New boater in need of some prop advice...

[AlwaysSmooth]

Hello! I'll start by saying I'm new to boating and new to the forum so greetings to all! Now to the fun stuff...
I have a 94 Ebbtide Campione 190. I just recently installed a new engine, so last night i finally got her to WOT. I was less than impressed. It has a 5.0 mercruiser, so I was expecting at least 45 MPH (with just me and one other passenger). The best I could reach was about 35 mph at 4800 rpm! The boat felt like it was stuck in the mud, and felt like it was struggling. I know that the prop that is on there is an aluminum 3 blade, 17 pitch. I have no hydrofoil or tabs. I would appreciate any suggestions on where to go with this, and thanks in advance for your help!

 

[steelespike]

Re: New boater in need of some prop advice...

Do you know the gear ratio? Was it originally a 5.0? My info says 1.50 or 1.65 ratio.Is your speed by gps?
Your ratio may be stamped on the outdrive.the Calculator says your slip is way high. 32% with a 1.50 and 25% with 1.65.
Normal is around 10%.You need to verify the tach and get a gps speed.Some cells have a gps app.
Do you trim up for best speed/rpm. Is there a whale tale on the outdrive?Is the motor broken in?
Does the boat respond to up trim and get up free of the water?

 

[AlwaysSmooth]

Re: New boater in need of some prop advice...

I'm not sure of the ratio. The 5.0 is the original motor (size) that was in this boat. I did not measure the speed by GPS but that's a great suggestion! What exactly is my "slip?" I am trimming up (about a quarter up) to get the best speed, and there is no whale tale on the out drive. It doesn't really have an issue plaining, and i trim it the highest I can before I start to hear that "prop hum." that seems to be the sweet spot where the most boat is out of the water. And I'm thinking the motor should be broken in, it's got about 10 hours or so on it.

 

[emoney]

Re: New boater in need of some prop advice...

Another thing to consider is there's always the possibility that your boat has had some water intrusion at it's age. Wet foam and rotted wood can add some serious payload. Why did you think 45mph, was that the speed before the motor swap? Are you sure it's firing on all cylinders? GPS it 1st and that way you'll know what you're getting.

 

[steelespike]

Re: New boater in need of some prop advice...

Slip is how they measure the actual forward movement through the water. ( a liquid)
Typical boat/motor combination has about 10% slip.could be less or a little more.
A 12" pitch theoretically moves one foot in one revolution At 10% slip that would be about 10.8 inches.1.2" less.
Pontoons and really heavy boats have higher slip numbers. pontoons have about 24% slip again some could be higher some lower.
Slip,cavitation and ventilation are not directly related." Cavitation" occurs in low pressure areas of a prop and can cause erosion in
those areas.Ventilation is when a prop gets air bound losing its grip on the water. From any number of reasons.Poor setup,poor prop design,improper operation etc,etc.