Gas Prop Pitch vs RPM

"Prop pitch? I have a Wellcra

"Prop pitch? I have a Wellcraft 2900 Express Cruiser with about an 11ft beam. Figure about 10,000 lbs. I have two brand new Carburetor Inboard Mercruiser 350’s, 8:1 compression with 1:1 transmissions. My ordeal is that I am trying to figure out my best fuel consumption with what I have. At 2500 rpm I cruise at 19 mph with about 1.3 miles per gallon, 6.6 gph per engine. I don’t think it is bad, but I think it could be better. Seems as though I have too much prop due to the fact that after 2800 rpm, I am into the 4-barrels and can barely get to 3000 rpm. I would like to know a ballpark figure of what my prop pitch would be and should be for this boat. I know I will be told to take it out of the water or something like that. I am open to suggestions. I know that as I operate at higher rpm’s, my fuel economy gets better. So I figure that I should maybe pitch down one or two degrees to get my fuel economy up past 1.5 to 2 miles per gallon at a higher rpm. What do you all think? What should my props be?

Lou"

"Lou, You are lugging the mot

"Lou, You are lugging the motor badly if your WOT only commands 3000 RPMs.

You obviously have either a prop problem or an engine problem.

What props are currently on the boat?
How did they get on there?
Why did you have to replace the motors?

You aren't even close with what you have. Assuming (which I have learned to never do) that the motors are running properly, they should acheive 4200-4400 at WOT. This would allow them to cruise nicely at 2800 without opening the secondaries. This will gain you some economy.

Let us know what props you have now and maybe someone here with a similar boat can help out with a recommendation.

Rick"

"Rick,

Thanks for the rapi

"Rick,

Thanks for the rapid response. I know I dont have an engine problem cause they are NEW. They were replaced cause they were raw water cooled. I needed freshwater for my use and experience. The props were on the boat when I purchased it. I dont know what props I have now. I was told that with these props, it is for fuel economy. BS I say cause I cannot hear the 4-barrels kick in. SO yeah it is bogged. I am looking for someone with a similar boat but is there someone out there??? I will be diving the boat when I am in clear open water again this coming weekend. Hopefully this will tell me alot more.

Lou"

"There should be something sta

"There should be something stamped on the props somewhere, typically around on the hub somewhere between two of the blades. Take a wire brush and a scouring pad in the water with you... hopefully you can find something resembling a size and pitch."

Is there anyone out there that

Is there anyone out there that has a similar vessel to me that may know the correct size of props? That way when I dive the boat I know what direction to go.

"Did you try contacting Wellcr

"Did you try contacting Wellcraft?
Also, their website has a forum and downloadable owner's maunals and brochures back to 1985. You might be able to find something there.
www.wellcraft.com
Click on the "Owner's" link."

"Warrent,

Thanks for the a

"Warrent,

Thanks for the advise on the website. Although I have been there many times, it still comes without results that I am looking for.

But in the meantime when I am underway in the Gulf, I do plan on diving the boat to see what I have.

Everyone else, I am still looking for someone who has similar vessel to me that could tell me what they have and how there fuel economy is as well. I feel that 1.3 (2.6 per engine) is good. However it could be better."

"Ok,

I took the pros off.

"Ok,

I took the pros off. They are 14X13. Just what Wellcraft put on the boat at the factory. They each had a little ding in them but I dont think it is enough to cause the boat to get higher rpm. I am thinkng that the pitch is still too much and that maybe they changed the transmissions from 1:1 to 2:1. I dont know. Bottom is clean, props are going to the shop today. Any suggestion on getting my rpms up past 3000 rpm and gaining my top speed???"

"Louis:
"New" only

"Louis:
"New" only means that you are the first owner.
If the boat was running correctly before the switch over, then the new engines should run the same as it did with the old engines; just better. Are you sure that the carburetor and throttle linkages for each engine are adjusted properly? Have the installer go back over the throttle cable adjustments again WTH A MANUAL as a guide. Guy"

Problem Solved. I had the pro

Problem Solved. I had the props tuned up. They were out of wack. The boat now does 30 mph at 3000 rpm in 5 foot seas. I put it to the test like we do in the NAVY. I spoke with my engine installer's (dad & I) and told them to make sure the carbs are adjusted properly. We both agreed that the "new" engines were not the problem. I am the first owner on those engines. Further discovery was the there was a mild growth of barnical scales on the shafts and struts when I had scraped them from before. All is good to go. I want to thank you all for your inputs. You have all been a great help. I plan on returning the favor as I read the posts! Take care and keep your boat SHIPSHAPE!!!