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  #1   IP: 207.32.171.10
Old 08-19-2021, 02:31 PM
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suddenly magical fuel economy

Last year (2020) I installed a new digital hour meter, the Isspro R8865 from Moyer. It replaced the old mechanical hour meter, part of the ancient mechanical tachometer that runs off the accessory drive. After decades of running well it stopped turning over the hours and started clicking. The little plastic worm drive finally gave up the ghost. I didn't realize until I took it apart that I was supposed to oil it. There was a tiny cup on the back to drop oil into. The tachometer still works. It took me a while to realize I was now counting the hours the ignition was on, not the hours the engine had been running. I try to not leave the ignition on, but occasionally it happens, sometimes overnight. I know this is supposed to fry the coil, but I have seen no evidence of that. The coil I have now was bought from Moyer in 2018.
Anyway, since the new hour meter my fuel economy has improved about 100%. I used to average about a gallon an hour, now it is two gallons an hour. I have put 75.6 gal in the tank to fill in 4 fill-ups, while the new hour meter has elapsed 172.3 hours. That's 2.28 hours per gallon. I do spend a lot of time in forward at low rpms, maybe that's it, but that's nothing new. Unless I have been leaving the ignition on with the engine off as much as when it's running, which I doubt, I have no explanation for this phenomenon. The good old A4 is running like a champ; starts easily with choke, a little rough until it warms up in a few minutes. I have an Indigo thermostat which warms it up quickly. The idle adjustment screw is out from the seat 1 turn, adjustable main jet is out 2 turns. It may be a little rich, but I see no soot on the plugs. No smoke in the exhaust. I have put 3000 hours on the beast since the rebuild in 2001. I did retard the timing a bit this spring (turning distributor counter clockwise) while running at 1500 rpm in forward, to make it sound better. in 2019 the vacuum at 1500 rpm was 10, now it is 12, so the engine isn't working as hard. I get about 5.5 knots at 1750 rpm. Is it possible that a slight timing adjustment could decrease fuel usage by a factor of 2?
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  #2   IP: 134.41.132.177
Old 08-19-2021, 05:33 PM
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I find it depends. I don't use a T-stat but have been running a hotter top end for years. 1/2 gallon an hour is normal in calm waters. Prop dimensions, clean bottom, boat design and fuel grade all make a difference. I started out my 450 NM trip with high octane fuel but when I filled up all that was available was the regular...does it make a difference? You bet. I found my fuel consumption changed when i couldnt choose my grade of fuel. Dont get me wrong, there was no water or anything in it, it just doesn't produce the same power which results in higher fuel consumption.

If we are not running the engine in trying conditions it doesn't matter....if I scooted down a calm inlet or waterway you bet my fuel economy will be good and hang in about 1/2 gallon per hour. Put it to the test in 3 or 4 meter seas for hours on end an see where it is? I'm pretty close to a gallon an hour (.89 gallons an hour) running hard into it, but I think I'm tuned in pretty good. Hours and exact amount of fuel don't lie. It was even easier for me filling my boat tank every night...I knew the conditions I'd just been through and got a good idea what it burned in which conditions.

My last post on my fuel economy was mostly ocean. To put that trip in perspective we spent 7 days, including both directions in at least 6 foot sea. A 10 hour day in 3 meter seas, and about 3 hours on another day in 4 meter seas. The days we were caught in seas was because idiots in out weather station didn't work...no doubt in my mind. I'd posted prior to that the hour and fuel usage in the hbr....an easy 1/2 gallon per hour with no sails up in harbour conditons. With all said and done there are lots of variables on individual boats that affect fuel consumption. I'm sure if I'd kept the boat lighter it would have been better, however, when seas got rough the C&C 30 kept going when others ran for cover. I had lots of weight aboard.

