A lot is coming together since re-powering my boat with a 1977 55hp. I have determined that a bad setting on my tach and under pitched prop has caused my lack of speed and overall disappointment with the re-power.
I checked my tach this weekend and it was set to 6, which would be the correct setting for my original '97 50. I randomly tried another few settings, but they showed it idling around 4 grand and whatnot... obviously wrong. @ 6 is shows me idling around 1000 and WOT ~5100.
When I repowered with the rebuilt '77 55hp I didn't change the setting on the tach, and was disappointed with the purchase bc it would barely rev over 5 grand with the thirteen pitch prop. max speed was low 20's. With the '97 50hp motor i could rev 5600 with a 17 P prop, and move close to thirty MPH.
From what I understand the '77 is a 10 point, 5 pulse system, meaning that the true RPM's would be equal to (6/5)*(tach reading). I am curious if anyone can confirm this for me!!
This would put me over 6000 RPM WOT, and at risk of blowing the thing up!!!
I am using a thirteen pitch prop I bought for wakeboarding, because i trashed the original 17P on an oyster bar.
I felt that if I can barley turn 5 grand with a thirteen pitch prop moving up in pitch would be over proping. Now, based on my math, I need to reprop because I am currently overreving the motor.
Does all this make sense? I can't get to the lake till the weekend and would like to get a replacement prop ordered today. I think a 17 P is in order, as operating range is 5-6 grand, and currently I am turning (6/5)*(5000)=6000 RPMs (If my formula is correct)
I'd appriciate any input... I've been trying to get this right ever since the re-power last summer
I checked my tach this weekend and it was set to 6, which would be the correct setting for my original '97 50. I randomly tried another few settings, but they showed it idling around 4 grand and whatnot... obviously wrong. @ 6 is shows me idling around 1000 and WOT ~5100.
When I repowered with the rebuilt '77 55hp I didn't change the setting on the tach, and was disappointed with the purchase bc it would barely rev over 5 grand with the thirteen pitch prop. max speed was low 20's. With the '97 50hp motor i could rev 5600 with a 17 P prop, and move close to thirty MPH.
From what I understand the '77 is a 10 point, 5 pulse system, meaning that the true RPM's would be equal to (6/5)*(tach reading). I am curious if anyone can confirm this for me!!
This would put me over 6000 RPM WOT, and at risk of blowing the thing up!!!
I am using a thirteen pitch prop I bought for wakeboarding, because i trashed the original 17P on an oyster bar.
I felt that if I can barley turn 5 grand with a thirteen pitch prop moving up in pitch would be over proping. Now, based on my math, I need to reprop because I am currently overreving the motor.
Does all this make sense? I can't get to the lake till the weekend and would like to get a replacement prop ordered today. I think a 17 P is in order, as operating range is 5-6 grand, and currently I am turning (6/5)*(5000)=6000 RPMs (If my formula is correct)
I'd appriciate any input... I've been trying to get this right ever since the re-power last summer