Mystery prop!

[Dja4260]

Hello everyone!

While new to this forum, I've been around boats my whole life. Growing up (in order of ownership) on a 23 chaparral, 19 ft Taylor, 19ft eliminator, 16ft Texas Tunnel Drag boat, 18ft Deaver Drag hydro (160 mph @ 7:85et 1/4 mile), to a 1988 180 Classic Wellcraft...

the 1988 180 Classic Wellcraft is in great shape, with a strong running Merc 3.0 w/ an Alpha 1 drive.

The current 3 blade Aluminum prop isn't perfect, has rash along the edges, and has NO casting numbers or anything to indicate pitch.

I cannot verify accuracy of the dash gauges, but they tell me

39-40 mph @ 4600 rpm. The boat planes decently quick and I cruise about 24 mph @ 3300 rpm. If feel that I have some a few hundred RPM still in it but don't want to overrev senselesly. Internet tells me the boat weighs 2100lbs dry. At mininum I have two adults, two small kids, and maximum load is 4 adults, 4 kids....

My end goal is to have more top end/cruising ability.


I suppose I'd like some feedback on similar boat setups and what props you've had success with.

Thank you,

 

[QBhoy]

I’m afraid you are going to have to open it right up to see what it does full throttle. Then you can look at what prop you need.
If you can’t see what prop numbers are. Have a really good look and clean between the blades. If not there, it will almost always be stamped on the hub behind the nut and locking washer that secures the prop.
Im guessing you will likely have a 21” or 19” from the numbers you have and knowing what 4 or 5 similar boats are like in my marina.

 

[Luke Brouwer]

I am 3 blade propeller fan.I bought 13.25 x 17 pitch prop on hexautoparts this spring,got me back on the water and it makes my boat faster.It's aluminum prop ,so much cheaper than OEM.My outboard is my 2001 Mercury 90HP 2 stroke saltwater.

 

[jimmbo]

Your engine's WOT RPM range is 4200 - 4600, so you don't have any more rpms. If you still have unused throttle, then you could add some pitch. If you are at WOT, adding pitch will drop the rpms, kill the holeshot, and usually be the same top speed +/- 1 mph. Lowering pitch will overrev the engine, provide a quicker holehot, and probably a drop in top speed

 

[TunaFish389]

I agree with the above, your got about everything there is from that motor. 40 mph GPS is respectable for a 3.0. I would guess your at 21p that will give you 13% slip, a new prop might give you a less slip and maybe a little more up top.

 

[Sea Rider]

Make 2 independent wot runs, one at min load, other at max load and report both wot rpm achieved at max throttle to see the rpm difference between both boating scenarios and how load affects increasing, decreasing wot rpm. Variable load is a serious wot rpm killer.

Happy Boating

 

[Dja4260]

Thank you for the advice.

The existing prop is a 14x19 Black Max prop. My father has a 14x17 brand new S.S that I'm going to try as well. If that works well, I'll have the Black Max repaired/cleaned up to be kept as a spare...

 

[Scott Danforth]

my ole 3.0 liter would hit 41mph with only me and a buddy on board with a 19p, (also kept a 17p and 15p on board for general boating and watersports)

unfortunately the 3.0 is not a power house.

 

[TunaFish389]

The 17p is not going to help your goals here. Your mph is likely off too. With the 19p you would be a 7% slip which is doable but considering year of hull and said condition of prop more unlikely to happen.

Going up on pitch will get you closer to your goal as long as in engine rpm range.