what prop

[forceproblem]

looking for a new prop had an aluminum 15pitch 13 dia 3 blade its on a 1987 force 125 on a 19.5 ft bayliner capri not sure weight it runs at wot about 4400 rpm if tach is correct i have a chance to buy a exact same size prop with a 17 pitch in stainless what should i expect to change i mostly do tubing it does fine as is but a new prop is needed i want to bring the rpm up to a better operating range. some of the reason the wot is low right now was the trim wasnt trimming up underload fixed that prob any opinion or advice would be helpfull thanks

 

[evin/skeet]

Re: what prop

going up to a 17p prop will make you lose rpms comeing out of the hole but will increase your speed on the top end

 

[forceproblem]

Re: what prop

will i gain anything with stainless ?

 

[Bob_VT]

Re: what prop

You have something wrong. You are NOT achieving WOT and proper rpms. You might have a motor problem and NOT a prop problem. You need to diagnose why you are not reaching 5500 rpms then re-consider the re-propping if needed.

Moving up to a bigger prop now might finish off that motor by further lugging it....... NOT a good idea at all.

 

[evin/skeet]

Re: what prop

im having the same rpm issue with a 140 evinrude my only hits 4200rpm wot if u figure out what it is please post it

 

[forceproblem]

Re: what prop

i guess i should explain better the tach is stuck at 2000 rpm the best it ever reads is 4400 rpm but going by sound i know its higher then that but io will go threw and check everything again but im pretty sure its running perfect so i guess i dont know rpm till i fix the tach now youve got me worried there is a problem with the motor not like that is uncommon in these engines i have good compression strong spark and good fuel flow and freshly rebuilt carbs interesting though i really need to fix that tach

 

[Bob_VT]

Re: what prop

:facepalm: Yes, fix/replace the tach first.

 

[Frank Acampora]

Re: what prop

IF the stainless prop is NOT cupped, you will probably reach just about the same RPM and probably 1-2 MPH more. If it is cupped, then RPM will drop a bit and speed may stay the same or may drop a bit.

Never mind what the engine sounds like! The human ear is notoriusly inaccurate at determining RPM. The ONLY way is to read an accurate tachometer. Yes, definitely repair or replace the tach. The combination of accurate RPM readings and a GPS for accurate MPH will tell you how well your engine/prop/hull is performing.

 

[forceproblem]

Re: what prop

ok thank you i will work on that first