Unsure if a different prop is needed

[skyviper]

I am a new boat owner and have slowly been making modifications and repairs to my newly purchased boat. I have a 2004 Larson 180 SEI with a Yamaha 115 outboard motor. I went online to find out the motor specs to see what the manufacturer specs were on it and to see if the prop I had on it was the right one.

The motor has a wot rpm of 4500-5500 as per the manufacturer. I've noticed that when running it on the water I max out at 4200 rpm with a ~500lb load and a Solas 13"x21" stainless prop. I've been doing tons of reading here on iboats but can't seem to determine what the additional benefits are of changing out my prop besides bringing my wot rpm into the max range of my motor. Will I see higher acceleration, max speed etc?

Any input on this would be greatly appreciated.

 

[Dhadley]

Re: Unsure if a different prop is needed

A 21" seems a bit agressive just as a gut feeling. We'll assume the motor is mounted all the way down and there is no jackplate or offset. If so, we'd start at a 17", maybe a 15" 3 blade stainless with decent lift to establish a baseline. If you are trimming the motor and cannot get more than 4200 the motor is lugging severly.

 

[skyviper]

Re: Unsure if a different prop is needed

The most I can get is 4200, 4000 on rough waters. I was thinking of stepping down to a 19" or 17" to bring me closer to 4800-5100 rpm range. What am I going to see in regards to noticable gains? Speed, acelleration etc...