Lower unit gear ratio Question??
#1
Lower unit gear ratio Question??
SO,
I need to buy a new lower for my outboard, I have a choice of 1.62:1, or 1.75:1 ratio. My 225 had a 1.62, and jumped on plane, since I have had the 250 with the 1.75, it was having trouble getting the boat up, but ran great up top, once it hits 2000 rpm it takes right off, just having trouble reaching that. I also know I am propped correctly, because once planed and running WOT and trimmed, I get the 5800 the motor is rated for. I know I may have some other ignition, or injector related issues, but need the lower before I can diagnose them, just want to make the right choice. Which lower will allow the motor to spin up faster?? I know I should know this, but having trouble relating it to my car days, its been a while, and just dont want to go the wrong way. Also, I am going to try the SEI lower, cant beat the price, I'll let you all know how it works out.
I need to buy a new lower for my outboard, I have a choice of 1.62:1, or 1.75:1 ratio. My 225 had a 1.62, and jumped on plane, since I have had the 250 with the 1.75, it was having trouble getting the boat up, but ran great up top, once it hits 2000 rpm it takes right off, just having trouble reaching that. I also know I am propped correctly, because once planed and running WOT and trimmed, I get the 5800 the motor is rated for. I know I may have some other ignition, or injector related issues, but need the lower before I can diagnose them, just want to make the right choice. Which lower will allow the motor to spin up faster?? I know I should know this, but having trouble relating it to my car days, its been a while, and just dont want to go the wrong way. Also, I am going to try the SEI lower, cant beat the price, I'll let you all know how it works out.
#2
Registered
The 1.75 is the engine turning 1.75 times to one rotation of the prop. So going to a 1.62 will be worse on your engine. Every engine is different depending on two stroke or four stroke. Sometimes the two strokes get more power with porting that changes the torque curve and can make the more powerful engine sluggish at slow speeds. Most of my outboard race engines were 1.87.
I would stick with the 1.75.
I would stick with the 1.75.
#4
The 1.75 is the engine turning 1.75 times to one rotation of the prop. So going to a 1.62 will be worse on your engine. Every engine is different depending on two stroke or four stroke. Sometimes the two strokes get more power with porting that changes the torque curve and can make the more powerful engine sluggish at slow speeds. Most of my outboard race engines were 1.87.
I would stick with the 1.75.
I would stick with the 1.75.
Appreciate the info, I just couldnt think straight
#5
I dont think its the props, turns the correct RPM on the high end, and as far as prop design, these are the same 2 props I used with the 225. Obviously the 250 has an ignition, or injection related problem on the bottom end, just want to get the best ratio for the boat once its figured out, also to rule that out in the troubleshooting/testing.
#8
Registered
Join Date: Apr 2007
Location: GLOC and Bartlesville, OK
Posts: 228
Likes: 0
Received 0 Likes
on
0 Posts
I do not know what engine you have but the only difference between the 225 and the 250 is the 250 may be allowed to rev higher and that is how it gets the 25 more horsepower. If this is true, it may not have any more torque on the low end and this might be the reason it is sluggish on the bottom end. In other words the 250 has to pull a higher gear than the 225 and does not have anymore torque or horsepower on the low end. If the 250 does not have anymore torque at 1000 to 1500 rpm than the 225, I would go with the gear ratio you had on the 225.
#9
I do not know what engine you have but the only difference between the 225 and the 250 is the 250 may be allowed to rev higher and that is how it gets the 25 more horsepower. If this is true, it may not have any more torque on the low end and this might be the reason it is sluggish on the bottom end. In other words the 250 has to pull a higher gear than the 225 and does not have anymore torque or horsepower on the low end. If the 250 does not have anymore torque at 1000 to 1500 rpm than the 225, I would go with the gear ratio you had on the 225.