1990 wellcraft 186 eclipse 4.3 L mercruiser alpha 1 question about prop.

[starwriter]

I have a 18.6 ft.boat with a 4.3 liter mercuiser alpha 1.Right now I have a Michigan 3 blade, 14 dia.,19 pitch aluminum prop.
I found a used but, in nice condition,QuickSilver stainless steel 3 blade,14 dia.,15 pitch prop.Came off of a 4.3 Liter Mercruiser 26 ft boat.
What results will I have from changing from a 19 pitch to a 15 pitch prop?Will I gain or lose speed?

My thinking is,If this 15 pitch could push a 26 ft boat.Then,it should have no problems pushing a 18 ft boat.as should go faster.using less rpms.
17-21'ft - (33-42 mph) 14 R 19 3
over a ,
21-26' ft- (18-31 mph) 14 R 15 3
I'm open for thought's?

 

[Scott Danforth]

Re: 1990 wellcraft 186 eclipse 4.3 L mercruiser alpha 1 question about prop.

you will over-rev your boat and it will go slower on the top end by going from 19pitch to 15 pitch. It will however give you a much greater holeshot

less pitch, means less forward thrust per revolution.

 

[coopin87]

Re: 1990 wellcraft 186 eclipse 4.3 L mercruiser alpha 1 question about prop.

Bigger pitch prop faster top speed (if the boat can push it)
Each pitch you go up drops your rpms about 150-200 give or take

What you need to do is give this information
WOT speed (from GPS)
WOT RPM's (needs to be accurate)
Your outdrive gear ratio

The guys here can plug the numbers into a calculator and let you know what your best bet is.

I would say no to the 15 pitch prop unless your rpm's are low with the 19

 

[starwriter]

Re: 1990 wellcraft 186 eclipse 4.3 L mercruiser alpha 1 question about prop.

My rpms are high with this 19 pitch prop.Last I checked.I was full throutled out at 31 mph at 60 rpms.
Your saying if I install this 15 pitch prop I'll be higher rpms & lower speed?
If this is the case,sounds like I just need to go from a 19 pitch to a 20-21 pitch.

 

[coopin87]

Re: 1990 wellcraft 186 eclipse 4.3 L mercruiser alpha 1 question about prop.

Yup ... no need to go down ... If it were me I would go to a 21 SS Im not positive on what your WOT rpms should be but I think 6000 is high. I was worried about mine at 5500 rpms. Reproped and brought it down to just over the recomended WOT rating and increased speed drastically.

IMO dont waist your money on the 15 pitch prop unless you plan to resell it