Avanti 3258 Prop Size???-gctid811378

[KidsTuition]

Ok crew all of you have been a great help with this project we call a boat! We are getting closer and closer every day!! Having a hard time locating the recommended Prop size for this boat. Any help or experiences?? 4 Blade or 3 Blade?? Took boat out for the first time over the weekend and neither motor would spin over 3k rpms. Have a vibration at 2300 rpms which I am hoping will go away with new props as well. I am not sure of the prop size that is on this boat... I am going to borrow what I believe to be 21 pitch props to see if that changes anything. Thanks as always for the help!!

[mister_larry]

As a place to research you might see if the local library has a copy of David Gerr's "Propeller Handbook" It's a great resource. There are a lot of questions that go into getting the "correct" prop answer.

The naval architect had some specifics in mind when the hull was designed and then the engines chosen and the props installed. Since then what has happened? Some engines are designed to turn at 3000 RPM. Some boats need 4 bladed props because a three blade tip gets too close to the hull. Some planing attitudes dictate specific pitch. See the theme here? You need the answers to many of the questions raised in his book.

Then a good prop shop can give you what you need.

[Ruffryder]

3258 B2 originally came with 18.25 X 19P I believe.

Many will down pitch it to 17P.

[KidsTuition]

It appears that Bravo Two Aluminum (18 3/4 x 17") MERCURY LH Propeller, would be the next pitch size option. Would changing the diameter to 18 3/4 cause any issues that you can think of?

Ordering props today but torn between the pitch drop and diameter option. Thanks as always for your help.

[Ruffryder]

Anytime Josh.

What size prop on her currently ,

No half an inch in diameter shouldn't make that big of a difference.

Perhaps verify both tachs are on the money with a correct shop tach

[KidsTuition]

Here is the situation... The boat has to be pulled out of the water to remove the props to take them to the closest prop shop. I was hoping to order props without pulling the props to keep from having to pay the fee to pull the boat out and stored until new props arrive or hire a diver, since I can take the boat to a local sandbar we all hang at and replace them there. The plan was to order factory replacement size props then take the old props to the prop shop and have them reshaped to a different size for back ups pending which size prop worked better. It appears now we have a lower unit debate, they look to be alpha 1 gen 2s but online is showing bravo 2. I have a few pictures of the lower units when the boat was out of the water. The lovely mechanic that is NO LONGER the mechanic was suppose to gather all the answers to these questions before he put the boat back into the water as well as replace the props. Now we are doing all the work our selves to assure that the work is done correctly even if we have to figure it out as we go with the help of the bayliner family here on the this forum. As always I thank all of you for your help!! I do like the idea of a shop tach may try that this weekend! One thing about this journey, we are going from know little to nothing about these type boats to learning a lot!! As always stay safe and keep floating friends!!

[KidsTuition]

Pic of the lower units

[KidsTuition]

lower unit pic


Attached files

[KidsTuition]

Anybody heard of or has any experience with a BIG COW 4 Blade Prop?? Cant seem to find anything good or bad on these.

[Ruffryder]

Probably the best prop for your outdrive B2...

Not cheap

[KidsTuition]

Gave them a call... looks like I will be pulling my old props first. To much money to guess whats currently on there to compare rpm at wot.