prop. recommendations

[onesubdrvr]

Another question,

On the Ragazza, 4.3l, 3100lb boat, 190hp, OMC Cobra outdrive (I think I covered the essentials), the current prop is a 15x17, is that a good size, or should I go smaller with more pitch? maybe a quick lesson in prop selection? I know that more pitch = less RPM / Etc., but does bigger, less pitch = more top end?

Wayne

[Morgan's Cloud]

Wayne ,

What is your current prop ... manufacturer/'model' ?
Top rpm s and speed ?

You may already have the ideal prop and not know it ...

Steve

[onesubdrvr]

Well, I was afraid that someone was going to ask that. The prop is a "Viper" 541 pt#174889. That is all I know. I bought the boat a few months ago, and have been tinkering with some things on it, so I've never had it in the water to have any performance specs to give you. It has some damage on the trailing edge, and now the boat is ready for the water, but I don't want to run it with a damaged prop.

Wayne

[Tomahawk]

Good idea to take your prop to a prop shop to have it repaired. Then take it out and see what top rpm and speed you get. Also, note your impressions of acceleration and if there is any undue vibration.Then, provide that information here for feedback.

[onesubdrvr]

Well,

Finally got the boat out on the water, unfortunately as of yet, haven't taken to a place without posted speed limits (intracoastal boating here in Port St. Lucie, current speeds limited to 30). But, at 3800 rpm, was getting about 35-40 mph, played with trim a little bit, RPM's seemed to perk up, but then, out of water way, down to minimum wake zone. Anyway, seemed that at low RPM's, acceleration was very slow, I mean I didn't slam down the throttle yet to see exactly how quick to get on plane, just seemed a little slow.

Any way, does any one have any ideas on what size prop is typically run on this type of boat with the 4.3l Cobra out drive? Maybe starting from there then tweaking will be better.

PS, how accurate are the old pitot tube speedo's anyway, I think I will replace mine soon, the pick-up tube is broke, will that affect the reading (it didn't even deflect until about 20 MPH)

Thanks!
Wayne

[MOP]

What prop is on it now? Was 3,800 the tops you could turn? Gut would be 2" less pitch, try to get into the mid 4's under 4 you are lugging it. With just you and full fuel I like to see 44-4600 that will give you a little extra for passengers.

P.S. P tubes suck get hold of a cheap GPS!

Phil

[onesubdrvr]

What prop is on it now? Was 3,800 the tops you could turn? Gut would be 2" less pitch, try to get into the mid 4's under 4 you are lugging it. With just you and full fuel I like to see 44-4600 that will give you a little extra for passengers.

P.S. P tubes suck get hold of a cheap GPS!

PhilCurrent prop is a 15x17

I had been thinking about going GPS Speedo, I guess my decision is made. As far as RPM, I'm gonna have to take it back out this weekend to check max RPM's, but am going to have to find a place where there is a long enough run that is not speed restricted to get it up to full speed, will post again after that.

Thanks
Wayne

[Fish boy]

Current prop is a 15x17

I had been thinking about going GPS Speedo, I guess my decision is made. As far as RPM, I'm gonna have to take it back out this weekend to check max RPM's, but am going to have to find a place where there is a long enough run that is not speed restricted to get it up to full speed, will post again after that.

Thanks
Wayne

GPS speedos are really nice but pricey for your application. You might be better off buying a handhled gps with mapping for less money than the gps speedo and you will still get the accuracy of the gps speed and never get lost to boot. Many have upgraded features (garmin blue charts for one) that will tell depth, reefs, marinas...etc too. A little mor ebang for the buck IMHO than gps speedo.

if you can narrow it down to 35 or 40 it will be helpful in prop selection, and WOT rpms will also be helpful. Sorry I do not have an answer for what is normally run on your boat, but might be able to help with: gear ratio; rpms, size prop currently on; and max speed.

Also might want to check your fuel level and test at an amount you will use the most. For example, my boat holds 100gal. if full, that is approx 700lbs extra in my boat. I turn 200-300 less rpms with my current setup with a full tank. I usually run it 1/2 or less so I proped for max rpms there. Still works with full tank, but runs better when some of the fuel burns off.

[mikev]

my regazza is a 19' with the 4.3 but its a merc. i ran a 19" prop with the 2 bbl carb and could turn 4800 rpms. after i went with an aftermarket intake and 4bb carb i was turning 5200 rpms so i had the prop repitched and lab finnished now I can run 4900 rpms and about 50mph

[onesubdrvr]

Well

This weekend will be a better test of speed and RPM's. I had the wife and all the kids with me this last weekend and get nervous that one of the little munchkins is gonna bounce out, so I'm perhaps overly carful with 'em on board. So Saturday or Sunday I'll just take my buddy out and spend the morning zipping around adjusting trim / etc. until I get max RPM's, and Speed. (I'll try to pick up the Garmin before then), Then I'll fire you awesome individuals the numbers and go from there.

Thanks
Wayne