props for a 27x10 sea ray sundancer

[yellowbelly]

pulled the boat for the year this afternoon and want to re prop for next season.. the boat is 27' x10' aprx. 7000lb twin 305's 230hp alpha ones gear ratio 1.5. right now with 60 gallons of fuel im running 30mph @ 4000 rpms and thats 3/4 throttle.with 23p alum. props , i opened her up for a second to see what max rpm was and it got around 5400 rpms.. i need to drop those rpms about 1000rpms and want to go to stainless 4 blades,, what pitch is gonna be best... this bot comes off plane around 3200 rpms so i hope new props help that issue

 

[alldodge]

Ya know they made the 230hp in two variations that I can find from 1981 to 1995. This may not be an issue but just to help us understand everything that you already know, it would or could help if we knew, maybe the year. May not but sometimes ya never know.

max rpm was and it got around 5400 rpms

I don't think this is happening because you would probably be asking why your engines blew up. You do need to get it down to the 4200 to 4600 rpm, but my guess is your tach is off somewhere above 4K. I'll even venture your in the ball park.

Need to know current prop pitch (I'll guess 15)

If you do have 19 pitch props your slip is around 20 percent

 

[yellowbelly]

sorry forgot to state the year, boat and motors and drive are 1984. was told by the old owner the boat had 23p props on it, i will know for sure later today when i pull them off,

 

[steelespike]

Agreed; your props aren't 23" and 15 sounds about right. It appears you have a whacky Tachy.

 

[yellowbelly]

props are indeed 23p just ran to the shop and took them off... motors are actually 305's 228hp

 

[alldodge]

props are indeed 23p just ran to the shop and took them off... motors are actually 305's 228hp

This is making things worst, your current settings is saying you now have 48% slip. Are your speed reading from a GPS or boat speedometer?

 

[yellowbelly]

gps, could these have a different gear ratio maybe? when i power wash the crud off everything ill see what i can find out about the drives... boat jumps out of the whole great, idles around 950rpms according to the tachs, when i had them running at 5400 rpms its sounded like my outboards running at 6k, ive olny owned outboards so i/o's are new to me

 

[alldodge]

gps, could these have a different gear ratio maybe?

You probably have a different ratio, at least that would be my first guess.

 

[yellowbelly]

when i wash it this week ill see what i can find thanks,, ran to the boat real quick cause its bugging, the only thing i could find was a serial # 6714589

 

[yellowbelly]

1.98r is what ratio they are

 

[alldodge]

1.98r is what ratio they are

That takes you from 58 to 31% slip, could be getting close but need real speed and rpm numbers

 

[Bondo]

1.98r is what ratio they are

Ayuh,... That ratio is only used with the in-line 4 cylinder GM motors,....

I'd sooner think yer boat has a 1.65:1 ratio,.... or it Should have anyways,.....

 

[yellowbelly]

Ayuh,... That ratio is only used with the in-line 4 cylinder GM motors,....

I'd sooner think yer boat has a 1.65:1 ratio,.... or it Should have anyways,.....

dont know why this boat came from the factory like this, had my brother in law double check today and they are 100% 1.98,only keeping this boat one more season then its on to a newer model,,runs great jumps on plane right away i just wanted to bring the rpms down to the range they should be

 

[Bondo]

dont know why this boat came from the factory like this, had my brother in law double check today and they are 100% 1.98,only keeping this boat one more season then its on to a newer model,,runs great jumps on plane right away i just wanted to bring the rpms down to the range they should be

Ayuh,.... I really doubt it came from the factory that way,....

You'll need 2 different drives, 'n 2 different props to change it,....

 

[yellowbelly]

Ayuh,.... I really doubt it came from the factory that way,....

You'll need 2 different drives, 'n 2 different props to change it,....

i talked with the guy who bought the boat new today, those are the motors and drives the boat came with from the factory..gonna talk to the local prop shop this week about a set of 4 blade 27p props

 

[alldodge]

Suggest getting an accurate hand held tachometer. Something isn't right, speed, rpm, pitch, ratio, your slip is way to high. Need some accurate numbers from something