re-worked prop...will it affect performance

[PDW911]

Instinct tells me yes.....my prop (aluminum) has been re-worked twice in last two years and prop is about 5 years old...I just re-powered my boat (1999 Trophy 2350 WA-23.5 ft with 5.8L Mercruiser 357 Alpha 4V (275 Crankshaft HP)-Alpha drive)

My WOT RPM is excessive 5400 vs the 4800 max spec (burped it to check) and I don't have the top speed I used to have (I haven't pushed it as the engine is in break in)....I think when I was out last week end I was only getting 20 knots at 3800RPM......the original boat specs showed their tests 40 MPH at 4500 RPM 5.7L 250 HP OEM engine with a 15" 17P prop...I never quite ever hit 40 MPH but I was definitely in the mid - higher 30's depending on weight loading and conditions

I believe my prop is 15-17, so would it make sense to re-prop?? With same specified diameter and pitch?? (I DON'T think I'm slipping, but I'll re-do the hub anyway...I don't know how to check for slipping)

We use boat salt water- off shore/near shore fishing and bay...occasionally tubing with grand kids...so I don't need pitch for water ski etc...just good overall performance

Before any one offers , I have to use aluminum....we used stainless and I went through two lower units due to severe pitting/corrosion (even with Merc cathode system...even Mercury was stumped)...something environmental in our neighborhood...we are thinking.... the utility lines are all below grade (at a shore town...doesn't make sense, but that is what we have), and there must be "leakage"...any way since we switched back to aluminum and watch our anodes we haven't had any issues for years

Thanks

 

[jimmbo]

If you're worried about the prop, just replace it. Alunimium props are inexpensive

 

[PDW911]

Am planning to do so...just wondered how many "lives" a re-worked prop has ..going out of spec with RPM's leads me to believe the pitch may have dropped or it wasn't re-worked properly....I'll have to play with pitch to see if re-powering had any affect with the OEM prop spec (15" d- p17).....I'm guessing not

Is there that much difference in prop mfg??...obviously Merc has their two aluminum offerings (Black Max and Black Diamond) but I see there are units from Solas, Michigan and Turning Point...all have similar spec props 14.75-15" 17P)...some with HUBS... some integral

 

[Scott Danforth]

there are good prop shops and not so good ones. I have had my VP props done about 4 times so far. each time, no affect on performance from new.

 

[ziggy]

going out of spec with RPM's leads me to believe the pitch may have dropped or it wasn't re-worked properly....I'll have to play with pitch to see if re-powering had any affect with the OEM prop spec (15" d- p17).....I'm guessing not

i had similar issues after a prop job. but i lost 400rpm. the only way i could think of to confirm that it was the prop was to get a brand new one that was exactly the same as i had. 19p black max aluminum. the new prop confirmed what i suspected. i got my 400 rpms back w/o doing anything other than switching to the new exact same number prop. so yes. reworked props can be done wrong. the wild card for you is your extra hp from your new engine. only way i can think of to know is to R&R w/same new prop. if rpms are to high, you'll have to go up to the next pitch to bring them down again. which imho would be good. your new engine with more hp was a winner.....
fwiw. i whined to my prop shop about them 400rpms and they redid the prop job a second time for free. i've still not put that prop on to see how it performs yet. i'm happy with the new one. the rebuilt one is my spare now. as long as it move my boat if i have to R&R in the water, i'll be happy....