Over propped?

[joe_db]

As shown in the photo I posted, I am doing 6.2 knots in a bigger heavier C&C 35 with an Indigo prop. If memory serves, I was able to do at least 4 knots *towing a C&C 40*. There is something quite wrong somewhere.
My reverse is OK, not amazing, but the A4 is always going to be like that with the reduction gear. I recently had to back out of a slip in Rock Hall into a very narrow fairway with about 20 knots on the starboard quarter and managed to do so.

[indigo]

Rick,

The thought just occurred to me that since you have a C&C32, was it perhaps built in Canada? For many years a "de-tuned" version of the Atomic 4 known as the "Stevedore" was sold in Canada. This de-tuning was accomplished via the installation of an orifice about 3/4" ID in the manifold just above the flange where the carb attaches. I saw an image of the orifice arrangement recently but I cannot recall where. Perhaps someone on the Forum has an image.

This orifice effectively reduced the max HP to about 20 as I recall. That would completely explain your engine maxing out at 2100 RPM at 4.5 Knots.

Food For Thought.

Tom

[rickinnj]

Tom,

Thank you for your generous offer to pay postage to inspect my prop. I don't believe the prop was the issue with poor forward speed as much as a tired engine. Although compression is good and she starts right up since last winter's valve adjustment, I think 50 years of service deserves retirement. I've already reached out to Moyer about a long block and head to put in this winter.

I bought your prop to replace a crappy, sloppy old Martec folder which gave me nothing but trouble mostly concerning partially unfolding. The vibration was so bad that I broke a strut the first year I owned Anchovy. I was thrilled with the Indigo when I splashed that spring. No more vibration. Trouble free. The forward speed never really bothered me...I figured it was a function of the prop being so small. I honestly didn't know I should be going faster.

Then I started seeing dock mates controlling their boats into the slip with just shifting between forward and reverse without touching the throttle and wondered what I was doing wrong. All of these boats had feathering props. I just had to have one!

Last winter I plunked down a chunk of change on the Featherstream (by the way, it's 11x7, not 12x7 as I said earlier...still too much prop). I spent most of the season day sailing where I basically idled out of the marina and had sails up within 10 boat lengths. I was finally backing into my slip without throttling up. I had instant grip in reverse and had full steerage with half a boat length. It wasn't until we went on a week long cruise in August that I found out I had a problem.

I have been in touch with Darglow, and the are very interested in modifying the Featherstream with respect to modifying the blade chord width to reduce wetted surface area. The Indigo has a chord width of approximately 2 7/8" while the Featherstream is 3 3/4".

I don't know if the feathering prop will be workable and if not, I still have the Indigo that I can put back on. Either way, I still plan to repower over the winter.

That's my story and I'm sticking to it!

[joe_db]

Tom,

Thank you for your generous offer to pay postage to inspect my prop. I don't believe the prop was the issue with poor forward speed as much as a tired engine. Although compression is good and she starts right up since last winter's valve adjustment, I think 50 years of service deserves retirement. I've already reached out to Moyer about a long block and head to put in this winter.

I bought your prop to replace a crappy, sloppy old Martec folder which gave me nothing but trouble mostly concerning partially unfolding. The vibration was so bad that I broke a strut the first year I owned Anchovy. I was thrilled with the Indigo when I splashed that spring. No more vibration. Trouble free. The forward speed never really bothered me...I figured it was a function of the prop being so small. I honestly didn't know I should be going faster.

Then I started seeing dock mates controlling their boats into the slip with just shifting between forward and reverse without touching the throttle and wondered what I was doing wrong. All of these boats had feathering props. I just had to have one!

Last winter I plunked down a chunk of change on the Featherstream (by the way, it's 11x7, not 12x7 as I said earlier...still too much prop). I spent most of the season day sailing where I basically idled out of the marina and had sails up within 10 boat lengths. I was finally backing into my slip without throttling up. I had instant grip in reverse and had full steerage with half a boat length. It wasn't until we went on a week long cruise in August that I found out I had a problem.

I have been in touch with Darglow, and the are very interested in modifying the Featherstream with respect to modifying the blade chord width to reduce wetted surface area. The Indigo has a chord width of approximately 2 7/8" while the Featherstream is 3 3/4".

