Should I go one pitch larger?

Hello,

I have a 1995 Sea Ray Signature 200 cuddy. It has a Mercrusier 5.0 (2bbl 190 HP) and Alpha 1 outdrive. The boat weighs about 2900 lbs and I think the prop that I just had my mechanic put on is a 14.5 x 21 pitch. I had him put on a prop with more pitch because the old SS one was bent and I was also over revving. From my understanding the WOT RPM is about 4300-4600 RPM for my boat.

I just took the boat out today for a test of my new prop. The lake was nearly glass so it was very smooth (no wind). I took the boat both up and down the lake to take the current into account, but both runs were the same.

I ran a top speed of 48 MPH on the GPS at 4700 RPM trimmed almost all the way out. So my question is, should I go to a 22 pitch (one size larger)? I heard that every pitch size changes RPM by about 200 RPM, so I am thinking that would put me in the correct RPM range. Would going 1 size larger increase speed slightly? I am thinking if the engine has the power, it should be able to? Is 48 MPH fast, or about normal?

I am looking for speed and understand that I will lose some acceleration by doing so. When I tested the boat it was just me and my gear on board and a half tank of gas. I know if I put more people on I would slow down, but am I doing it correctly? Do you want to test props fully loaded, or the way I did it?

I feel like I'm right at the limit, and Im not sure what to do.

Thanks,

Matt

Re: Should I go one pitch larger?

4700 seems like a solid WOT rpm. I wouldn't run my boat that fast for long, but it's a decent redline for a small block chevy. IMHO I wouldn't prop any bigger, you'll lose too much on the hole shot. It's no fun making everybody scoot to the bow to get on plane.

Re: Should I go one pitch larger?

Did a little checking on the max rom rating.. check this link and confirm if it's also your engine: http://www.perfprotech.com/store/articles/mercruiser-50l-engine-specifications.aspx You are in the sweet spot, so no need to change a thing.

Re: Should I go one pitch larger?

briggs09hp said:

Would going 1 size larger increase speed slightly?
I am looking for speed and understand that I will lose some acceleration by doing so.
Do you want to test props fully loaded, or the way I did it?

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From where you, are any increase in speed will imperceptible even if it can be measured by GPS.
Loss in acceleration is generally much easier to notice.
I think it makes more sense to test with a typical load and typical conditions.
I wouldn't go up but I guess it all depends on what you want. I'm propped to over rev if wide open with a light load, so I don't go wide open with a light load. When I do carry a capacity load the acceleration is still acceptable. My preference is to be a tad slower on the GPS when I'm alone as opposed to being an obvious slug with a boat load of friends and family.
I'd load her up to capacity and go for a spin. See how she works just for reference sake.
You probably have more than enough pitch. IMO

Re: Should I go one pitch larger?

Leave it. You're good. I believe you will regret going to a larger pitch and wouldn't gain any speed. And I wouldn't even bother to be careful with light loads because occasional blasts of 4,700 rpm will never harm that motor or outdrive...it's far from an "overrev" situation, and being a hair above your range will really benefit you in daily cruising and holeshot. And when you add a little chop and a little more weight, you'll be absolutely perfect. IMO 48 mph is pretty good speed for a boat of that age/motor/design/size.