Hoping Bob reads this. Installed 2 496 HO's with 25 3 blades went 68.5. It has old style bravo 1's. Iwas hoping for 73. I have a 1990 scarab Viper. I was told to try IMCO 2" shorties. Little beyond budget maybe next year, as I learned the drives sit very low...

Bob who? What RPM were you turning at 68.5? What condition are the engines you installed, new, used, rebuilt?

Thanks for the responding. It was just at 4950 - 5050, and trimed out at 7-8. The engine are 295 hours out of another boat. I could not swing anything more. Engine compression good and low hours on run time. I have the scans. I believe I was told a person named Bob have my same boat that is modded out. I know a couple here around Baltimore that also have the same one. I had them check for a hook in the hull and it does not have one. I know over the internet is impossible to say, just reaching out. Thanks again

I would think you're a little low on RPM., but again, I would think 496s being the torque monsters they are, would have pulled 25ps better. Should be looking at about 5500 as your target RPM, hopefully some speed may follow. Do you know the Bravos gear ratio? Depending on the X-dimension of the drives, drives could be a bit low and putting you where you are now. A lot of factors to consider when chasing that "just 5 more MPH" that seems to be the performance boater's mantra! I wouldn't think 73 mph is not an unreasonable expectation for a properly set up Viper with that power, all things acting as they should.

The Bob you are referring to may be Jetmech on the boards? He runs down on the Chesapeake I believe and does have a well running Viper. If that is who you are referring to, you may have better luck on Speedwake? As for RPM, you are definitely in the factory range. Not knowing the year of your engines, you may want to check what the rev limiters are for your particular set up and work from there playing with props? Speaking of set-up, assuming proper trim and tab placement during running, you may want to check drive alignment. Have seen plenty of boats leave speed on the table due to drive alignment issues. Just food for thought?

My Viper ran 76 mph with hp 500 carb (470 hp) engines turning 26 labbed bravo one props when I got it ... About 100 hp more than your 496 ho's... so your not that far off for your power . Try a different set of props first off .Try turning the props inward rotation ( just run the shift levers backward for test )... might pick up a couple mph , but not worth it in my book ... makes it tough around the docks . I'm almost running twice the hp as you so my set up isn't going to help you much ! The boat has a long pad so its gonna run flat . the more speed the greater lift you'll see from the strakes . Your drives are set around 7 inch below the running surface ... - 2 shortys helped my top end but lost aprox 5-7 mph @ cruise . Currently turning 32's @ 5500... 94 - 95 gps ... installing some new heads AFR 320's ... my goal is upper 90's maybe 100 ? Current heads are 290 edelbrock oval ports ... matched to my intakes.

Haven't been on S/W in years ...

Funny you mention drive alignment. Last night I measured and the center drive nut to center drive nut is 34 1/2. I have toold it is a 34", so maybe ? The alignment bars are bottomed out and can not be adjust in any more. I was going to look into how to get replacements to get them adjusted more for the 34". I was told the drivers are 1.5 old style bravo 1's. The engine are alos 2004's

Try running your toe 1/8 " out from center ... ( adjust the bar so the the leading edge center to center is 1/8 inch more than the trailing center to center . I have a spare 34" tie bar collecting dust in my shop if you need one ... like new Latham marine ... $250 .00 includes saddle mounts .

443-350-0713

Bob

Okay got one answer, as my transom was cut low for different drives and my tie bar was wrong. Got correct tie bar. Working on solution for drive height. Feel fetter know what to address now.