wieland77

I bought a 1987 28' Saber a couple months ago and I was able to run it for the first time this past Sunday. I dont know anything about what was done to the motor accept it was recently gone through by More Power in Grand Rapids, MI. They replaced the rings and a piston, put in new bearings and polished the crank and cam. It has IMCO manifolds and a hi-rise Dart intake with a 950hp double pump Holly carb. I do not know the HP rating for the engine.

It has a 25 pitch 3 blade mirage prop on it and when running wide open I was running around 4700-4800 rpm and on;y getting 57 - 58 mph depending how the drive was trimmed.
Is this prop a little too much for the engine. It seems like I should be in the 5100 - 5300 rpm range. I dont know a whole hell of a lot about props and what would be the best match for what I have. I have a 1.5-1 Drive.

Am I where I should be or should I go with a different prop, and if so what one? Any info would be appreciated.

Whiteknuckle

I know the 28 Sabre is a heavy boat, but it appears you have a lot of slip with a 25incher at 58MPH. I also agree that you should twist that engine up to at least 5000 RPM. Is the bottom good a clean? is the prop in good condition? I just think it should be somewhat more effecient than what you are seeing? Maybe a 4-blade Bravo would be a better choice for that heavy of a boat.

wieland77

Yah,

Bottom is very clean and the prop is in really good condition, no dings or anything.

KAAMA

Testing a few props out first would be the best thing to help you narrow down the problem as Whiteknuckle has suggested. Plus, anything More Power can give you about the the cam specs would be beneficial....if they will tell you. Even if they don't want to reveal the cam specs just ask them at what RPM level the engine should be making it's peak or close to peak power at with the cam they have in it, then perhaps it should get you closer to where you need to prop it. Also, an 800cfm Holley carb vs a 950cfm may be more suitable for a marine 502cid engine.

Payton

Using 4800 RPMs and 58 mph that calculates out to 24% slip.
I agree that your RPMs most likely should be 5000 or so, But, you need to get that slip down. Does the boat feel like it is running with the bow down?
Are you running a Mirage or a Mirage Plus? There is a lot of difference.

Darkspoilerzx

I would think that a four blade would get that slip down, to an exceptable level as far as where to go with pitch see if you can borrow someone 23 bravo four and see what that does for ya. Propping can be expensive and a pain but trial and error is still the best way get some and go to the lake a try them. I would also swap an 800-850 for the 950 carb. Ed

oblvnxprs

502 x 5300 /3456 = 769 cfm I would definatly try an 800 carb and then start trying diferent props
I can get a better top speed out of my 3 blade (71.8)
than my 4 blade (70.1)
but the 4 blade is a whole lot better to run it has a better cruising speed by almost 10 mph at 3600 rpm
darryl

Mr Gadgets

I would think if slip was the issue the rpms would be a lot higher than lower. If the HP and Torque are there, then it would seem the the prop would cause it to over rev and speed would be down. Are you over trimming it to get that speed. It sounds like it is running on 7 cylinders.. I would check the health of the motor first, then look at setup. The 28' Saber has been run with three blade props for years and done very well. Unless someone has changed drive height, etc.

I would look at the motor first... I have been there done that. Sometime MorePower isnt more.. but thats another story..

jpclear

I think Mr Gadgets got it. Get it running on all 8 cylinders, then do what darryl said and get a more effective, lower cfm carb. on it. --- Jer

vandeano

I have a 1988 27' Carrera w/ 502 V stock except that I changed motor to a roller set up with revolution marine exhaust. With a 25'' Mirage I was running at 4900 rpm and speed was 59-60 mph on GPS. RPM would probably be up more then 4900 but the slippage was so bad I would pull back on the throtle, especially out of the hole.

Then I tried a 26" Bravo 1 four blade. Speed was 63-65 GPS at 4200 rpm. no slippage at all. Problem was that not enough power to turn it. To me it felt good, I loved the way the motor sounded at WOT. Wasn't screaming like it was getting ready to blow up at 5000 rpm. But from what people have told me I guess that was putting to much load on motor to only turn it at 4200 rpm. To me it was perfect it would get to 4200 rpm in no time but that was it. Crusing speed was fantastic, out of the hole was fantastic. The only downside was the 4 blade did give me major chine walk at WOT when boat had only me in it and a 1/4 tank of gas.

So I tried a 25'' Mirage "PLUS" Speed is 60-62 at 4500-4600 rpm. You can feel slippage when you play with the trim. There are times when I have to come to a stop so that the slippage will stop. The next prop I will try a 24" Bravo 1 labbed. I really like the way the 4 Blade picks up the boat with out the feeling off slippage.