Prop Question
 

My buddy just bought a 22ft Clearwater center console with a 150hp Yamaha 4-stroke. Its a heavy boat and comes with a "stainless" 19 pitch prop. Sluggish out of the hole and you have to ease the throttle up or it will bust out. Top end with the 19 p prop and light load is about 41 ish.

Here's one of my questions. The prop is said to be stainless, however it is painted black and a magnet will stick to it....so is it really stainless?

Another question, 2-stroke vs. 4-stroke - are the props interchangeable? The reason I ask is my buddy wants to try a 17 pitch prop to see what it does to his holeshot and overall numbers so I was thinking we could put my prop on his to see how it does. I have a newer Yamaha 150 2-stroke.

Thanks!
Blue

Yep, Yam paints some of their stainless props black. There must be just enough iron in the alloy to allow the mag to stick. If it were an Alum prop there is no way the mag would attach. Both those yams should share the same propshaft, but thats a big guess on my part. Look in an overtons catalog or any website selling props and see if they list the same part number for both engines?

Thanks Slot. I have heard of painted stainless props before. I guess its cheaper to paint than polish.

He put one of those hydrofoils on this past weekend and said it does much better keeping the bow down out of the hole. The hull is much better suited for a 200hp but he didn't want to spend an extra $5k. We are going to try it out this weekend weather permitting.

All my Yamaha props have been regular painted steel. Not stainless or aluminum.

Thanks for throwing in your .02 Chum. My buddy was going to call the factory first then give the dealership a good tail chewing if its not stainless since they advertised it as such.

Depending on the grade of stainless, there will be rust and magnetism.
Stainless, dosen't mean "it won't rust", it just stains less.
The higher the carbon content the stronger the metal, the more magnetic but the quicker it will rust or stain.
Almost pure stainless is too soft for most applications.

that thing needs to turn close to 6000 rpm at WOT, see what it will turn with the 19 at WOT, then change props accordingly

The Yamaha Tech line told me that the one like you are describing are called "Black Steel" which have "SOME"" stainless in them. They paint the prop to keep them from rusting, but we all know what happens when the paint wears off. Yamaha polished stainless props cost the same so I don't know why the dealer chose the Black Steel. Also the F-150 (4 stroke) has a v-6 gearcase so yes the prop from the 200 will work. Your friend might want to look for the biggest diameter that he can get to help prevent blow outs.

when it comes to stainless, unless you get into the 500 grade (anything less such as 300 ss) then a magnet will stick to it. Most items that are identified as stainless steel is only about 300 grade.

I have the chemicals to do a acid spot test and I can compare it to different test strips to determine what grade stainless it is.

thats the nature of the 4-stroke. what are your rpm's trimmed out and running with a normal fishing load. that will help determine what pitch you need.