Prop Question

[Night_Sailor]

I bought a Fisher 20 CC last year. This year I bit the bullet and followed the advice of many and bought a new ETEC. I chose the 150HP small block. I would have liked to go bigger but it seemed adequate for my needs and I also got a 7 year warranty on it.

My boat has a cut down transom and instead of putting on a 20" shaft outboard, I decided to use a jack plate and a 25" shaft. There won't be much adjust-ability because I'll be using 5" of the 5.5" vertical lift. This should also allow me to tilt the motor back as it is supposed to tilt. I bought the boat without a splash board, which I assume was tossed out because the existing motor interfered with it when tilted back.

My transom is solid, however, I'm worried the jack plate will add a lot of torque to the top of the transom. I plan to bolt a 3/8" thick aluminum plate across the transom for extra mechanical strength, and to minimize water intrusion.

So, the final decision I have to make is what size prop? Should I go stainless or aluminum? I have heard that I might get an extra 1 mph out of stainless. I'm open to suggestions and recommendations.

Also, what spares should I keep? Drain plug? Spare nut? Spare prop?

[THEFERMANATOR]

If you bought the engine new, then your dealer will set it up for you. That is a requirement per EVINRUDE is that all engines are setup by the dealer BEFORE they are registered and a warranty issued. EVINRUDE lost quite a few etecs early on because of improper setup(mostly propping), so they now require the engine to be setup by an authorized dealer. If you bought the engine used, then you need to be pretty critical with your propping of it. What kind of prop depends alot on the hull type and your useage of it.

[smokeonthewater]

ALSO the jack plate will add absolutely NO more force or stress to the transom.... The force comes from the prop and the mathematical lever arm is exactly from the prop to the top mounting holes in the transom and the fulcrum is the lowest contact point of the transom

You could have a 20" motor or a 120" motor w a 100" jack plate and the leverage would be the same

Now a 25" motor on a 25" transom on the other hand WOULD apply more leverage to the transom than your setup. ..
You are worried about a nonexistent issue.... Forget the reenforcement plate..... Instead just look at blocking water... MUCH less strength needed for that.... Plastic would be my choice

[Night_Sailor]

What about prop type?

Aluminum I'd stainless steel?

Spares?

[smokeonthewater]

Minimal difference in performance .... Stainless is tougher but aluminum is cheaper.

[tsubaki]

FERM and smoke do have valid points.

I normally carry one of the spare props I have tested previously, not to mention the stuff to install/replace it with, all the way down to the thrust washer.
The prop composition usually depends on your habits, I happen to like the stainless.

Other spares also depends on your habits. I usually keep a spare portable bilge pump with alligator clips and hose connected, spare drain plugs, fuses, oil, anchor/rope, one more safety vest and throwable than needed. If offshore fishing or camping or riding the grandkids around there will be other things added to the pile of stuff.

Depending on what your jack plate setback is and how you normally load the boat, you might need to raise the engine yet higher than a regular transom mount. A 5" setback might need to go up 1 or 2 bolt holes, a 10" might need to go up 2 or 4 bolt holes.

If you don't have a prop already, I'd expect to start out with about a 15x17" stainless and go from there. If the engine is setup correctly and depending on your habits you might need to go to a 15" or 19" and/or anything in between. This is where a dealer setup situation will save you time/money and get the best performance.