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bzsmarina
08-05-2009, 09:12 AM
hello. i have a 19 1970 donzi monza. i just built the 351 ford up to about 400 - 450 hp. also upgraded the drive from the volvo 270 to a volvo 280t with trim. i have 2 questions. one does anyone have or know anyone selling headers for the 351? also i seem to have to much slip. even with the drive swap i have the same slip as the 270. both drives have nose cones on them. and both have same 1.61 gear ratio. i seem to have 20% slip. i run a 21 spinelli and a 26 volvo ultra both props seem to have the same slip? anyone know why or do all the volvos have the same slip? thanks bz

BlownCrewCab
08-05-2009, 09:29 AM
Are your prop slip #'s at full speed? The Volvo drive is not a top speed drive, a nosecone helps. Do some prop slip #'s at other speeds and you'll see the volvo/ultra combo is pretty good. just when you try to push it too fast it punches a funky hole in the water causing slip and blowout.

BigGrizzly
08-05-2009, 09:35 AM
Your slip is because of the prop. My props have the least slip of any prop. I bet the Spinelly cavitates on turns too. The ultra is better but not great.

mattyboy
08-05-2009, 09:52 AM
try this link
http://www.hitekmarine.com.au/ford.htm

or you have to go big bucks for CMI's


the slip on an ultra is around 15% what are your numbers

bzsmarina
08-05-2009, 10:08 AM
slip # are 20% with both props

mattyboy
08-05-2009, 10:16 AM
what are your numbers


rpm?

gps speed?


Pitch 21 or 26

gear ratio 1.61


any issues with the nose cones??? are they straight? are there any irregular surfaces ?? have the drive ratios been confirmed?? what trim settings

the ultra and volvo as BCC
can get less effiecent the faster they go more the prop than the drive so WOT numbers need to be checked to mid range numbers

bzsmarina
08-05-2009, 10:33 AM
will a cleaver make more or less slip. i just did the # on a prop calculator and the slip at 3000 is 14.5% and at 6000 is 22% with the 21 and the 26

mattyboy
08-05-2009, 10:42 AM
what were the different speeds at 3000 with the 21 and the 26 and what were the speeds at 6000 with the 21 and the 26???

bzsmarina
08-05-2009, 10:52 AM
at 3000 with the 26 it ran 42 mph. with the 21 at 3000 it ran 30. at 6000 with the 26 it ran 68. with the 21 at 6000 it ran 62. will that 26 cleaver you have, have more or less slip?

Just Say N20
08-05-2009, 10:57 AM
It has been my experience the cleaver will have MORE slip. But that was with a Mercruiser Alpha now that I think about it.

It definitely didn't bite as well, and seemed to slip more the higher the rpms.

mattyboy
08-05-2009, 11:06 AM
not really sure how or what prop calc you are using


http://www.rbbi.com/folders/prop/propcalc.htm




but with your numbers on a 1.61 drive

the 21 @ 3000 rpm @ 30 mph is 19%
the 26 @ 3000 rpm @ 42 mph is 8.5%

the 21 @ 6000 rpm @ 62 mph is 16%
the 26 @ 6000 rpm @ 68 mph is 25%


the 26 is pretty much on the ultra I used were more effiecent in the mid range and became less effiecent at the high end of the range

the 21 is about the same thru out the range give or take a point or two

mattyboy
08-05-2009, 11:14 AM
cleavers are made to run up near the surface, that usually leads to more slip

I was near 15% with the ultra 24 and pretty close to that with the cleaver 26 as well but i was not spinning either past 5200 rpm I think I got the cleaver just about to 4950 in the top setting of the 250

you got similar numbers with the 280 T and the 270??? I would think with the newer bottom end of the 280 and the trim the numbers would be better than the 270

bzsmarina
08-05-2009, 11:35 AM
also the bow seem high even with the trim in all the way. with it trimed in all the way it ride like it did when it was on the 2nd hole on the 270 set up. i trim it up and the bow is standing up???????? weird i do not understand this. i figured with trim i would be able to lay the bow down a bit but the higher i trim the higher the bow goes. thats why i ask about the cleaver. i know thay give stern lift. i still have to do the hearders. i still running the hm stock headers. i have way to much water flow with them and no gases getting out. i called drew marine and he told me a way to cut the water flowing out of the risers to 10% water. i am trying this, this week. i need to re plum it and make plates and gaskets for the risers. has anyone tyred this?

bzsmarina
08-05-2009, 11:50 AM
i also had a friend drive the boat as i looked over the stern to see whats going on back their. it looked like a fire hose worth the water coming out of the hearders. i need to do more testing. i was just useing the boat speedo with i know is off. so the # i have may be bad. the calcuator i use was on hill props web site.

