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Wow, all that stuff in such a little casing.  So much opportunity for "Whoops, seem to have a bit left over"

Today I did some investigating and thought you would be interested in the results.  A friend had the brilliant idea of using an optical tach on both the engine and the gearbox output, so I borrowed one from work.  The Hurth transmission manual on this website indicated that there is a label on the trannie to show what the ratios are forward and backward.  Great stuff.  I should have mentioned before, that I have a 25XP engine.

After a number of interesting contortions with mirror in one hand and flashlight in the other, I concluded there was no part number and no ratio label on my trannie.

I went ahead anyway with runs in neutral, and in gear, loading the engine by trying to pull my helical mooring out of the ground, first in reverse, and then forwards.  I didn't have the courage to pull against the mooring at max rpm.  I concluded that the boat tach was reading a bit low, and assuming no slip, calculated the gear ratios.  It just so happens that the calculations closely match the example shown in the manual (1.86 reverse, 2.05 forward), so I'm concluding no slip.  Max true engine rpm in neutral was 3217.

Then I went out and did some motoring.  There was just me, and I wasn't prepared to go below for long enough to make measurements, so I had to content myself with using the measurements on the mooring to estimate true rpm from the ship's tacho.  Two main conclusions were my knotmeter is under-reading by about a knot, and the max rpm under load is 3125 indicated, 2952 estimated actual (i.e. a loss of 265 rpm due to load).  Running at 80% of this value gives a true speed of about 5.1 kt.  I'll try to attach an excel spread sheet with all the details - I may be successful or not, but thank you for your interest and help.

Moored neutral   Tach   Eng rpm   Tran rpm    GPS   knotmeter              tach o'read      
                   1130   1076                                    idle           5%      
                   1500   1445                                               4%      
                   2000   1881                                               6%   Tach over-reading about 5%   
                   2500   2380                                               5%      
                   3350   3217                                    max rpm   4%
      
Moored reverse   1100   1016            546                         idle           8%   Gear ratio    1.86
                   2000   1896            1013                                    5%   Gear ratio    1.87
Moored forward   1100   1034            508                                    6%   Gear ratio    2.04
                   2000   1900            932                                    5%   Gear ratio    2.04

Motoring forward      estimated                                     % max rpm      
                   2400   2286                   5.0   4.0                      77%      
                   2700   2571                   5.5   4.5                      87%   Ktmeter under-reading by ~1 kt   
                   3100   2952                   6.3   5.0           max rpm   100%      
                           

Thank you for your replies.
Tacho calibration:  Was done a few years ago when I upgraded the alternator.  At that time max rpm was just about 3000, so I'll check if that's still the same.  I'll check David's other speed/rpm thoughts at the same time.
The 2-bladed prop is clean and appears fair.  It was professionally repaired, faired, and balanced about 3 or 4 years ago after it hit something, so I think it's alright.
The only wind was the wind due to my motion, and current there was a little, possibly half a knot, which may explain the difference between GPS and knotmeter.
And the oil was clean.  Not sure if I'm pleased or not - if it was black that would probably give me the answer, expensively, but being clean leaves me still in doubt.

I will have a go at it this weekend.  I'll run across the wind in a current-free area and check knotmeter, gps, and tacho in both directions.  See what that turns up and let you know.
Thanks
John Gardner

Today I set out on a windless day, so engine on.  I'm sitting off to the side so don't see the knotmeter, but after a while the penny drops that with the engine rpm at my normal 2300, I'm only doing 4.3 kt.  Normally it's 5 point something, and it seems to me, now that think of it, that a few years ago it was more like 6.  I anchored and dived on the propeller - nice and clean and no dings. 
I checked the transmission oil level - right on the money.  The speed sensor is nice and clean and although it was reading lower than the GPS, it was only half a knot off.  The bottom was painted this winter and is nice and clean.  I haven't checked whether anything is wrapped round the keel - the Chesapeake is so murky, you can't see the keel from the propeller, and the possibility didn't occur to me till later, but in any case it's unlikely.  There's not many possibilities left.
Comments and wisdom would be much appreciated.ner
John Gard

I find that Velcro adhesive is liable to fail after a time and in the heat of the summer.  I've successfully used the combination of a very small panel pin to take the weight of the picture and a 3/4 x 3/4 piece of Velcro at each corner to stabilize it.  Nothing has fallen yet in the last 7 years.

Thank you.  John

On a recent visit to the top of the mast to drop a runner to feed in a new jib halyard, I noticed that the two sheaves on the forward side of the mast were seized or nearly so.  I couldn't be sure of the material - plastic or aluminum.  After a bad experience once before when I greased a plastic spacer in a winch, that then swelled and became hard to turn, I am very cautious now about what I lubricate and how, so I didn't yet apply any oil to the sheaves.  Can anyone tell me what is the material of these two sheaves?

John Gardner

I've had good success spraying my Vetus plastic ones with an aerosol can of Vinyl and fabric paint - intended for car seats and the like.  Did them two years ago and it is holding up well.

I went looking at the rudder post and found the top and aft side perfectly dry.  The forward side, down in the dimple looks a bit as though it might be weeping.  Difficult to see with the water tank in place, and I can't think why damage would occur in that place.  Have to wait for winter haul out to look further.

Meanwhile here's a photo to supplement the very good sketch Stu found.  It may be helpful to someone.

I think the valve is a non-return valve from the shower drain, to stop shower water flowing back into the shower tray from the higher line up to the anti-siphon valve.  Itwill allow water (or air) to flow from the shower toward the through hull (and potentially to the toilet) when it is working properly.  I think more likely is a blockage in the through hull (weed, plastic bag?).  What happens when you pump out the shower?  Does it go into the toilet bowl?  That would confirm a blocked through hull.  If you're lucky, it might clear the problem.

