. Was thinking of 39Hp yanmar. But don't wish to hijack the thread either.
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Old 06-09-2010, 14:44   #9
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Having never owned a boat with a Volvo engine, my information is all second-hand and a bit dated, so I considered the comment on Volvo parts pricing a bit of a troll...

Just to refresh my opinion, I did a google search and came up with the very interesting website Skipper product information worldwide which rates and compares engines, as well as other boat equipment. The website based a lot of their Volvo comments on interviews with the Caribbean charter companies, who have all switched away from Volvo engines.
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Old 06-09-2010, 15:06   #10
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Quote:
If I ever went back to my old Westsail 32, the first thing I would do is put a 45 hp diesel in the engine compartment.
Actually Dave the 45 isn't that much. My old CSY 33 has 35 hp and it wasn't enough. A few boats had 50 hp that would be left over when they were making 37's. The 50 hp on that boat was about right. The "standard" engine was a 29hp. Clearly way underpowered. A Westsail 32 is about the same tonnage as a CSY 33.

Quote:
The website based a lot of their Volvo comments on interviews with the Caribbean charter companies, who have all switched away from Volvo engines.
Not sure that alone is worth much to a single boater. Charter companies do a lot of odd things based on the business and the process of fleet management. International distribution and other financial advantages not used by a single engine buyer. Supply and pricing and a lot of other factors come into it. When you get into looking at engine evaluation it might be nice for new boats and new engines but to extend the brand name across a whole product line gets to be a pretty far reach.

Even at that when I went to the site it seems more like a wannabe Practical Sailor. The reviews were pretty worthless. Most of the reviews are 8 years old.
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Old 06-09-2010, 15:44   #11
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Quote:
Originally Posted by donradcliffe View Post
At 2 hp per 1000 lbs, 18 hp is the minimum engine for the boat, and the trend has been to higher hp over time. If you use your engine to get back on Sunday afternoon against a 25-35 knot chop, you will want the larger engine. If you just use the engine for manuvering and moving the boat when the wind dies, the 18 will be just fine.
I assume Don meant to indicate 2hp per ton.

As Don said, if you are daysailing, what you've go is probably fine.

If you are weekend cruising and need to be back at a reasonable time for work Monday, a larger engine might be the answer, but I would be inclined to motorsail with the smaller engine up to 25kt or so, you would probably do as well as motoring. Much more wind and I would be looking for a friend to pick me up at the nearest port.

My feeling is that if you are going off shore 2hp/ton is probably fine depending on hull shape.

If you are offshore you be shouldn't trying to keep to a schedule. If you can't learn to wait out the weather you will be getting yourself into trouble sometime that more horsepower will not cure.

I know there are atolls in the Pacific where the prevailing winds create a heavy current and chop that will run continuously thru the atoll's only pass for weeks at a time. In this situation motoring upwind will be the only option. There aren't many places where this is the situation. All the other situations I can think of where the wind and current will be against you and manueverability limited are tidal so you just need to wait for the tide.

The tradeoff for the smaller engine is better range for the same weight installed. A larger engine is going to mean a heavier installation for the same sized fuel tank, or a smaller tank. A smaller engine means you can motor at a much reduced speed (4-5kt extending you range even farther) without putting your motor too far out of its comfort range for RPMs.

All this said, I think I hold a minority opinion.
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Old 06-09-2010, 18:46   #12
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Assuming you made the decision to repower and your are selecting the D1-20 or D1-30 I would go with the D1-30.

I expect the incremental costs are negligible, the increased full burn when pushed is negligible and as any mechanic will tell you, "There is no replacement for displacement."
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Old 06-09-2010, 18:58   #13
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This isn't cheap if you have to do it all. If you are re powering, consider your overall boating plans and if you are really in love. If you are not looking to cruise it probably won't be worth it. Selling the boat and starting over is the alternative to weigh seriously.

This is a moment of truth in a boating / banking relationship. Also note: The admiral knows a really stupid idea when she hears one. Relationship problems have a habit of cascading into other relationship problems. Save yourself and plan carefully.
Wiser words were never spoken. I am all of a sudden realizing the same thing. I am looking at replacing an ending in a boat that will still need a total refurb of the interior, and a new mainsail, at a cost of about $20-25K so I can sail to the atlantic, down to the Panama and into the pacific when there are already boats more or less ready to go sitting in BC or Mexico at a comparable price plus a bit.

Suddenly I find myself wondering what the heck I'm thinking?


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Old 06-09-2010, 19:13   #14
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It's fundamental. Do you want to sail or fix boats?

I am not wired for a 2-3-4 or 5 year refit. I admire folks that can plan 5 years ahead but I definitely could not.

You trade money for time. I have no problem buying a pretty good boat and doubling the purchase price in refit. But that refit will be done with hired labor for the most part and take no more than 3 months.
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Old 06-09-2010, 19:13   #15
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Suddenly I find myself wondering what the heck I'm thinking?
It's a good moment to see the bigger picture. It's not that it's a bad thing but it should provide confirmation and lead to a better solution maybe both.

Looking at it that way - you can't lose unless the admiral is really ticked off. That was always looming for all scenarios. Boats in Mexico only look better when you are still in California and not in Mexico. On the east coast we have the same scenario and we call it Florida. Somehow the warmer weather makes the boats look better and cheaper.
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