Why would you switch drive ratio?
01-09-2023 | 07:12 PM
#11
Registered
Joined: Aug 2021
Posts: 112
Likes: 62
From: Hawaii
As I understand this. I’m currently toying with redoing my gear ratio.
it’s the Difference between torque and top speed
torque:
the higher ratio will produce torque. My bravo 3 is setup in 2.0:1. This helps the boat get on plane (faster and stay there at slower speeds). What it loses is top end speed. I’m seriously jealous of you 3digit guys. But my boat spends most of its life high speed trolling in rough water. 6-8’ is normal here.
Top speed:
but lower ratios like 1.5, 1.36 etc will allow much higher top end speed assuming it has enough torque to get on plane. Of course props factor into this equation etc. I have 20p and 22p duo props but I expect I’ll be propping all way out to 24-26p to compensate for my torque monster. And remember I’m on a dual prop which seem to be geared differently than normal single props. I wanted the boat to run straight when I need to leave helm to wrestle in a fish if I had no competent help on Baird. Trust me that struggle is real.
similar to truck towing axle ratios the higher the number more it can tow (torque) but lower top end speed and worse fuel economy.
this is my best understanding and many much more knowledgeable people on this board. But I’m starting to toy with this myself but I want to find the perfect setup now and then start making small changes before I get too radical (gear change).
it’s the Difference between torque and top speed
torque:
the higher ratio will produce torque. My bravo 3 is setup in 2.0:1. This helps the boat get on plane (faster and stay there at slower speeds). What it loses is top end speed. I’m seriously jealous of you 3digit guys. But my boat spends most of its life high speed trolling in rough water. 6-8’ is normal here.
Top speed:
but lower ratios like 1.5, 1.36 etc will allow much higher top end speed assuming it has enough torque to get on plane. Of course props factor into this equation etc. I have 20p and 22p duo props but I expect I’ll be propping all way out to 24-26p to compensate for my torque monster. And remember I’m on a dual prop which seem to be geared differently than normal single props. I wanted the boat to run straight when I need to leave helm to wrestle in a fish if I had no competent help on Baird. Trust me that struggle is real.
similar to truck towing axle ratios the higher the number more it can tow (torque) but lower top end speed and worse fuel economy.
this is my best understanding and many much more knowledgeable people on this board. But I’m starting to toy with this myself but I want to find the perfect setup now and then start making small changes before I get too radical (gear change).
01-09-2023 | 09:17 PM
#12
Offshore Cowboy
Joined: Nov 2002
Posts: 1,930
Likes: 34
From: Houston, TX
Couple of main reasons (and many more specific reasons, for tweaking performance):
Here's a 'main reason' example: if you're running a 36 B1 4 blade, the prop is terrible. You may wish to drop from 1.50's to 1.36's, to get to a b1 29/30/32 4 blade, which handles much better. You won't necessarily 'lose' acceleration, if you re-pitch properly. Before changing drive gears, you may perhaps speak with an expert to see if changing to a different Prop rake, brand, different number of blades, larger / smaller diameter, etc... Obviously changing props will also effect the attitude and performance of your boat... hence, the consideration of finding what prop works best for your boat, and then backing into the rest, considering the boat, it's set-up, power and drive package, etc...
Another of the 'main reasons' for daily boaters is ease of getting on plane.... which is simply achieved in more of a 'macro' step (re-gearing) vs the micro, changing props. For example, many T/S TG's were not fond of getting on plane with B1 4B 32P props. Most TG owners agree changing / tweaking the prop was a better solution (for 525 and similar powered boats) vs than the drive gears (unless you were willing to give up top-end for mid-range performance).
Bottom line... get a professional to assist... and if not, having your buddy film you as you cruise by is an easy way for 'you' to see the attitude of the boat, as you're making changes, vs taking your buddy's word for it.
Hope that helps.
Here's a 'main reason' example: if you're running a 36 B1 4 blade, the prop is terrible. You may wish to drop from 1.50's to 1.36's, to get to a b1 29/30/32 4 blade, which handles much better. You won't necessarily 'lose' acceleration, if you re-pitch properly. Before changing drive gears, you may perhaps speak with an expert to see if changing to a different Prop rake, brand, different number of blades, larger / smaller diameter, etc... Obviously changing props will also effect the attitude and performance of your boat... hence, the consideration of finding what prop works best for your boat, and then backing into the rest, considering the boat, it's set-up, power and drive package, etc...
Another of the 'main reasons' for daily boaters is ease of getting on plane.... which is simply achieved in more of a 'macro' step (re-gearing) vs the micro, changing props. For example, many T/S TG's were not fond of getting on plane with B1 4B 32P props. Most TG owners agree changing / tweaking the prop was a better solution (for 525 and similar powered boats) vs than the drive gears (unless you were willing to give up top-end for mid-range performance).
Bottom line... get a professional to assist... and if not, having your buddy film you as you cruise by is an easy way for 'you' to see the attitude of the boat, as you're making changes, vs taking your buddy's word for it.
Hope that helps.
