Too Big a Prop

[BillM2]

I've got an Alpha One on a 4.3L 21 foot Sea Ray and have switched to a Merc, three-bladed 14.25/21 prop and have noticed an great deal of improvement in top end speed. I can cruise now at 30mph at around 3200 rpms and have topped out at 41mph WOT (as measured by GPS). Wondering if there's any drawback with using this prop. The size shows up as recommended in most of the reference charts I've found.

Thanks!

 

[Tail_Gunner]

Re: Too Big a Prop

Your rpm's are the last equation, what are they running @ wot, that determine's engine health........

 

[sweebs]

Re: Too Big a Prop

ditto on the rpms, my experience shows that rpms AND top speed will be noticeably reduced if you're "over-propped" - I went from a 15 x 17 SS, busted it up, repaired and repitched to 19" ran way better. Tried a 15 x 19 composite, ran good but 5 mph slower. Tried a 14 x 21 composite and WOT rpms were down by 1000 and top speed was down by 10 mph! my 1991 175 hp 4.3 just couldn't swing it (the 21")

enough experimentation and you will find you sweet spot. good luck