Upgraded to a 383 stroker on my fiesta vee 250. What about the prop?

ioannis13 · March 2021

Hi all, I am new in the forum. I own a fiesta vee 250 2003. I decided to replace my engine to a reman 383 mercruiser , from a 350 mpi . I have a bravo 3 sterndrive with duoprop 20 inch.

I used to run at 3500 rpm/m at around 19-20 knots (tabs up), which I think is too slow. Should I go for 22" pitch props?
I also have a outdrive engine (15 ps) on my platform due to the fact it's an obligation in Greece to boat with 2 engines at least, Mediterranean sea ain't a lake.

Would you increase the pitch of your prop if you were me?

Handymans342 · March 2021

Was 3500 at full throttle?? If so then yes go to 22 or 24

ioannis13 · March 2021

hi there, no I meant that once in plane, the speed was at 3500rpms at 20 knots. WOT I was at 5300 and 32 knots (like 36miles)

LaRea · March 2021

Welcome to the forum. That's interesting about having two engines, but it makes complete sense to me. And yes, cruising at 20 kts seems too slow for your boat!

For your new engine, what is the recommended max RPM (red-line RPM)? I'd guess probably around 5000 RPM.

Most people size the props so that the engine hits red-line at wide-open throttle (WOT). If your new engine gets to 5000 RPM before WOT, your props need more pitch. Typically you would get around 200 RPM for each inch of pitch.

ioannis13 · March 2021

Hi LaRea, thank you for your reply and welcoming me to the forum. Indeed, I will get a pair of 22's and 24's with me and will go check. The 383 is given between 4800-5000 as max Rpm, indeed.

However does the "ratio" of my sterndrive Bravo3 has any role? has this anything to do with choosing the proper prop pitch?

ps: I am really happy that I discovered this forum, seems I can find everything I look for in here

Dream_Inn · March 2021

The ratio certainly has a role in getting to those RPMs, but honestly you just need to look at your max RPMs. As LaRea stated, every 200 RPM is an inch of pitch. You definitely need to go up in pitch. I'd go up 2.

We all would love to see some pictures of your boating area. I'm sure it's beautiful!

LaRea · March 2021

If the front and rear props are both 3-blade props, make sure to align them to each other for best performance.

https://rinkerboats.vanillacommunities.com/discussion/comment/132494#Comment_132494

ioannis13 · March 2021

@Dream_Inn thanx for the advice. I will post pictures and videos from Greek islands I visit with my boat sure, hope you will like them.

@LaRea
really helpful the propellers alignment graph, I will check if mine are set up as they should be

LaRea · March 2021

Yes, post some pix! Also a pic of your outboard setup. I have seen the Mediterranean Sea when she's in an angry mood, and it's no joke!

hooky13 · April 2021

hi all, there is a video filmed with a gopro9 black, yesterday in southern Athens Greece. you can see the small suzuki outboard installed in the rear of the boat. I kept the 20 pitch propelers not to push the new engine much, I will install 22''s next month.

The rpm smartcraft gauge doesn't seem to work properly, dont know if its a permanent problem or it's something I can fix (a friend told me there is a small switch behind the gauge to select the engine).