prop??

[Speedman]

So being here in Mass and never seeing another Allison sucks! I have no one but you guys to help out so here goes...I bought the boat in 94 and have a 97 225 Pm on it, (xb2002). it came with 2 props a 29 srx and a prop that just said "Ron Hill" on it, 28 pitch? I ran the 28 for the last 10 years and discovered it had a crack outside the hub. So now I have the 29 SRX on it and it porpoise's when I go above 75? I can drive through it, but it feels like I am way too high and floating? I have never had a blow out or adjusted anything. I have the engine set at 1/2" below the pad, 10" manual rapid jack plate, new cables from Merc, full tournament load. I here tons of people talking about Chine but never heard anybody ask about porpoiseing? any ideas, I am guessing that it may be the prop can't lift my hull? what do you think? Thanks, Gary

 

[jimmyb]

i do think the porpoise in your case (since you ran the hull with different props with out the problem) is caused by the prop not being able to lift the boat properly. Since you can drive "thru it" the fast you go the more air helps lift the front of the boat and prop doesnt need to lift as much.

my advice is to have someone knock some more cup into your prop...

or buy yourself a 28ET

 

[John Richied]

Try raising you propshaft height to

 

[hack02]

I agree with John. My 29SRX is one of my favorite props. Dog out of the hole but once you get rolling it rips. You can't loose moving you engine up. You can always go back the way you had it. How much setback does your rig have?

 

[Speedman]

o.k so I am going to try a couple of things today, I just put on an Ally foil ( thanks Scooter trash!). Where exactly do I get the maesurement for engine heigt? on a level surface, the bottom of the pad is 14" from the ground, then I trim the engine and put a level on it, then measure to where? the cavitation plate, currently at 18"? the middle of the prop shaft, currently at 10.5"?, not sure where to measure it? Thanks as always, Gary

oh yeh, the jack plate has 8" of set back

 

[hack02]

The center of the propshaft. Make sure you have your propshaft as level as you can get it. Also, when you measure to the pad of the boat measure to a point a couple of inches forward of the lip.
Right now it sounds like your running your propshaft 3 1/2 inches below the pad. Most owners here run anywhere from 1/2 below to a little above. I would suggest you raise your engine about three inches, putting your propshaft at 1/2 inch below the pad for starters. Now take the boat for a ride. It'll be a different animal set up like this. After you get the feel for it you can continue to go up in 1/8 or 1/4 increments for fine tuning. With this setup, the hull will be able to perform as designed instead of dragging the gearcase through the water. I wouldn't reccomend going above the pad. Also I'm assuming you already have a low-water pickup gearcase like a Sportmaster or other modded case.

 

[Speedman]

o.k, I thought it was the center of the prop, I will raise it a little at a time, as I have driven it where it sits for 8 years! The Allyfoil worked great today with the srx prop, it really kept the nose down and also allowed me to go on plane much slower, great 50 dollar investment! next problem, I dinged the prop today, bent the leading edge of one of the ears pretty good, gotta get it fixed before I drive it any more! if I am a 3.5 inches below the pad, that's way too low for the promax/sportmaster gear box??. I guess this is also why I have never had a blow out or bat turn. and also at that low, I can trim all the way up till it trims no more. at 1/4 below the pad, will I be totally safe as far as water pressure goes? Thanks for all the help, Gary

 

[hack02]

If you have a Sportmaster the water pressure should be fine. 3 1/2 is way low. You should pick up several mph on top end. At least 5 or 6 easy.
Seems for me the Ally Foil makes alot of difference coming off plane; keeps the back of the boat from sinking so fast.
Anything up to 1/4 to even you should be relatively safe as far as the bat turn scenerio; anything more than even and you have to really pay attention.

 

[Speedman]

Thanks, so now I am in the market for a back up prop, seems I had my 28 ron Hill prop on with the wrong washer and it actually dug a groove in the back of the prop to the point where it hit the spline and cracked it, What's a good prop, I can't afford 1k for an ET! Another question, Why do guys run 26's and 27's? when they can push a 29 or 30 to the limit? not sure about the HP, RPM, Speed relation thing? I can put the 29 to the limit even at 3" below the pad? what do you think?

 

[hack02]

Go to www.screamandfly.com and go to the Props section and keep a lookout for something. Just a plain old Merc Chopper is hard to beat. Should be able to find something decent for 2 to 250.