I took my first trip that I had to motor & motor sail any distance. 15 hours 15 gal. This was doing about 6 kn and 1800 to 2000 rpm. This is not what I expected for fuel economy. What are other owners with the M35b getting?
The bottom is clean, the conditions were moderate, and I have a 3 blade Max-prop set at 10 inches per rev. The engine appears to run good and has 590 hours. I do have some soot around the exhaust but I don't see much smoke.
Should I have the injectors checked?
I've kept an eye on fuel consumption since I took possession of Breezing Up (#1471) in 2000. I have the same engine, the M35B. I have the standard Catalina fixed two-blade prop, and I use about .6 to .65 gallons per hour at cruising RPM (2300 or so). That number has held up pretty consistently. When my hull, prop, and prop shaft are clean I do about 6 to 6.5 knots at that RPM.
I'm impressed that you can do 6 knots at those RPMs you mentioned. Maybe I should switch props....
I'm not a diesel engineer, but I have two thoughts: checking the injectors makes sense, and I'm mildly suspicious of your tachometer readings.
Good luck!
George Alberts
I have the smaller M25XP, so it's not directly comparable, but for what it's worth I cruise at 2100-2200 rpm and burn a little more than 1/2 gallon per hour at 6 1/4 knots.
Some earlier input from skippers: http://c34.org/bbs/index.php/topic,3824.0.html
Jim,
I burn roughly .8-.9 gal at 2000 RPMs that gives me about 5.8-6.2 knots depending on sea state. I have a 10 inch Kiwi 3-blade feathering set at 17.5 degrees (which is about 10 inches pitch).
I just cleanded my injectors this spring along with the tank and installed a new tank sensor. My tach is accurate as I check it against a digital tach yearly.
Steve
In reading the other postings, I'm thinking my fuel efficiency number is a bit off. I don't consistently run the engine at 2300 rpm--if I can do so and maintain a decent speed over ground, I drop it to 2000-2100. According to my log, I am indeed using a bit than .6 gallons per hour, but not quite .7 gallons per hour. But if I ran at 2300 all the time it would probably be in the .8-1.0 gallons per hour, especially in anything but calm or moderate seas.
if you are getting soot it sounds like you might be a bit over pitched. That will also hurt your fuel ecomomy. Might try a search on Max prop and see what others are running
Jim, My M35A with Autoprop burned .85 gph at 2000 rpm on the same trip we both made from Ashtabula to Erie, Pa on Wednesday. . I was towing a dinghy, which kept my speed down to 6 kts. On flat water I will go 6.4 kts at 2000 rpm without the dinghy. . At 2200 rpm, I achieve 7 kts and 7.3 kts at 2500 rpm. The sweet spot for me is 1900 rpm at 6+ kts and 0.7 gph. When I motor sail, my fuel consumption drops tp 0.5-0.56 gph at 1500-1700 rpm.
Jack F Stewart
1993 C36 #1233 "Windancer"
Port Clinton, OH
Now at Wolverine Marina in Erie, Pa. Leaving for Port Dover, Ca on Sunday
Guys, Susan and D. Gill : Fuel consumption is a tough parameter to zero in on!! The previous responce is from a C36 (differant wetted surface area, differant prop and a M35A 30hp engine)
My original M25XPA when it was new was about .46g/h. In it's later life went up to .5g/h. My new M25XPB is .56g/h. Same prop (3 bladed fixed Sailor) - same RPM.
I'll guess that M35XPB is going to be about .75 - in a C34. A thought
Desiree, C34 Mk II, #1472: M35B engine w/fcty installed 3 Blade Fixed Prop.
In 2008, 300+ miles trip resulted in 0.6 -.66 GPH @ 2000-2100 over a wide variety of sea and current conditions. Hope it helps.
Mariah lll C34 Mll # 1555, M35B with factory 3 blade. Average .75-.8 at 2500 rpm towing my 50# hard dingy.
Jack
Cat 34 MKII Hull 1760, M35B factory 3 blade fixed prop.
2200 RPM....... .6-.7 gal. 6.6 knots
2400 RPM....... .7-.8 gal. 6.9 knots
2600 RPM....... .8-.9 gal. 7.2 knots
Add .1-.2 in chop or waves over 2-3 feet.