Repowering a 25D

[Ray Worthington]

I posted a similar message some time ago about being under-powered and not being able to get more than about four knots at 2800 rpms. I got several replies which told me that I needed to get my prop repitched.
I've had the prop repitched and now I get about 4.2 knots at 3200 rpms. I really think that a Yanmar 1GM of 6.5 hp is not sufficient power and would like to get an engine with around 12 hp. Has anyone repowered a 25D, and if so, with what engine, and what were your results?



acw@thebest.net

[Ken Cave]

Are you still using the same two bladed prop? If so, change to a three and have a professional prop shop reconfigure the prop for you.

I have seen several Dape Dory 25D (almost purchased one!) that did a lot better than you are doing now.

John Vigor, a frequent visitor on this site, changed his prop to a three bladed one-great results!!

Ken Cave



bcave@whidbey.net

[David Brownlee]

This sounds odd. Our Cape Dory 27 has a Yanmar YSM8 (7hp), which pushes the boat at 6 knots at full throttle in still waterh and cruises at 5 knots at about 3/4 throttle (no tach, sorry). This is with the standard two-bladed prop.

David Brownlee





dbrownle@sas.upenn.edu

[Bill]

@ 2500 rmps my 1GM pushes rhapsody at about 5 - 5.5 knots. It will be interesting to see if that improves once she gets her new bottom job (old paint is 3 1/2 yrs old).

Bill

I posted a similar message some time ago about being under-powered and not being able to get more than about four knots at 2800 rpms. I got several replies which told me that I needed to get my prop repitched.
I've had the prop repitched and now I get about 4.2 knots at 3200 rpms. I really think that a Yanmar 1GM of 6.5 hp is not sufficient power and would like to get an engine with around 12 hp. Has anyone repowered a 25D, and if so, with what engine, and what were your results?

cd25d@rhapsodysails.com

[Louis F. Ostendorff]

Hi Ray;
My 25D, KARMA, was upgraded from a 1GM to a 1GM10 in 1997 by one of her previous owners. When I got the boat, I was the second owner after the upgrade; the hour meter only had 67 hours on it, so the engine was (is) still rather new. A new bottom job was done around the Feb-Mar '99 time frame, and the boat came with a 3 blade prop. I have never measured it for diameter or pitch, but it seems to be about 12" across; I would estimate pitch to be about 8" or 9"; there's a way to measure that also...anyway, I've never run the engine past 3400 rpms and can easily attain 6 knots according to the GPS measured speed. This has been confirmed by running between two measured bouys out in the river. The 1GM10 is a bored out version of the 1GM, giving it about 20% more HP; Its continuous output @ 3400 rpm is about 8 HP, more than enough for the 25D. However, you should be doing better with your existing setup. Something else is stealing your power, and you need to find out what it is, before repowering...
BTW, I got copies of KARMA's repower job with the 1GM10; it was done by a well known boatyard, and they did excellent work, but it still cost the previous owner about $10,000 !!! The cost of this kind of refitting can't be recovered by selling the boat; you've got to want to do it for yourself, and the long haul...
Lou Ostendorff
CD25D "KARMA"
'82, #63



louosten@ipass.net

[Lou Ostendorff]

Ray;
As a corollary to what I said before, and from all the posts on this board about propellers, engine rpms, hp, etc. It would be prudent to mention a vessel's speed curve. Last Fall I took a class taught by the local Coast Guard Auxilliary called 'Advanced Coastal Navigation'. It was geared a little more towards power boaters in that navigation, courses and distances were based on known rates of speed in one direction, normally the destination you're going to. Unfortunately, sailors rarely are able to sail directly to their destination, and must tack, run downwind, heave to, wait, etc. to get there. Nevertheless, they say that a 'good captain' should know his vessel's rate of speed in calm conditions, so planning and estimating your trip is more reliable. Here are some numbers I recorded for KARMA on a relatively calm day. By matching engine, prop, and vessel, you should be in the ballpark with these numbers. If not, you're getting a 'power drain in the core' as they say on Star Trek!

RPM Knots
------ -------
1000 1.7
1500 2.7
2000 3.6
2500 4.5
3000 5.3
3400 5.9

As I said previously, 3400 rpm is the highest 'continuous output' that you're supposed to run these YANMARS (1GM10). The 1 hour rating is 3600 rpm, but I haven't been up that high yet.
Hope some of this helps....

Lou Ostendorff
"KARMA" CD25D
'82, #63



louosten@ipass.net

[Don Sargeant]

Perhaps your knotmeter needs re-calibrating

Don Sargeant
~~COQUINA~~

I posted a similar message some time ago about being under-powered and not being able to get more than about four knots at 2800 rpms. I got several replies which told me that I needed to get my prop repitched.
I've had the prop repitched and now I get about 4.2 knots at 3200 rpms. I really think that a Yanmar 1GM of 6.5 hp is not sufficient power and would like to get an engine with around 12 hp. Has anyone repowered a 25D, and if so, with what engine, and what were your results?

[Jack Aboulafia]

I was reading a reply by Ken Cave that John Vigor went to a 3

bladed prop on his 25 D with great results. If John ,or anyone else ,has more information on the 3 bladed prop(pitch ,size,is it a sailing prop) ,please e-mail me.




Indianahundred@yahoo.com