Post by mudbug on Aug 30, 2020 10:03:48 GMT -5
On my '99 198 DC with a '99 115 Yamaha, I'm slow to plane and only reach max RPM's of 4100. My current prop is a 13.25 x 19.
My top speed is 40 MPH, which I enjoy, but getting there is a struggle and I want to do what's best for my boat and motor. I struggle to reach plane and once there, I lose plane easily as well. I use tilt/trim to help with this, but when I realized that at maximum speed, I'm only reaching 4,100 RPM's, I know I need to stop lugging my motor.
From what I'm reading, in order to get my RPM's up to 4,500, I can go to a pitch of 17, but that will only get my RPM's up to 4,500. Is that enough of a change? The boat was recently serviced including compression check, new plugs, water pump, foot grease change, thermostats replaced, timing and carb sync adjusted, and other stuff that I can't remember. Motor fires right up and runs great. Is running at 4,500 RPM's good enough, or should I be more in the middle of the 4,500 - 5,500 RPM range for my motor? If so, do I change to a smaller diameter prop as well as a lower pitch? Again, I'm not as interested in speed as doing what will make my motor "happy" and enable it to last forever!
Thanks in advance for the help!
Also, when setting up a boat, I've always placed the motor where the cavitation fin is even with the lowest point of the "V" of the hull. On my Sailfish boat, the hull has a step at the very back. The cavitation fin on the motor does not reach the bottom of the "V" in the hull but is somewhere between the "V" and the flat "step" area all the way at the back of the hull. Is my motor sitting too high? I hope not because that would require a longer motor. Also, the boat and motor are both original from the manufacturer and I'm sure they know what they're doing when they pair the boat to the motor, so I assume that this mounting is correct. I do have some cavitation problems with very little trimming. This may be due to all my passengers preferring to sit in the bow area when I have passengers.
My top speed is 40 MPH, which I enjoy, but getting there is a struggle and I want to do what's best for my boat and motor. I struggle to reach plane and once there, I lose plane easily as well. I use tilt/trim to help with this, but when I realized that at maximum speed, I'm only reaching 4,100 RPM's, I know I need to stop lugging my motor.
From what I'm reading, in order to get my RPM's up to 4,500, I can go to a pitch of 17, but that will only get my RPM's up to 4,500. Is that enough of a change? The boat was recently serviced including compression check, new plugs, water pump, foot grease change, thermostats replaced, timing and carb sync adjusted, and other stuff that I can't remember. Motor fires right up and runs great. Is running at 4,500 RPM's good enough, or should I be more in the middle of the 4,500 - 5,500 RPM range for my motor? If so, do I change to a smaller diameter prop as well as a lower pitch? Again, I'm not as interested in speed as doing what will make my motor "happy" and enable it to last forever!
Thanks in advance for the help!
Also, when setting up a boat, I've always placed the motor where the cavitation fin is even with the lowest point of the "V" of the hull. On my Sailfish boat, the hull has a step at the very back. The cavitation fin on the motor does not reach the bottom of the "V" in the hull but is somewhere between the "V" and the flat "step" area all the way at the back of the hull. Is my motor sitting too high? I hope not because that would require a longer motor. Also, the boat and motor are both original from the manufacturer and I'm sure they know what they're doing when they pair the boat to the motor, so I assume that this mounting is correct. I do have some cavitation problems with very little trimming. This may be due to all my passengers preferring to sit in the bow area when I have passengers.