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Ya i googled it and found the list. looks like Chinese to me. lol I did call the dealer and he explained the difference. They said a 1.66 ration lower unit would be a little faster then my 1.6 ration if we are running the same size prop. around a 5 mph difference. He said I would have to drop in prop size to get the Rpm's up to produce the HP to get the top speed with my ratio. Sounds like I would need to go to a 19P to hit the 50's mph mark. Does this all sound correct. Thanks guys for all the input. I learn so much on here.

Ahh sorry, My rpms are around 4100 -4200 hitting around 47 mph with a 14.3 x 21 Prop. I am going to get the boat out this weekend and work on my Trim and only have two people in the boat and see what she does. I do know I am somewhere in the mid 40's. I have seen better speed out of the new prop.

I remember seeing a chart once where the combinations of upper and lower gear ratios were detailed to give the different overall ratios. I'll have a look to see if I still have a copy somewhere.

Author:	Toddely [ Thu Jul 25, 2013 6:50 am ]
Post subject:	Ratio Question.
Hey all, quick question. after talking to Deafwish his lower unit is a 1.66 ratio, Just looked at mine and my tag says its a 1.60 ratio I dont know how ratio's work but is .06 ration much of a difference. working on my speed and rpm issue. Comparing to Deaf's boat. He has the exact set up and boat. just a little difference in the Ratio. Thanks

Author:	afw200 [ Thu Jul 25, 2013 7:27 am ]
Post subject:	Re: Ratio Question.
See attached VP drive chart for plethora of drive ratios in the SX. http://www.volvopenta.com/SiteCollectio ... 745608.pdf

Author:	Toddely [ Thu Jul 25, 2013 8:01 am ]
Post subject:	Re: Ratio Question.
To me it sounds like this could be the difference in WOT rpm's and Top End Speed. I do notice a speed difference since I put a new Volvo Penta 14.3 x 21 aluminum prop. Had a 14.25 x 23 aluminum pro on it. My hole shot is better now as well as my Top speed. Was hitting around 40-42 mph (GPS) now I am at 47 mph (gps). Wondering if a 14.25 x 19 would make it even better or take it the wrong direction. And lets face it how often are running WOT. I guess its a guy thing and like to know you can go that fast

Author:	Graham R [ Thu Jul 25, 2013 8:08 am ]
Post subject:	Re: Ratio Question.
I remember seeing a chart once where the combinations of upper and lower gear ratios were detailed to give the different overall ratios. I'll have a look to see if I still have a copy somewhere.

Author:	Toddely [ Thu Jul 25, 2013 8:15 am ]
Post subject:	Re: Ratio Question.
Ya i googled it and found the list. looks like Chinese to me. lol I did call the dealer and he explained the difference. They said a 1.66 ration lower unit would be a little faster then my 1.6 ration if we are running the same size prop. around a 5 mph difference. He said I would have to drop in prop size to get the Rpm's up to produce the HP to get the top speed with my ratio. Sounds like I would need to go to a 19P to hit the 50's mph mark. Does this all sound correct. Thanks guys for all the input. I learn so much on here.

www.iFourWinns.com https://www.smwebhead.com/phpBB3/

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Author:	rpengr [ Thu Jul 25, 2013 9:52 am ]
Post subject:	Re: Ratio Question.
Toddely wrote: Ya i googled it and found the list. looks like Chinese to me. lol I did call the dealer and he explained the difference. They said a 1.66 ration lower unit would be a little faster then my 1.6 ration if we are running the same size prop. around a 5 mph difference. He said I would have to drop in prop size to get the Rpm's up to produce the HP to get the top speed with my ratio. Sounds like I would need to go to a 19P to hit the 50's mph mark. Does this all sound correct. Thanks guys for all the input. I learn so much on here. When you post your speed, please post your RPM also. The two go hand-in-hand. Example: If you are getting 47mph at 4200 or 4400 rpm, then yes...switching to a 19 pitch will increase your speed further. If you are getting 47mph at 4800 rpm, then you have reached your peak. ps. The difference between 1.66 ratio, and 1.60 ratio, is only about 4%. That equates to a little less than 1" of prop pitch.

