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  #1   IP: 24.61.231.173
Old 10-06-2013, 03:51 PM
richardcmarsh richardcmarsh is offline
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Rebuild does not deliver power of original A4

Two years ago I bought a re-built A4 from Moyer Marine. Engine runs well, but never exceeds 1700 RPM under load and the boat (1981 Catalina 30) never exceeds 5.0 knots in the water. The old A4 would go to at least 2000 RPM (though I rarely exceeded 1800) and would move the boat at 6.0 knots. Same propeller, clean bottom, exhaust hose replaced this past winter. It was 5 kts/1700 rpm from the day it was put into service mid season after crankshaft died on old A4. The hull speed calculation for a boat with 25' waterline is 6.5 kts. Any thoughts?
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Old 10-06-2013, 06:41 PM
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Have your checked compression?

Are you sure you are getting spark to all four cylinders?

I have no doubt the MMI will make it right.

I bought a rebuilt MMI years back for my C&C 34. After a couple of hours, I heard some kind of knocking. It ran well, but the sound bothered me. I called Don. He asked me to pull it, bring it back. His guys tore it down, checked all the specs, put it back together, no charge. I put her back in, sound was gone. So, I don't know what changed, neither did they, but it worked. Pushed her to nearly 7 kts. Good temp and pressure.

Currently, my 1966 vintage A4 can push my Tartan 27 to 6 kts. It has 100 lbs compression in each, runs at 160 degrees, 40 lbs pressure.

So, if the very wise people on this site don't help you find a solution, call Don.

Good luck.

Chris
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  #3   IP: 174.94.32.10
Old 10-06-2013, 09:01 PM
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67c&ccorv 67c&ccorv is offline
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How did the marrying up of the direct drive coupling with the prop shaft go?

What prop are you running?

Did the rebuild include new carb and fuel pump?


Last edited by 67c&ccorv; 10-06-2013 at 09:03 PM.
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Old 10-06-2013, 09:42 PM
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Marian Claire Marian Claire is offline
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Welcome to the forum. What RPM do you reach in neutral? One thing that has to be changed during an engine swap is the throttle linkage connection. Being as this was an instant change I wonder if the linkage is problem.
Interesting.
Dan S/V Marian Claire
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Old 10-06-2013, 10:04 PM
richardcmarsh richardcmarsh is offline
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Thanks for thoughtful responses. Carb and fuel pump are relatively new. I cleaned and reassembled carb this spring. Pump delivers plenty of fuel. Same prop which is standard, I think 12 x 9. There is no vibration in shaft. I think the lingo is a "short block swap" done within a month - nothing but the block was changed. I have tried manually controlling the throttle and have adjusted the cable. It revs close to 3000 in neutral if I am not careful. All plugs are dry. I have not checked compression.

I am constantly promoting Moyer Marine after nearly 20 years acquaintance.
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Old 10-06-2013, 10:14 PM
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Quote:
Originally Posted by richardcmarsh View Post
Thanks for thoughtful responses. Carb and fuel pump are relatively new. I cleaned and reassembled carb this spring. Pump delivers plenty of fuel. Same prop which is standard, I think 12 x 9. There is no vibration in shaft. I think the lingo is a "short block swap" done within a month - nothing but the block was changed. I have tried manually controlling the throttle and have adjusted the cable. It revs close to 3000 in neutral if I am not careful. All plugs are dry. I have not checked compression.

I am constantly promoting Moyer Marine after nearly 20 years acquaintance.
Compression check would be a good start. I find 6.2 is the fastest I can get my C&C 30 going is calm water with a clean bottom. Prop cleanliness and condition of the bottom of the boat mean so much as well.

Good luck.
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  #7   IP: 24.152.131.153
Old 10-06-2013, 11:24 PM
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The 9 inch pitch on your 12 inch prop is awfully aggressive. For a 12 inch prop you'd be happier around 6 or 7 inches on the pitch. The A-4 powered Catalina 30 (thousands of them?) had a 12x7 prop.

I believe those who like the Indigo prop do so because of the performance difference with a reduced diameter (10") and 7.7" pitch more than the winglet concept. In fact, Indigo discusses just that in their product description (interesting how their numbers mirror yours):
Quote:
The vast majority of Direct Drive Atomic 4 yachts were originally equipped with a 2 blade, 12" diameter by about 9" pitch propeller. This application allows the vessel to achieve a respectable cruise speed in calm waters at about 1400 RPM. However, wide open throttle is only about 1700 RPM which leaves very little reserve for foul weather or bottom fouling. Furthermore, at 1400 RPM, the engine is working very hard (near maximum cylinder pressure) which leads to high loads on rings, pistons, and bearings.
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Last edited by ndutton; 10-07-2013 at 12:48 AM.
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Old 10-07-2013, 12:00 AM
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67c&ccorv 67c&ccorv is offline
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Quote:
Originally Posted by ndutton View Post
I realize this does not address your question but the 9 inch pitch on your 12 inch prop is awfully aggressive. For a 12 inch prop you'd be happier around 6 or 7 inches on the pitch. The A-4 powered Catalina 30 (thousands of them?) had a 12x7 prop.

