Montauk 17 with 115-HP 25-inch-shaft
Posted: Tue Apr 13, 2021 10:18 pm
Hi all. I own a 1999 Montauk 17. In 2020 I re-powered a Yamaha 115-HP 25-inch-shaft two-stroke-power-cycle engine in near-mint condition that is older than the the 22-year-old MONTAUK. The engine is mounted on a no-set-back T-H Marine 50012 CmC 5-inch Vertical Extension. The propeller is a standard, original, aluminum Yamaha propeller, marked 17K ( I believe).
The boat pops up on plane very quickly and will do you about 45 at wide open-throttle. I cannot run it at open throttle though as the engine will quickly exceed the 5,500-RPM redline. I'm assuming lots of SLIP and deformation of the soft aluminum propeller. I know there's a lot more speed in it, but that's not necessarily my question.
The question is related to the problem that hat the propeller blows out [ventilates] when taking even a slightly aggressive turn. Currently, when on plane, the anti-ventilation plate skims right at water level, which I believe is perfect. I'm assuming the old generic aluminum propeller [is causing the blow-out], which leads me to my question:
How in the world do I figure out what the best-all-round propeller is for my set up?
I'm sure with the proper propeller, the ventilation in corners will end and I'll pick up efficiency and perhaps a few more miles an hour.
I hear and read all the time about people testing different propellers, but for the life of me, I can't find somebody that's going to share stainless steel props with me to play with.
So I'm hoping the pros out there can lend a hand.
Give me a place to start.
I'd like to stick with a three blade stainless steel propeller, but I'm not against a four-blade stainless steel propeller. The ideal propeller would yield 5,500 PRM with a 600-lbs load. That might mean 5,800 RPMs with a light load, but I can modulate.
Please ask me anything that will help you (and help me) to mate the right propeller to the engine. I promise to capture and share the adventure.
Thanks for reading, Ed
BACK STORY: For 21-years great years the 1999 MONTAUK 27 was powered by a three-cylinder Yamaha 90. That engine was so good for so long, but it finally suffered corrosion in its water passages. There was no repair without disassembly, cleaning and, of course, extracting and tapping all of the bolts that snapped.
I really like the old-schoolYamaha 115 engine. It has no automatic fuel-oil mixing so you must pre-mix the fuel and oil in the fuel tank at 50:1 ratio. Mixing the fuel with oil in the fuel tank (in lieu of "Precision blend") is simple, slightly lighter weight, and--perhaps oddly--very satisfying as it helps to condense the evaporation of time. I love this engine, and it runs like a gem.
Subjectively, the boat looks admirable by eye with the extension. On top of that, the extra space between the motor and the engine splash well renders the splash well much more useful. But enough about that.
ASIDE: I can't believe this is the first time I've posted on the new forum. I participated on the old site for many many moons (with username ewalsh). I want to say I joined in 2001. How time evaporates right in front of you.
The boat pops up on plane very quickly and will do you about 45 at wide open-throttle. I cannot run it at open throttle though as the engine will quickly exceed the 5,500-RPM redline. I'm assuming lots of SLIP and deformation of the soft aluminum propeller. I know there's a lot more speed in it, but that's not necessarily my question.
The question is related to the problem that hat the propeller blows out [ventilates] when taking even a slightly aggressive turn. Currently, when on plane, the anti-ventilation plate skims right at water level, which I believe is perfect. I'm assuming the old generic aluminum propeller [is causing the blow-out], which leads me to my question:
How in the world do I figure out what the best-all-round propeller is for my set up?
I'm sure with the proper propeller, the ventilation in corners will end and I'll pick up efficiency and perhaps a few more miles an hour.
I hear and read all the time about people testing different propellers, but for the life of me, I can't find somebody that's going to share stainless steel props with me to play with.
So I'm hoping the pros out there can lend a hand.
Give me a place to start.
I'd like to stick with a three blade stainless steel propeller, but I'm not against a four-blade stainless steel propeller. The ideal propeller would yield 5,500 PRM with a 600-lbs load. That might mean 5,800 RPMs with a light load, but I can modulate.
Please ask me anything that will help you (and help me) to mate the right propeller to the engine. I promise to capture and share the adventure.
Thanks for reading, Ed
BACK STORY: For 21-years great years the 1999 MONTAUK 27 was powered by a three-cylinder Yamaha 90. That engine was so good for so long, but it finally suffered corrosion in its water passages. There was no repair without disassembly, cleaning and, of course, extracting and tapping all of the bolts that snapped.
I really like the old-schoolYamaha 115 engine. It has no automatic fuel-oil mixing so you must pre-mix the fuel and oil in the fuel tank at 50:1 ratio. Mixing the fuel with oil in the fuel tank (in lieu of "Precision blend") is simple, slightly lighter weight, and--perhaps oddly--very satisfying as it helps to condense the evaporation of time. I love this engine, and it runs like a gem.
Subjectively, the boat looks admirable by eye with the extension. On top of that, the extra space between the motor and the engine splash well renders the splash well much more useful. But enough about that.
ASIDE: I can't believe this is the first time I've posted on the new forum. I participated on the old site for many many moons (with username ewalsh). I want to say I joined in 2001. How time evaporates right in front of you.