BlownCrewCab
08-05-2009, 11:57 AM
if you can turn 6000rpm you don't have any restriction from too much water flow. I think the velocity of the water is what your friend saw made it look like a fire hose, perfectly normal.

bzsmarina
08-07-2009, 08:22 AM
certainly not from any Hornet mold, the hornet is a hook mold look at the rocker in the hull of the monza no character line


what is the deadrise of the hull??

it is a great looking older boat that deserves to have it own history

hope you get your performance issues worked out


just spit balling but with all that rocker if she were mine i would scrap the volvo and look for an Arney ;)
if the boat has a lot of rocker in it, wont that cleaver work better. i do want to buy the prop from you. i just need to finish a few things first. but i do want it.

bzsmarina
08-08-2009, 02:00 PM
yes the cockpit does look gt ish except for the raised lip that goes around it
i know the gt has some what of a lip but the monza is more pronounced
look at the yellow one you can see it at the base of the windshield and on bz's you can see it also notice the lack of the lip on the last pic of a gt
it is what it is. now maby i can get my question answered. if the boat has a lot of rocker ( which will give bow lift ) and i put trim on it. would a cleaver help the bow up problem?

mrfixxall
08-08-2009, 07:57 PM
it is what it is. now maby i can get my question answered. if the boat has a lot of rocker ( which will give bow lift ) and i put trim on it. would a cleaver help the bow up problem?


Call my prop guy and send him your ultra,Tell him you wand alot of bow lift and a heavy cup put in it,that will take care of the slip and should give you more mph. john did both of my ultras and they gave me plenty of bow lift and the xtra cup also glues the A$$ of the boat to the water..read his back ground then on his webb site then you deside:)
Also tell him to glas bead the cup area on each blade,this will let the prop hold more water...


http://www.dahpropellers.com/

f_inscreenname
08-08-2009, 09:57 PM
it is what it is. now maby i can get my question answered. if the boat has a lot of rocker ( which will give bow lift ) and i put trim on it. would a cleaver help the bow up problem?

I know with the Nova and the Monza trim helped with bow lift. Add in a good biting prop and you are set.

bzsmarina
08-08-2009, 10:15 PM
the problem is not getting any bow lift, it i am getting to much. the faster it goes the higher it gets. also when its trimed all the way in its like the boat was before on the 2nd hole with the old set up. thats why i want to try a cleaver.

mattyboy
08-09-2009, 06:48 AM
cleavers don't give much if any bow lift they like the surface and they like to be spun fast

trimming up on a rocker hull will force the bow up higher so I am not sure you have to trim up the cleaver to get it where it likes to run but will that cause the rocker to lift the bow anyway?? the long leg of the volvo is acting like a big lever

Donzi_Dude
08-09-2009, 07:21 AM
these 24 deg. rounded keel boats, do they generally have a hard time lifting the bow to the point most are looking for bow lift?

thankx!


:pimp:

mattyboy
08-09-2009, 07:52 AM
these 24 deg. rounded keel boats, do they generally have a hard time lifting the bow to the point most are looking for bow lift?
thankx!
:pimp:


it depends on the exact hull it's length and construction type hooked, straight,rocker or padded, and the strake formation and length

ie the 16 has no problem getting the nose up

joseph m. hahnl
08-09-2009, 02:42 PM
these 24 deg. Rounded keel boats, do they generally have a hard time lifting the bow to the point most are looking for bow lift?

Thankx!


:pimp:


49139

mphatc
08-10-2009, 08:57 PM
Headers for the SBF . . .

Get the E top CMI headers . . contact Ateco Engines
http://www.atecoengines.com/Catalog.aspx?CategoryID=1

302 or 351 at any RPM you can spin that engine the E tops are more than adequete . . no need for the Sport tubes.

I have a Ford 302 +/- 400 HP that runs the E top headers . . great set up, and they don't cost $6500.00

The Aussie set up is very hard to acquire here in the states, and ugly, won't clear a Ford with larger rocker covers and roller rockers . .

Mario L.

1969 Corsican
1698 Magnum 27

bzsmarina
08-10-2009, 09:24 PM
i thought it was my boat. but i just put up the pic to find out. it may have had a 302 in it i am not sure on that. the 2 owner of the boat is no longer with us. the drive was stolen and he had worked or changed the engine at that time.