I believe those who like the Indigo prop do so because of the performance difference with a reduced diameter (10") and 7.7" pitch more than the winglet concept. In fact, Indigo discusses just that in their product description (interesting how their numbers mirror yours):
That's how it went when I changed the old two-blade "sailor prop" for an Indigo on my vessel Neil...1967 C&C Corvette.

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  #9   IP: 108.23.219.177
Old 10-07-2013, 09:14 AM
Dave Neptune Dave Neptune is online now
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Lightbulb Hmmm

Richard, the performance should be the same if all else is clean and the "same". As you did a short block, my first check would be the timing and the c-advance. Once confirmed fine I would look to the exhaust for a blockage. If it was about to plug up, it may now be plugged up enough to compromise performance.

Your prop does sound a bit aggressive for your boat as far as pitch is concerned.

Also you may want to check the tach wiries too.

Dave Neptune
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Old 10-07-2013, 09:59 AM
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My "new" A4, while a thousand times better in every way than the old one that had myriad issues, is a bit slower. The old one - when it was working right - could be roused to a bit more power until something went wrong with it. There is some variation between engines apparently. I would also agree that 12x9 should be switched for 12x7 or an Indigo. I can hit about 6.2-6.5 knots with a clean bottom with a 35 foot boat. With a clean prop I can hit 2300-2400 RPM.
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  #11   IP: 70.208.74.99
Old 10-07-2013, 11:45 AM
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I find it hard to believe that a rebuilt engine can categorically be said to have less power than the original. These engines never get close to their maximum output to begin with, and there are hundreds of variables associated with the process of removing and reinstalling an engine.

I would wager that in a controlled environment, carburetor settings, condition of prop/hull, engine alignment, and possibly deteriorating condition of unchanged components (like the exhaust system or fuel supply) would account for almost all of the perceived differences between new and old.
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Old 01-01-2015, 09:24 PM
richardcmarsh richardcmarsh is offline
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Compression

Compression - none in 4th cylinder. With coaching from Don, I replaced the aft most valve in March. Went on to have a great 2014 season. Since I never before had the full power I expected, it appears mechanic who installed the re-built engine must have had trouble starting it and backed up water into the engine. He did a few other really stupid things - like not connect the alternator. That was 7 or 8 years ago. The circumstances at the time did not permit me to do the work myself. Another reminder that it is best to do the work yourself if at all possible.
Thanks for all the forum suggestions - huge motivation.
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Old 01-02-2015, 03:27 AM
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Quote:
Originally Posted by Mo View Post
Compression check would be a good start. I find 6.2 is the fastest I can get my C&C 30 going is calm water with a clean bottom. Prop cleanliness and condition of the bottom of the boat mean so much as well.

Good luck.
My prop is 12/6 pitch. Michigan 3 blade. It does it for me. Once I leave the dock I have just over a mile and I'm on open ocean. I find the 3 blade prop good in chop sea and keeps the boat moving into it....something to consider if you are wondering if you should have a 2 or 3 blade.
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The pessimist complains about the wind.
The optimist expects it to change.
The realist adjusts the sails.
...Sir William Arthur Ward.
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  #14   IP: 70.24.14.31
Old 01-02-2015, 11:52 AM
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I am wondering. As it happens,I have my prop and new shaft and cutlass in my basement awaiting spring. I see the 12 in the prop measurement, but where does the 6-7-9 number come from and how do I tell which prop I have?
Thanks
Greg Cat 30 hull 696
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Old 01-02-2015, 12:14 PM
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Greg, The pitch should be stamped right after the 12 on the prop hub somewhere..Mine was on the end I think..With marine growth it can be hard to read..Sometimes you need to burnish the area for the stamping to show up.

C-30's of our vintage with Atomic 4s came with a 2-blade 12" diameter x 7" pitch prop.
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  #16   IP: 70.24.14.31
Old 01-02-2015, 07:42 PM
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Hey Shawn,
Thanks very much. Turns out to be a 12 X7. Was looking for shaft alignment posts this week. Read your Indigo thread over a couple days. Wow!
Reminded me of my own disaster in getting water out of the engine after a full knock down on my C 30 and the eventual rebuild last winter to chasing fuel problems this summer.
But in the end, the good guys on this site get you past the nervousness of maybe making a bigger mess.
Thanks
Greg c30 hull696
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Old 01-03-2015, 12:45 AM
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Full Knockdown

Greg, I think we are all in on your engine issues and sounds like they are almost all working right, but what can you share about the knockdown? Did a summer freak wind come on you? Main companionway wide open? I've been through some strong surprise gust winds out in the Gulf on C30 and she did well (quite an experience though). the worst knockdown damage we encountered was shearing the whole toilet seat off the head (not as easy to use afterwards by the way for the next 100 miles by six guys in the Harvest Moon Regatta). Point is, tell us about how the engine became flooded and what all you sustained and did to overcome and get back to port. What you share may help me in the future or someone else anyway.
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