Need some prop advice

[Frank15028]

Ok I need a little help with a prop problem.

I recently purchased a 2000 regal 2150LSC.
The boat has a 5.0L mercruiser engine with a Alpha drive. The boat came with a 21 pitch 3 blade aluminum prop with 14 diameter. The boat runs fine with two adults in it. However with 4 adults it takes forever to get up on plane. Quicker if people move to the front of the boat. Max rpm is 4800 and I can stay on plane at 3200 rpm.

I spoke to my local marine mechanic and he suggested a 4 blade to help pop out of the water quicker. He sold me a Quicksilver Nemesis 4 blade aluminum Prop 21 pitch with a 14 inch diameter. We tried it out today and it was way worse out of the hole. It would just plow through the water with a max rpm of 2600 rpm and would not pop up on its own. Once people moved to the front of the boat it would slowly get up on plane and reach a max rpm of approx 4600rpm and would stay on plane at 3000 rpm.

Im not looking for top end. I just want to be able to get on plane without having everyone move to the front of the boat. Wondering if I should switch to a 19 pitch four blade? Any advice would be great. I do boat in georgian bay (lots of rocks). So I dont really want to go with a stainless steel prop.

Thanks in advance..

 

[alldodge]

Howdy
Not much of a marine Mech if he offered that
Need to add 2 inches of pitch going from 3 blade to 4 blade. A 4 blade 21 is like a 3 blade 23 pitch. So you went up in pitch.

The 4 blade also increases lift so if it actually worked, it would lift the stern and then the prop may ventilate.

I would suggest sticking with 3 blade and go with a 19 and if you can get a 14.25 diameter would be good

 

[QBhoy]

Yeah agree with the above really. Just watch the rpms at the top. As much as I’m not a fan of the high 5 prop...it might just do what you want out the boat. As in a 21” high 5. Should give much better acceleration and only a little loss in top end over a 21” ally 3 blade.
mother option would be a 19” tempest plus. They can act like an inch larger pitch but actually drop rpm over a 4 blade of two inches more pitch. And see more speed and lift.
just the other week a friend got a regal 1900 with a 4.3 mpi. It came with a 4 blade 21”. It hit the limiter with half tank and 3 up at 4950 rpm and 46ish mph. We put my 19” tempest plus 3 blade on it to try. We were amazed to see the bigger prop but less pitch see the boat run at 4850 rpm aired out and about 53 mph gps without trying. That threw the general rules right out the window. Amazing prop on that boat and many like it.