Approaching my 2000 nautical miles for this year...if all goes well I'll be closer to 3000...been trying to sneek in sails everywhere I can.
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The pessimist complains about the wind.
The optimist expects it to change.
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Last edited by Mo; 08-19-2021 at 05:37 PM.
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Old 08-19-2021, 08:42 PM
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Quote:
Originally Posted by capnward View Post
I did retard the timing a bit this spring (turning distributor counter clockwise) while running at 1500 rpm in forward, to make it sound better.
Point of technical accuracy: rotating the distributor body counter clockwise actually advances the timing.
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prior boats 1987 Westsail 32, 1970 Catalina 22
Had my hands in a few others
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Old 08-21-2021, 11:07 AM
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My thought is that that worm gear didn't wear out all at once. It probably started slipping, one tooth at a time, until gradually it got worse and worse and finally stopped. The slipping would have recorded fewer hours than actual, resulting in an artificially increased gallons per hour. Once you replaced the hour meter, you went abruptly back to "real time", producing a noticeable "decrease" in gallons per hour.
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  #5   IP: 207.32.171.10
Old 08-22-2021, 02:31 AM
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Thanks for that thought, Ed. I would like to think that my A4 gets similar fuel economy to a diesel. The problem with that scenario is that for years I have been estimating how much gas would fill the tank based on the hours elapsed on the old hour meter, and always been close to the estimate. I would estimate 1 gal/hour, and behold, that's what would fill the tank. The old hour meter seemed to work perfectly until it didn't work at all. But it could very well be that the hour meter was skipping gear teeth the whole 25 years I had it, since I never oiled it. This now seems like the plausible story. For the first few fill-ups since the hour meter replacement, I continued to estimate 1 hour per gallon, but to my surprise half that many gallons filled the tank. It just occurred to me that I should check the new hour meter against an actual clock when running. It registers in tenths of an hour, so that should be easy. It may also be that I have been running at lower rpm than before and not realizing it. I will spend more time at cruising speed and see if that makes any difference. Most all of my motoring is in easy conditions, as I am in the middle of an archipelago in the calmer time of year.
Oh wow. It just occurred to me that if my old hour meter had been counting hours at half speed for 25 years, I actually have put 6000 hours on the engine since the rebuild in 2001, not 3000. Huzzah for the durable A4!

Last edited by capnward; 08-22-2021 at 02:53 AM. Reason: epiphany
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Old 08-22-2021, 08:06 AM
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I planned a 2 week vacation on the boat this year and I knew I had to tackle the Eastern Shore of NS to Bra Dor Lakes. Late August into September that is a decent coast to explore, but May, June and July will inevitably lean towards an uncomfortable to miserable stretch of water. There are few services along that route and even getting gas can be a bit of a chore, so I spent some time previous to leaving measuring exactly what I was using for fuel. The Bra Dor Lakes are just a paradise to sail and in the end the misery getting there AND back was worth it.

I averaged .65 gallons per hour and it was all ocean running in swell. As mentioned, I got into a couple of blows where it burned .89 gallons per hour. I was travelling alone (sole boat by wife and son aboard) although I did meet people along the way, some who left earlier and were holding fast in areas waiting for better weather that wasn't coming.

Talked to a few of them and guys with 2GM Yanmars that figured their fuel usage was burning just over a litre (pretty much a quart) an hour (Diesel). I have a friend with a C&C Landfall 38 that burns about 1/2 a gallon and hour of diesel but he can probably scoot along at 7 or 8 knts with that.

On the Friday that I left to come back from Bra Dor Lakes three of us made it out through the St Peter Canal locks with a forecast of good weather. Before crossing Chetabucto Bay were into a blow and the two behind me couldn't keep way on...they were being stopped dead in the water by the increasing waves. Once boat Irwin 32, the other C&C 29 both with Yanmar 2GM's. Initially we were able to sail with no engines and then dark clouds and rain could be seen downwind of us on the land....that whole thing rolled over us with a major wind shift and increase. We all went to engine and main-sail, furling the jibs and drove into it.

The area we were in has lots of shoals, and to run to Canso meant I had to cross many of them. I was able to keep the boat moving but the engine was working hard. Those two boats behind me couldn't keep way on and took the chance of going to Canso. I didn't want to do that because the waves coming in over the shoals there would likely be more problematic than the 3 meter rolling seas that were building up on the nose. I knew I had a good boat, good engine, good rig and experience so the safest thing for me was to keep going and make it to Yankee Harbour. I think it took me 8 hours from the time we left the canal so about 5 or 6 hours of that was in pretty heavy stuff. This is one of the times the old girl sucked fuel, however, the lower HP diesels couldn't face it just driving through it on the nose. I'm sure they could have veered off and motor sailed but that would add hours to their trip. So their call on that one was probably a good one.

I'd carried 4 Jerry Cans of fuel and topped up every night so knew what I was using, writing down the hours. IT WAS a great feeling to know I had 20 gallons of fuel in the tank and would have no problem with supply to do the leg of the trip I was doing. So much worry off, when so much going on and was so happy I took the effort to see exactly what my fuel usage was for that trip.
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"Odyssey"
1976 C&C 30 MKI

The pessimist complains about the wind.
The optimist expects it to change.
The realist adjusts the sails.
...Sir William Arthur Ward.

Last edited by Mo; 08-22-2021 at 07:50 PM.
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