Harper220

I'm running box stock 29p P5X's on my 28 Eliminator TD Daytona 496 ho's. They perform great compared to Bravos. Much better hole shot, faster mid-range and over all much better handling. My question: I just installed 2" Imco shorties, but haven't ran the boat yet. By adding the shorties, what will this do to my performance with the same Hydros and will I need to enhance them to work better with my new raised outdrives? Or would I be able to go up a pitch? If I have them labbed, what will this do to top end? I absolutely don't want to lose any mid-range. Any suggestions or recommendations to get the most out of my changes would help...

throttleup

What were your performance numbers before putting the shorter low unit on? RPM@WOT and speed?

You will lose mid range with the shorter lower unit, that's almost always the case.

Lab finishing for speed will also lose mid range. I am concerned that going 2" higher will be too high. The only way to know for sure is to run the boat.

I wouldn't do any prop work until you get some baseline numbers with the new set up. With some baseline numbers and some input on the characteristics of the boat, with the new set up, we can make some recommendations what would be the next step.

Matt

Harper220

How and why would I lose mid-range by adding the IMCO's?

3500 rpm = 62 mph 4000 rpm = 74 mph 4900 rpm = 90 mph

Bravos were a little faster on top end.

You've got me worried now about losing mid-range just by adding the IMCO's. Oh well, probably just a 5k mistake...

Harper220

Matt- I talked with the boys at Eliminator and they most certainly didn't tell me that I would lose any speed by doing this, so now I'm confused after reading your post. I hope this doesn't turn out to be a big waste of time and money.

throttleup

The 28 Eliminators usually have the drives from the factory mounted on the high side. That's why the P5X works well on these boats. It helps the boat get on plane much better and helps the cruise speed compared to the Bravo 1's. while maintaining a respectable top end speed.

Your slip is currently at 9%. That is about as high as I would like to see on a boat like yours. If the Bravo 1's had a difficult time getting on plane due to "blow out" then my first impression would be not to go higher with the drives.

If you have the lowers installed I would run them and see what you performance numbers are, then go from there. You still have a few hundred rpm to play with before you hit the rev limiter. You will be able to make a good decision after that.

Rarely do boats pick up speed by installing a shorter lower unit and doing nothing else. If you would like more info just give us a call.

Matt

Harper220

Matt- Can the P5X be pitched up?

throttleup

Yes, 1 inch.

Julie

bbladesprops

Harper220,

Don't get too worried yet. The drives will add some rpm to your top end. If the slip does'nt overcome the added rpm, you will gain speed. You are in the midst of a balancing act.

I'm not sure what is meant by " rarely do boats pick up speed by adding shorter lower units and doing nothing else."

We see gains on many applications by simply raising the drives. You just have to know when it is a viable option. Your application is a touchy one.

jdnca1

I see ~15% slip with Bravos and 7% with P5X. (twin 28 TD)Imco boxes and std length drives...1" below bottom of boat. I really like the way the P5X carries the bow vs Bravo, will be trying set of 2" short drives in a couple of months.....I am convinced the boat will like the short drives and gain speed....

Harper you will be fine, Eliminator knows what works. As Matt stated, I would leave your props alone to get a baseline with what you have.

throttleup

" rarely do boats pick up speed by adding shorter lower units and doing nothing else."

Meaning, typically just bolting shorties only... will not make you good to go! Usually it requires propeller work if not new propellers.

Julie