Repowering a 37 - SailNet Community
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post #1 of 18 Old 07-29-2010 Thread Starter
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Repowering a 37

I am considering replacing my aging 50hp Yanmar with a smaller Yanmar. My rational is that my engine is used for charging batteries, motoring in calm conditions and getting in and out of marinas. Under these conditions a 32hp engine would be much more fuel efficient, as well as being lighter.
Is there anyone who has a 37 with a smaller engine than the standard 50hp who wished they had a bigger one?. If so under what conditions?.
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post #2 of 18 Old 07-29-2010
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Hi Delivered,
We have a 1983 model Crealock 37 that has the original 32 Hp Universal 5432 (Kubota) engine with a three blade Maxprop. We cruise at 5.5 to 6 kts (flat water- no wind) and have a max speed of about 6.5 kts. Fuel burn rate is about 3/4 gal per hour at cruise. I have never sailed on a 37 with the larger engine, so I can't make comparisons, but 32 Hp has been very adequate for us.

Dave
Crealock 37 #151
"Eowyn"
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post #3 of 18 Old 07-30-2010
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We have a 1982 C37 and replaced the Universal 5432 with a Beta 38 hp and am very happy with the results.When powering into headseas the old engine seemed underpowered now the Beta with a 3 blade prop just blasts thru.At cruise speed 1800rpms 3/4 gall per hr burn.The new engine was also 150lbs lighter.
Dianne and Chuck Burke S/V NiftyNickers
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post #4 of 18 Old 08-02-2010
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Quote:
Originally Posted by delivered View Post
I am considering replacing my aging 50hp Yanmar with a smaller Yanmar. My rational is that my engine is used for charging batteries, motoring in calm conditions and getting in and out of marinas. Under these conditions a 32hp engine would be much more fuel efficient, as well as being lighter.
Is there anyone who has a 37 with a smaller engine than the standard 50hp who wished they had a bigger one?. If so under what conditions?.
I replaced the Yanmar 4 cylinder rated at 40/44 HP with the Yanmar 50/54 HP motor. Basically the same engine, I believe the the 40/44 HP had cylinder sleeves while the 50/54 does not and the bore was increased. The 40/44 HP was more then adequate. In communications with the factory it seems that the engine of choice is rated at 39 HP. I assumed it was the 3 cylinder Yanmar which probably has undergone a similar HP increase over the years.

The 50/54 HP motor was not quite the drop in replacement I expected as it requires a larger diameter exhaust system so that had to be replace and a larger thru-hull put in.

If I had a do-over I would likely go with the smaller engine. Sufficient HP, less weight in the stern of the boat. I believe the boat would balance out better forward/stern with a lighter engine. Crazy Fish has an SS arch, a 15HP outboard hanging on the stern rail, a Monitor Windvane,, 2 propane tanks in the locker and all the hardware for the WH autopilot below the wheel. When doing more then day sails there is frequently a couple of scuba tanks and associated gear stored in the cockpit lockers - so I am always looking at what is stored in the cockpit lockers and in the quarter berth and seeing what items can be moved forward to better balance the boat.

Regards
Marc Hall
Crazy Fish, Crealock 37, Hull 207, San Diego
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post #5 of 18 Old 08-02-2010
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Not sure if any other PSC owners feel this way but, if I were in the market for a PSC 37 and most of the more recent ones had the 50HP Yanmar and yours didn't, I'd summarily rule out your lower powered boat. The rationale being that PSCs are built/marketed to be "blue water cruisers" and the extra HP is deemed to provide a safety factor. I think of this engine as an improvement the builder made in the design over time, and you'd be in effect, undoing the improvement.
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post #6 of 18 Old 08-02-2010 Thread Starter
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Too those of you that have shared your experience with me to assist my decision, thank you, your information is useful. Taking your input I am leaning towards the 39hp 3 cylinder Yanmar.


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Not sure if any other PSC owners feel this way but, if I were in the market for a PSC 37 and most of the more recent ones had the 50HP Yanmar and yours didn't, I'd summarily rule out your lower powered boat. The rationale being that PSCs are built/marketed to be "blue water cruisers" and the extra HP is deemed to provide a safety factor. I think of this engine as an improvement the builder made in the design over time, and you'd be in effect, undoing the improvement.
I am a blue water cruiser with more than 30,000 miles under my belt in my PSC, most of it in the North Atlantic. So I live in the blue water cruising community. Very few of them consider fitting an overpowered engine as "an extra safety factor". Raw power is not a substitute for good seamanship. Like everything else on a boat engine power and weight is a trade off. As a blue water cruiser I consider the extra range of a smaller engine in calm conditions to be more of safety factor than the small incremental capability to bash away from a piece of land, which I should not have been so close to anyway, in bad conditions.

I doubt whether PSC had the blue water market in mind when fitting the larger engine with only a 140 litre fuel tank. In my selection process I had this marked down as a negative against the Crealock 37. It would be useful however for getting back to the club before the bar closes.

Last edited by delivered; 08-02-2010 at 05:17 PM.
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post #7 of 18 Old 08-02-2010
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You may also want to consider posting this question in the diesel engine forum (a sub-forum under 'Gear & Maintenance') where you may get a broader range of opinion.

I notice Nigel Calder's 'Marine Diesel Engines' has a nice discussion on this topic that considers a number of factors including displacement, propeller efficiency, HP losses due to use of auxiliary equipment loads, intermittent duty vs. maximum duty ratings, etc. etc.. Using the rule-of-thumb of 1HP per 500lbs of fully loaded displacement and assuming you're weighing in at under 20,000lbs (PSC '37 spec'd displacement being 16,000lbs), it seems you can certainly make the case that 39HP ought to do it given your preference of range over power.

In the interests of keeping costs and therefore selling price down, one would think PSC would follow this same logic to justify putting lower cost/weight engines in their boats, and yet they do not do this (of course many other manufacturers do however). For other PSC owners considering this same option, perhaps it'd be helpful to understand why PSC continues to go with the more capable engines. As a matter of my own personal preference anyway, I'm glad to have the extra power in reserve. Perhaps the Pardey's have it right though - maybe a bath tub would be a better use of that space altogether!
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post #8 of 18 Old 08-02-2010 Thread Starter
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Originally Posted by MC1 View Post
You may also want to consider posting this question in the diesel engine forum (a sub-forum under 'Gear & Maintenance') where you may get a broader range of opinion.

I notice Nigel Calder's 'Marine Diesel Engines' has a nice discussion on this topic that considers a number of factors including displacement, propeller efficiency, HP losses due to use of auxiliary equipment loads, intermittent duty vs. maximum duty ratings, etc. etc.. Using the rule-of-thumb of 1HP per 500lbs of fully loaded displacement and assuming you're weighing in at under 20,000lbs (PSC '37 spec'd displacement being 16,000lbs), it seems you can certainly make the case that 39HP ought to do it given your preference of range over power.
Nope, I am looking for people with real experience with this hull not theorists. The variables are too wide and subtle for anything else to make sense.
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post #9 of 18 Old 08-02-2010
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Seems reasonable. As you undoubtedly know, Nigel Calder had a PSC for many years. I also wouldn't understimate the value of the knowlege-base you have access to here on Sailnet. There may be a lot of theorists, but there's also quite a few marine professionals that tend to weigh in. You can usually tell the difference by the quality of the posts (e.g., I'm one of the theorists ).
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post #10 of 18 Old 08-02-2010 Thread Starter
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MC1 have you thought through the situations where you need that reserve of power. I would be interested to hear where you think you might need it.
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