Just purchased a 38 excel Scarab 1990 with TRS drives, mild build on 425hp 454 and 4 blade props I am told are 23p. The owner says they pull 5600 but the motors are built to 5800. On the test drive it would cavitate big time out of the hole. Ran ok on plane but took work to get there. I have a set of Mirage 23p three blades on another boat, would these be better? Could the 4 blades be made to work?

Who makes the 4 blade props?
Try the 3 blade props for sure sine you already have them.
Yes the 4 blades most likely can be improved.
More testing and information will help.

Brett

Took it out yesterday and they brake loose as boat wants to plain. While running at lower speeds 20-30 they brake loose from thim to time as I hit waves or turn the wheel. The syncro tech pegs one way then pegs the other.

your spinnin g 425HP with a 38 footer and TRS 4 blades to 5600?? wow

I cant get my 480 hp to spin more then 4700 with 23P 3 blades...in a 35 Cig

I'll find out today, i'm just going by the olds owners comments. I did a short run this week and they slip A LOT.

Curious to see whats up, thats less hp then me, more boat... more rpm?? odd...especially with 23P 4 blades...unless tachs are off?

Ok took one off, today, it is stamped on the end P125b6111 RL the other is P125B6112 RL on the back it says 5. Today I cruised about 3 grand at 40 MPH. Full throttle with trim mid to out one engine ran 3800 the other was 4100 at 56 MPH on gps The syncro tech was 0 but neither tech is =. 56 is the best I've seen with this boat. Last night I tried everything to run 25 to 20 mph and it just kept blowing one then the other, night cruising is hard.

Sounds like you are having more than one problem at the same time...........
1. get the prop problem fixed ----Talk to B-Blades or call Merc racing and give them all the specs for your boat....
2. Do not depend on those old gauges to give you the right readings and Do not depend on the syncro tach at all ----they usually failed or started giving the wrong readings within 2 to 3 years of being installed from the factory.
3.Install new gauges and do not hook the old syncro back up to the new equipment.Autometers usually work the best and can be sent in for repairs if some thing goes wrong..Wellcraft used them for the last five or six years before they quit making the scarab,they worked very well without a lot of problems........Good luck


Jim

Thanks! I'm hoping b Blades chimes in with what the stamped numbers mean.

I figured the gauges were messed up and my first thought was the individual tech were more correct. Only thing make me wonder if the syncro was close is when it gets close to zero I hear the harmonics of the engines getting close to each other.

Thanks for the autometer Idea, never thought of them for a boat. I will look into them.

The numbers you supplied are not common numbers.
These are not BBLADES or Mercury numbers. Are they hand stamped or cast in?

Using a average of 4950 rpm, the props are staying hooked up.
After fixing the guages, getting new numbers will help us. It does look like you will need sless pitch.

Brett