I don't know if the feathering prop will be workable and if not, I still have the Indigo that I can put back on. Either way, I still plan to repower over the winter.

That's my story and I'm sticking to it!

Don't let me stop you from buying a new engine, but do check for the Stevedore restriction. Also do get a manifold gauge ASAP, you need to know what the engine is doing. I can't get in or out of my slip shifting at idle, the A4 does not have enough thrust for that. Diesels have more low end torque, to the extent it can be a pain. One big motor yacht I had to deliver had something like twin 1200 HP diesels and did 7 knots *at idle*

[ndutton]

Last winter I plunked down a chunk of change on the Featherstream (by the way, it's 11x7, not 12x7 as I said earlier...still too much prop)

Says who and to what degree? The 12x7 might be a little aggressive but it's not terrible, certainly not so big as to be the sole cause of your performance problem. I'd guess there were well more than a thousand Catalina 30's powered with direct drive A4s and 12x7 two blade props from the factory that performed reasonably well.

[rickinnj]

Neil,

It's a three blade 11x7

[ndutton]

It's a three blade 11x7

With boats and engines our size the number of blades, 2 or 3, isn't dramatically significant in engine loading. You may find noodling with the prop size calculator found here to be interesting. At the end they make recommendations on diameter and pitch of props with different numbers of blades. I tried it, put in the parameters of my boat and engine, the prop sizes it returned were virtually the same , 2 blade or 3 blade. Give it a try.

[rickinnj]

If I want to, hypothetically, install a vacuum gage, do I just tee off of the scavenger tube?

[joe_db]

If I want to, hypothetically, install a vacuum gage, do I just tee off of the scavenger tube?

Yes - at the manifold, not the carb end.

[rickinnj]

I’m at the boat now. I reinstalled the exhaust last night so I can run the engine for vacuum troubleshooting.

This morning I pulled the carb to look for the Stevedore destructor at the urging of Indigo and others. No orifice plate.

While I have the carb out, I installed an adjustable main jet. Now the carb won’t go back in because the tee handle on the main jet hits the Facet pump before the carb flange lines up.

Gonna put the stock main jet back in and move on for now.

I’m at Tolchester if anyone wants beer or rum and a show.

[rickinnj]

Although not ideal, I hooked up a pressure gage to the discharge of the Facet pump and energized it…5#. A little high, but it’s not tee’d in with the carb hooked up. I’m gonna call fuel pressure good.

[joe_db]

Although not ideal, I hooked up a pressure gage to the discharge of the Facet pump and energized it…5#. A little high, but it’s not tee’d in with the carb hooked up. I’m gonna call fuel pressure good.

The A4 is very tolerant of fuel pressure. IMHO 3-5 PSI is just fine. Ever since I did the vapor return mine sits right on 4 at all times.

[Dave Neptune]

OK, now you have confirmed fuel delivery lets look to the ignition. I see that you stated the C-advance is smooth and lubricated ~ good.

Just for the sake of argument be sure the plug wires are in the correct order so it can be eliminated.

Now to the "spark", is it a "snappy blue" or an anemic and yellowish? If yellowish lets look at the coil and points if so equipped. If you have points "what is the dwell"(?), not what is the point gap? It is likely that the "cam" inside the distributor is badly worn by now so setting points with a dwell meter is a must for a good tune. The need of having to purchase dwell meter or purchasing an EI to replace ever needing to check dwell is a great option.

Also have you tried advancing the timing a few degrees to see if it helps. I'm guessing with the 3 blade a good running A-4 should see at least 17~1800 RPM's, not nearly enough to make much more than about 16~18 HP of the rated 25 HP.

Dave Neptune

[rickinnj]

Ok.
In neutral @800rpm: vacuum is running about 13inHg (oscillating wildly between 10 and 17inHg)

On snap accel/decel: bogs down to 1inHg and snaps back to 19inHg then settles back at previously mentioned idle numbers.

On gradual acceleration: vacuum lowers to 10inHg and is relatively steady.

[rickinnj]

Under load:

Forward full throttle is 980rpm and steady 2 inHg .
Astern full throttle is 1125 rpm and a steady 2inHg.