George,

It's a fixed two blade prop.  The original to the best of my knowledge.

Yesterday I managed to put a 1" spacer between the engine gearbox and the bullflex coupling.  I went for a swim and I have about a two inch space between the prop hub and the strut.  However, it didn't give much, if any further improvement.

John

Some experience for you that may or may not be relevant.

Always, but especially during the last two or three seasons I've had vibration from the propellor shaft, to the extent this season that it limited the max rpm I was prepared to go to (about 2000 rpm - quite speed limiting).  The nature of the vibration is like a pair of engines that are not quite synchronized - the intensity/volume of the vibration comes in waves on a cycle of every 2 seconds or so.

The prop was repaired and balanced after meeting a log a couple of seasons ago, so I was confident in the prop.  The cutless bearing is in good shape.  Last winter on the recommendation of the boat yard I removed the Vetus engine mounts I had put in and put back the original style mounts (wouldn't you know - it was just a couple of months after I had thrown the old ones out).  I didn't do as they recommended and replace the Vetus Bullflex coupling.  However, I re-checked the alignment of the engine.  This season, no improvement.  I wondered whether harmonics were being set up between the prop and the prop shaft strut - I know there is a minimum distance one is supposed to have because of this problem - so I slid as much of the prop shaft out of the coupling as much as I dared (about half an inch) and tried it out.  Vibration is much reduced. I don't know what distance I have there now; unless I go swimming, it will have to wait till winter.  Since I now have only about 1 inch of engagment of prop shaft in coupling, I am trying to dream up a way to push the prop shaft back a little bit further in the hope of totally eliminating the vibration.

But the point of this ramble is...don't forget to ensure there is good separation between prop and strut.  (Maybe someone else can recommend a distance, but I'm presently aiming for a couple of inches.)

Thank you Stu, that's just what I wanted.  I did look, honest, and as a result I've read all about leaky rudders, but I didn't find this.

Ken, I spent a fair bit of money with the boat yard last winter digging into the glass around the strut, only to conclude the water was not entering that way.  From the inside, the rust around the bolts makes it look as though water is coming in through the bolts, but when some of the fiber glass was cut away on the outside, it was clean and dry, so we gave that up.  I decided the rust was resulting from water dribbling past the bolts from the dimple.

Thanks for the thought.

I am getting salt water in the dimple aft of the propeller shaft support securing nuts.  I can't think that it is coming from anywhere other than the rudder post.  Unless someone perusades me that there are other options, it looks as though I shall be exploring this area over winter this year.  Can anyone give me an idea of what to expect, what to look for?  Am I right in thinking that the rudder stock is in a fiberglass sleeve/housing that is part of the hull and extends above the water line?  I think I've read that there is a gland at the top of it.  What is that like, how does it seal - is it like a propellor shaft stuffing box?  Assuming I have to do something there, I presume it is not necessary to have room to drop the rudder? 

If you've been following the above thread, my recent experience will amuse you.  I just put in a couple of cleats a couple of weeks ago, and completely agree or completely disagree with various items above!  But for a for the end result, see photo (attached I hope):


From Defender:

Item Description: SUNCOR TRIMLINE CLEAT 316SS
Item Number:      012177
Quantity Ordered: 2
Price Each:       $25.99
Precision Cast 316 Stainless Steel
8" long; 1/4" fastener holes (4)
Model #: C3208-0000

So I installed 2 stainless steel 8 in cleats each using four ¼ in stainless steel bolts.  Each was installed with an aluminum backer – I happened to have some 1/8 in thick aluminum alloy plate, and I cut two backers each 2 ½ by 4 ¼ in.  I  pre-drilled the plates to match the cleats.

When I started this little project I had only one access port in the front wall of the anchor locker.  (See photo)  I found that if I thrust my left arm including elbow right inside I could then bend the elbow and get tenuous access to the area where the bolts for the starboard cleat would be.  (I never did the Charles Atlas course, but those that did it, or didn't need to, might not be able to manage this contortion.)  Since I have a propensity for cutting things the wrong length, I checked everything 3 times, drilled the first hole, put the cleat in position with one bolt dropped through, and drilled the other three holes.  A quick check and a sigh of relief that the backing plate did indeed fit, and everything looked like it should.  Chamfered the holes, put sealant in and installed the cleat and bolts.  Then came the fun bit of getting the nuts and washers on.  By the time I had thrust my arm in the hole twenty times due to dropped nuts and washers and for this or for that, my knuckles were beginning to get a bit bare through scraping on the unfinished fiber glass.  Eventually the nuts were on, and starboard was finished.  As suggested above, I had the backer plate and the wrench on strings, but I soon found that the washers and nuts that I dropped ended up in the bottom of the bilge under the forward bunks.  Half a dozen assorted nuts and washers were all recovered without problem.

The port cleat was a different kettle of fish.  The position of the Beckman access port is not central in the boat, and the port side of the anchor locker does not have a shelf let in for a small anchor.  There was no way I could get my right arm to the area where the cleat bolts would be.  I had to put in another access port under the cleat.  Out with the reciprocating saw and a hole was cut.  For some reason, (previous boat maybe) I had in mind that the wiring to the forward nav lights was in the starboard side.  Not even when saw hung up on something did the light dawn.  Only when the disk of fiberglass came out did I realize the stupid truth.  Duh!  I put the new Beckman port in – that was easy, and installed the port cleat.  Same sort of process as for the starboard – a lot easier this time, but still requiring plenty of patience and dexterity.  And then I repaired the wiring.