walleyemaster Posted April 15, 2011 Report Share Posted April 15, 2011 (edited) ok.. is there a general rule of thumb when it comes to down sizing and up sizing your propeller diameter and pitch. i have a suzuki -150 and it takes a 14.5 x 25 propeller now works perfect. i know if i change to a 13 3/4 x 25 this will increase my rpm's but by how much??. i would also like to purchase a (4blade) prop size 14 x 25 will this increase my rpm's or decrease and by how much. looking for the experts here.. thanks Edited April 15, 2011 by walleyemaster Link to comment Share on other sites More sharing options...
Fisherman Posted April 15, 2011 Report Share Posted April 15, 2011 Here's the rule of thumb, bear in mind keeping the same diameter: If you're changing pitch on a recreational boat, remember that each inch of pitch is worth about 200 rpm.Lowering the pitch will increase rpm and vice versa. For example, going from a 23 pitch to a 21 pitch will increase engine rpm by about 400 revolutions. Link to comment Share on other sites More sharing options...
walleyemaster Posted April 15, 2011 Author Report Share Posted April 15, 2011 Here's the rule of thumb, bear in mind keeping the same diameter: If you're changing pitch on a recreational boat, remember that each inch of pitch is worth about 200 rpm.Lowering the pitch will increase rpm and vice versa. For example, going from a 23 pitch to a 21 pitch will increase engine rpm by about 400 revolutions. what if i keep the same pitch but change diameter by 1/2 an inch ?? Link to comment Share on other sites More sharing options...
Garnet Posted April 15, 2011 Report Share Posted April 15, 2011 You can also change your rpm by raising or lowering your motor. The 4 blade will carry weight better and be a little slower. So if your 3 blade dropped 10 mph with heavy load the 4 blade might drop 3-5. Link to comment Share on other sites More sharing options...
Fisherman Posted April 15, 2011 Report Share Posted April 15, 2011 what if i keep the same pitch but change diameter by 1/2 an inch ?? I just guessing but I would think you would increase/decrease by 100rpm, i.e. larger diameter would decrease the rpm. Link to comment Share on other sites More sharing options...
Garnet Posted April 15, 2011 Report Share Posted April 15, 2011 Type and style of boat will change numbers. If you post what you got and what you want would help. You can also change those vent holes with different style plugs to adjust hole shot. Link to comment Share on other sites More sharing options...
walleyemaster Posted April 15, 2011 Author Report Share Posted April 15, 2011 i have a 19 foot harber craft with a suzuki 150 hp four stroke. the prop size i have on now is working well i hit my 6000 rpm and im getting about 53-56 mph according to my gps. im looking at buying another prop because my prop got dinged and i want a new one. if i need a new one it will cost me about $600 i found a couple on ebay that are the same pitch but different diameter so i have a 14 1/2 x 25 and i found a 13 3/4 x 25 for $200 i also found a 4 blade propeller 14 x 25 for $ 220. so this why im asking. will these props make a huge diffrence. Link to comment Share on other sites More sharing options...
DRIFTER_016 Posted April 15, 2011 Report Share Posted April 15, 2011 i have a 19 foot harber craft with a suzuki 150 hp four stroke. the prop size i have on now is working well i hit my 6000 rpm and im getting about 53-56 mph according to my gps. im looking at buying another prop because my prop got dinged and i want a new one. if i need a new one it will cost me about $600 i found a couple on ebay that are the same pitch but different diameter so i have a 14 1/2 x 25 and i found a 13 3/4 x 25 for $200 i also found a 4 blade propeller 14 x 25 for $ 220. so this why im asking. will these props make a huge diffrence. You should gain 100-200 rpm with the 13 3/4 and you will probably lose about the same with the 4 blade. The 4 blade will drop a couple of mph on top end but will come out of the hole better and grab better in the turns. The 13 3/4 may lose a couple of mph on top end and will lose just a bit on the hole shot. Link to comment Share on other sites More sharing options...
irishfield Posted April 15, 2011 Report Share Posted April 15, 2011 Rob.. if that prop works perfect.. just get it repaired or turn some of that hard earned marble money into a new replacement and keep the dinged one for your spare.. Link to comment Share on other sites More sharing options...
walleyemaster Posted April 15, 2011 Author Report Share Posted April 15, 2011 Rob.. if that prop works perfect.. just get it repaired or turn some of that hard earned marble money into a new replacement and keep the dinged one for your spare.. your probably right wayne, "i should stop being tighter than two coats of paint" and buy the right one. it just pisses me off i hit a rock at the bay of quinte traveling 2-3 miles per hour while i was having a pee. my buddy took the wheel i was facing the back of the boat an i heard clunc, clunk, bang, crunch. the prop was dinged on all three blades.we were in 25 feet of water he was getting his rod ready and did not look at the finder. Link to comment Share on other sites More sharing options...
irishfield Posted April 15, 2011 Report Share Posted April 15, 2011 I hate when them channel markers sneak up on you like that!!! LMAO !! Link to comment Share on other sites More sharing options...
walleyemaster Posted April 15, 2011 Author Report Share Posted April 15, 2011 I hate when them channel markers sneak up on you like that!!! LMAO !! no marker and not to far from the dock water drops to about 1.5 feet Link to comment Share on other sites More sharing options...
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