4 blade props on dual merc set up

[tmitchell5188]

I picked up a set of 2 4 blade SST props off of ebay. There are 4 rubber plugs on each prop. One is missing a plug. My old 3 blades don't have any plugs in them. Do I need to worry about the missing plug?

I was having problems getting my 25' walkaround up on plane with 2 175 HP merc carb'd 2 strokes. I also changed out the trim plates to larger ones on my trim tabs.

 

[Dhadley]

Re: 4 blade props on dual merc set up

They probably aren't SST (model) props. SST is a model of a 3 blade prop made by OMC / BRP. The holes & plugs you refer to are the vent system. If they're large, stepped holes that's probably the Mercury PVS system. You can buy plugs or plugs with smaller holes to fine tune the holeshot.

We don't have a lot to go on but generally speaking, when going from a 3 blade prop to a 4 blade of the basic same design you'll be able to raise the motors.

2 175's should do just fine on a 25' walkaround assuming they're running right and the boat is OK.

 

[tmitchell5188]

Re: 4 blade props on dual merc set up

Thanks. I guess I should of said that they are stainless props. What would be the advantage of raising the motor other than reduce lower unit drag? How would I know if raising it would help?

My goal is to get it in the water this weekend and try it. I think going from 3 blade to 4 blade should help. I also replaced my trim tab plates. I had 9"x12", and I went to 12"x12". Plus, the aluminum on the new plates is about 3X thicker than the old plates. I'm sure that I was getting some minor flexing of the plate. Heck, I could flex it a little with my 52 year old hands, so I'm sure the water pressure was cause some minor flex.

I'll post my results when I try it. BTW, the boat is stern heavy with the twin 175's, and a 190 gallon fuel tank near the back of the boat. The cuddy has a stand up head (enclosed), and a 9.5' beam, with a huge Carolina flare on the bow, so it really takes big waves good.