AEROCOOK
Master Chief Petty Officer
- Joined
- Jul 28, 2004
- Messages
- 872
[FONT="]I'm helping a friend try to figure out a problem with his boat and frankly, we're stumped.
The boat is a 16' Legend aluminum fishing boat and the motor is a 1997 Mariner 40hp 4cyl. Last year he hit a rock at high speed which destroyed the lower unit, he took it to a mechanic who installed a used lower unit, and that's when the problem began. The motor runs very well and will reach 5500 rpms quite quickly but the boat is going very slowly and wont plane. At one point in our test run, the rpms spiked up to around 6500 and the boat actually slowed, kind of like a spun hub would do. I confirmed that the gear ratio of the replacement LU is the same as the original one, tried 2 other props with different pitch but the problem persists. Also, we made sure the boat wasn't water logged. What else is there to check? [/FONT]
The boat is a 16' Legend aluminum fishing boat and the motor is a 1997 Mariner 40hp 4cyl. Last year he hit a rock at high speed which destroyed the lower unit, he took it to a mechanic who installed a used lower unit, and that's when the problem began. The motor runs very well and will reach 5500 rpms quite quickly but the boat is going very slowly and wont plane. At one point in our test run, the rpms spiked up to around 6500 and the boat actually slowed, kind of like a spun hub would do. I confirmed that the gear ratio of the replacement LU is the same as the original one, tried 2 other props with different pitch but the problem persists. Also, we made sure the boat wasn't water logged. What else is there to check? [/FONT]