What propeller for a 23' Sceptre?

breadandbobbers · #1 07-22-2009, 07:19 PM

I have a 1978 23' Sceptre. I had a Armstrong bracket installed on the boat recently and put a brand new 225 hp Opti on it. The prop before did well with the boat, a 14P Mercury Mirage. However now the propeller seems to not have enough pitch and gives too much bow rise--before the boat had the bracket the boat was definitely bow heavy and the propeller did well, not it does not. The boat maxes out at 6400-6500 rpms currently, and max rev on the opti is 6750

anyways does anyone have a similar setup or have any recomendations? I use the boat for fishing offshore so I am looking for something that will perform well in the open water.

Fr. Frank · #2 07-24-2009, 12:56 AM

Bracketed motors tend to have more bow rise than transom motors. 6400 rpms is way too much for the 225 Optimax. I thought the factory rev limiter was supposed to cut in at 6300 rpms. Max rpm range for the 225 is 5000 - 5750 rpms, not 6750. Ask your dealer about that.

Since Mercury Marine doesn't list a 14" pitch Mirage Plus, I'm going to assume it was re-pitched down from a 16"P, which is the smallest I see in the catalog. If you're turning 6400, and want to get down to 5750 (max of max rpm range), I would estimate that you need an 18"P Mirage Plus prop.

breadandbobbers · #3 07-24-2009, 02:36 AM

sorry about my info, i was exhausted last night when I posted that info. Worked some long hours then had a frustrating test run with the boat. Anyways it is a 15 pitch mirage prop, turning 550 rpms. Sorry for the confusion

eggsuckindog · #4 07-24-2009, 02:56 AM

Quote:

sorry about my info, i was exhausted last night when I posted that info. Worked some long hours then had a frustrating test run with the boat. Anyways it is a 15 pitch mirage prop, turning 550 rpms. Sorry for the confusion

doesn't seem possible either

Fr. Frank · #5 07-24-2009, 09:20 AM

If I assume that when you said 550 rpms, you actually meant 5500 rpms, then you should be right on.

5500 rpms, with a 1.75:1 gear ratio, turning a 15" pitch prop, assuming slip ratio between .10 and .14 , works out to a top speed of about 38-40 mph, which is pretty good for a 23' Seacraft with a single 225.

My 23' Tsunami with a single Johnson 225 turned 5900 rpms with a 17" pitch prop behind a 1.85:1 gear case, and topped out at 39-40 mph. But I hardly ever went above 28-30 mph.

With a bracket, I strongly suggest you need trim tabs, and someone to teach you how to use them properly if you don't already have that skill.