Home › Forum › Ask A Member › ’57 Golden Javelin – fuel consumption question
- This topic has 30 replies, 11 voices, and was last updated 5 years, 9 months ago by
outbdnut2.
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June 29, 2018 at 3:55 am #78653
Anonymous
Good point on the trim pin. Adjust pin so that the cavitation plate is parallel to the bottom of the boat. Then add ballast to the boat in the front or rear to make the boat run level as needed,or with the bow lightened and just on the edge of porpoising. Michigan Wheel prop 10 1/2 x 11 #SMC52 is bronze or a #SMC53 three blade aluminum. Or a #AMC464 10×11 4 blade bronze. Or #012027 10 1/2 x 10 The first three are vintage props available used. The last would be new, but may be too low a pitch. you really need to test your current prop with a tachometer to figure out the best option with out buying more props to find out.
June 29, 2018 at 12:23 pm #78665cavitation plate is parallel to the bottom of the boat right now; tank & batteries are in the back. The boat gets up & moves pretty good, but a stronger holeshot might be nice for skiing.
June 29, 2018 at 5:42 pm #78676Anonymous
Then I would try a SMC52 or SMC53 first.
June 29, 2018 at 7:45 pm #78685Thanks. I made an offer on a SMC52 on eBay & I’m waiting to see if the seller accepts. There’s a limit to what I’ll spend on a used prop…
EDIT: Won the auction! SMC52 on it’s way to me….
So now I have a 13-1/2 that the engine didn’t like at all pushing this boat, a 12" that seemed OK this past weekend, and an 11" on the way. Game on!
Digging through the garage, I found another prop that "fits", but has no markings on it. I’ll set up my measuring rig tomorrow & see. Hopefully it’s not an 11" since I just bought one!
June 30, 2018 at 1:05 am #78700Anonymous
Good luck
June 30, 2018 at 2:30 am #78713quote NJ-boatbuilder57:cavitation plate is parallel to the bottom of the boat right now; tank & batteries are in the back. The boat gets up & moves pretty good, but a stronger holeshot might be nice for skiing.When you pull skiers, try dropping the trim pin down one notch – it’s like shifting to a lower gear! You will be surprised at the difference in the hole shot, but may not have enough top end left for heavy skiers and as mileage will suffer. On Dad’s old 1960 40 HP, I dropped the pin one notch when I pulled triple teenage skiers or couldn’t get a heavy skier out of the water.
DaveJune 30, 2018 at 2:32 am #78714quote outbdnut2:quote NJ-boatbuilder57:cavitation plate is parallel to the bottom of the boat right now; tank & batteries are in the back. The boat gets up & moves pretty good, but a stronger holeshot might be nice for skiing.When you pull skiers, try dropping the trim pin down one notch – it’s like shifting to a lower gear! You will be surprised at the difference in the hole shot, but may not have enough top end left for heavy skiers and as mileage will suffer. On Dad’s old 1960 40 HP, I dropped the pin one notch when I pulled triple teenage skiers or couldn’t get a heavy skier out of the water. That’s why most newer motors of any size have power trim buttons for the driver. Of course with power trim, you can raise the trim back up once you have the skier out of the water.
DaveJuly 6, 2018 at 2:48 pm #79114So the SMC52 showed up last night….nice prop in great shape! I’m looking forward to trying it out.
Driving to work this morning, I got to thinking: Yes, I want to get a TinyTach so I can best "dial in" my engine / props / boat, but as I plan to do so, it makes me wonder. TinyTach is a very new invention (with respect to these old engines). Back in the day (I’m talking outboards, pre-dashboard tachs), the guy at the marina clamped the engine to the transom and said "have fun" as we went on our boating way. We neither knew about…or cared about…RPM@WOT. The HP@RPM plaque on the engine meant something to someone, but I suspect it was pretty meaningless to most recreational boaters. I know it was meaningless to me. Some boats ran better than others, and that was pretty much the end of it.
Yes, I understand the consequences of under-or-overloading the engine, and I’m by no means poo-pooing what technology can do for us today, but I can’t help but wonder: for the history of boating in the ’50s – ’60s, did anyone know HP@RPM@WOT? Did anyone care? How was RPM even determined in the absence of a tank & a dyno? Strobe light? Certainly not something 99% of recreational boaters knew anything about…
Are we chasing the perfection point to a decimal that really doesn’t matter just because we can? Are we obsessing when we should be having fun?
Don’t misread: I’m not looking for a "pass" from getting my boat/engine/prop tuned in as best as we can, and with the tools to do so being as inexpensive as they are, I’m looking forward to it. But it still makes me wonder….are we chasing something that needn’t be chased? Would our time be better spent "boating" rather than "tweaking"? I’m not sure.
Either way, it’s a fun journey!
July 6, 2018 at 3:29 pm #79116Tachometers existed way before 1957. Mercotronic even sold portable service tachs. A tach is useful for setting up your boat. Once you know what the best prop is for your boat the tach is no longer that important. Most people have no idea if their prop is the correct pitch. As long as it turns they are happy.
Wayne
Upper Canada Chapteruccaomci.com
July 6, 2018 at 3:45 pm #79117I guess the matter of optimizing propeller selection, motor tilt, and motor height could be more or less dismissed as long as the boat runs, but motors are designed to run at a certain RPM range at full throttle: too low, and the motor doesn’t make the power (especially true with two-strokes) and too high, the motor’s internals are stressed beyond design limits. There may also be a fall-off of power, but it depends on induction and exhaust tuning.
The limiting factor in smaller and older motors is that the selection of propellers is usually small. That said, in the heyday of Michigan Propellers there was a pretty wide selection, which suggests that yes, many people did measure RPM and speed with propeller changes.
Owners of larger, more powerful boats pay close attention to propeller selection, to the extent that every combination is well tested.
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