Author:	Toddely [ Thu Jul 25, 2013 10:21 am ]
Post subject:	Re: Ratio Question.
Ahh sorry, My rpms are around 4100 -4200 hitting around 47 mph with a 14.3 x 21 Prop. I am going to get the boat out this weekend and work on my Trim and only have two people in the boat and see what she does. I do know I am somewhere in the mid 40's. I have seen better speed out of the new prop.

Author:	rpengr [ Thu Jul 25, 2013 11:07 am ]
Post subject:	Re: Ratio Question.
Toddely wrote: Ahh sorry, My rpms are around 4100 -4200 hitting around 47 mph with a 14.3 x 21 Prop. I am going to get the boat out this weekend and work on my Trim and only have two people in the boat and see what she does. I do know I am somewhere in the mid 40's. I have seen better speed out of the new prop. 19 pitch might get you to 50 mph, but on the other hand, I am thinking that you are not getting full horsepower. 21 pitch sound right for your boat, but you should be getting more RPM. I would do a compression check. You could have a bad cylinder, and still have a smooth running engine. If the engine checks out OK, then try the 19 pitch prop. Read this: http://www.perfprotech.com/blog/articles/marine-engine-condition-2#

Author:	Toddely [ Thu Jul 25, 2013 12:15 pm ]
Post subject:	Re: Ratio Question.
Ohh boy.. I hope not... lol That would suck. Ya thats the weird part, It runs great, no rattles, smooth as can be. I figured she is just not as young as she used to be. I just baby her and cruise around 20mph most of the time with the admiral.

Author:	deafwish [ Thu Jul 25, 2013 4:09 pm ]
Post subject:	Re: Ratio Question.
Play with your trim, the results are surprising! Is your speed via GPS, or the dash? I have 4-2-1 marine extractors on my 5.7, which should be giving me some more ponies than your cast iron manifolds/ risers... I also have the exhaust exiting at the transom plate through a flap (no bellows). Sounds tough!

Author:	Graham R [ Fri Jul 26, 2013 4:43 am ]
Post subject:	Re: Ratio Question.
Graham R wrote: I remember seeing a chart once where the combinations of upper and lower gear ratios were detailed to give the different overall ratios. I'll have a look to see if I still have a copy somewhere. I found them again, originally posted by someone on Boating ABC some years ago ! Upper (SX and DP-S): 3857007 BRP HSG AY,GEAR 22:23 (1.43, 1.51, 1.60, 1.66, 1.68, 1.78, 1.95) 3857010 BRP HSG AY,GEAR 21:26 (1.79, 1.89, 1.97, 2.18, 2.32) Lower (SX): 3855692 BRP G'CASE AY,SX 19:26 (1.43) 3855693 BRP G'CASE AY,SX 18:26 (1.51 and 1.79) 3855694 BRP G'CASE AY,SX 17:26 (1.60 and 1.89 ) 3855695 BRP G'CASE AY,SX 17:27 (1.66 and 1.97 ) 3855696 BRP G'CASE AY,SX 17:30 (2.18 only ) To get the final ratio value, multiply both ratios together. So , e.g. for 1.79 Upper 21:26 and Lower 18:26. So the final ratio is (2626)/(2118) = 1.79

Author:	Toddely [ Fri Jul 26, 2013 7:19 am ]
Post subject:	Re: Ratio Question.
I forgot about you changing out your risers. They look awsome by the way, can you send me a pic of your exhaust. Did you have that done or did it come that way. Well this would explain some of the speed differences between our boats as well. I am getting ready to post some pics of some findings on mine last night. Thanks for the input. Oh my speeds were gps as well.

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