what speed for 388 w/600sci
 

The boat has 600s with extension boxes and bravo 1 30 pitch props. I was expecting this boat to run 90 plus but it requires alot of trim to get over 85 then starts walking and hopping. Any advice on this?

Try turning the props in, should calm down the rear end. May try bigger props, what gear ratio are you runnings? This is what we have done to our old Slingshot.

Ben

Ok thanks, I will try that and report back. I am unsure what the ratios are, is that stamped somewhere on the drive? My other question is what is the approx cost and speed increase associated with speedmaster lowers on the XRs.
Thanks, EY

Not sure, we had reg, XRs on Stelling boxes, had some issues, went with imco scs, tried 1 inch shorter lowers, didn't work so we put the spacers back in to regular height, all went well after that.

Whats your top rpm you have reached so far?

what rpm was the 600hp at?

The Imco is faster than the sportmasters imo.With extension box's you could run 2 shorties,unless the set back raises the prop line?

You prob have a 1.50 gear.
30p4bl bravo,1.50,500efi 84-85,5250-5300,from the Hustler factory test sheets Ive seen ,86.7 to 88.9

theres a few thing that could cause the chine walk,something loose or worn in drive or sterr.If not ya got to learn how to balance it,I also have to over trim the drive to get that last few mph over 100.not sure what the extension box would do to it,Also thought about 5 blades,but the extra b able will give it more stern lift.it has to much lift above 90.hope this helps

rob

HEY Strip can you run the -2 imco shorties on a 388 without the extension box?

Ive never heard of anybody doing it .The 388 already has a high x,I would think it would need 5blades at least,maybe real hard to get on plane? Most of them Iv seen have box's.Joe at Hustler told me that the extension box doesn't help.I see allot of 388 with them,maybe their trying to calm the chine walk?

I just wish I could get the porpoising out of mine:(

Maybe Shawn from Canada will chime in,he's done a lot of testing .http://www.offshoreonly.com/forums/members/soinc.html

Rob:ernaehrung004:

Thanks Strip
Someone told me that on a conventional hull, if your prop shaft measured about 6 inches below your hull you could use the shorties. Wasnt sure if this applied to step hulls or not. Friend of mine with a 388 is redoing drives and was debating on the shorties. Wanted to make sure they would work before spending the dough!

maybe -1's would work? do you think the imco standard length would be of any benefit with the more efficient lowers?

if your buying them get the -2, you can put a spacer in it.I think with the -2 maybe smaller dia? also if ya put the 380 tabs you will have to trim them.

if your comparing Imco to stock xr.sportmaster etc. I think the Imco is faster and looks cool to:rolleyes::drink:
I went from stock xr lower to the B max lower.the casting was real fat.there was no speed change,now that Ive cut them down Ill see this summer.

maybe someone else will ad some input.

Rob:drink: