Prop question

[1956olds]

I just went on the new searay site and while browsing found that a one year older boat with the same engines had 18X20c props,there was no prop matrix for my year but it is the same boat.I belive my props are 18x19 not sure of the cup.I do have the spec sheets from when i had them scanned and straightened before purchase some where.Point is ,how much differance between these two props?With a larger prop and cupp would i gain anything or lose something on one end or both?

 

[dpmulvey]

It's not going to be launch time in NY for a while. I would recommend "The Propeller Handbook" by Dave Gerr. It takes all things confusing about props and puts them into English.

 

[dwna1a]

May I also suggest Black Dog Propeller. They were very helpful. I used Michgain Wheel. They and many friends here helped me find the right props for my 88

 

[1956olds]

Not looking to change them this year and fairly happy with them also,but in the future if i came across a set i might pick them up even if they needed a tune-up .I am working 6-10's so i havent had time for much reading this winter,or boat working either.

 

[fwebster]

The important thing in this question is engine loading. Do your engines develop rated WOT rpm's with your props? If so, going to a 1" steeper pitch is going to reduce your WOT RPM's and increase engine loads to the point where you will need to decrease cup or pitch on the new props to regain your lost RPM's.

 

[bigcam]

I don't think those specs are for your boat. I had a 400EC with 315hp Cummins engines. 1.53 IRM 220 gears. I turned 20x24 cupped 3 blade props at 2950 rpms with full fuel and water. I would guess that if you have similar gear ratios, you would need slightly less pitch. 18X19 sounds like a gas engine prop.

 

[dwna1a]

Have you called SeaRay or email?

 

[1956olds]

They didnt have any info for me at searay for a 1992 370 with diesels only gassers.That is why i looked at the 91 350(same hull).I understand Franks insight also thats why i asked.Bigcam the beam on my 370 is 12'4 a lot less than your 400 in terms of weight also i imagine,i only carry 250 gallons of fuel for one thing.

 

[bigcam]

beam was 13' 300 gal fuel,100 water. your props will be close to mine IF your transmission gear ratio is the same.