2005 Stratos 386 XF - 140 HP Suzuki

[Moonlighter]

I can't recall if you said your current prop is stainless or alloy ...

But as I mentioned earlier I run a Suzuki stainless 3 x 14 x 20" on my DF115, it's a very popular choice on the 115/140's and on my boat spins to around 6200rpm lightly loaded. Good grip, lift etc.

Did you end up lifting the motor as suggested? He anti-vent plate should be skimming the surface at mid-trim settings at a fast cruise speed.

[kwaskow]

I can't recall if you said your current prop is stainless or alloy ...

But as I mentioned earlier I run a Suzuki stainless 3 x 14 x 20" on my DF115, it's a very popular choice on the 115/140's and on my boat spins to around 6200rpm lightly loaded. Good grip, lift etc.

Did you end up lifting the motor as suggested? He anti-vent plate should be skimming the surface at mid-trim settings at a fast cruise speed.

I checked the vent plate at WOT and full trim...not mid-trim. Ooops. Do I need to make some more visual checks at mid trim and not WOT???

[Moonlighter]

Yes, you should check it at about 5000rpm and 60% trim, or thereabouts - this is the right way to check engine height. Should be skimming surface or getting splashed, but not under.

If you can already trim it out to max and not lose grip, then it's likely you can go up one hole at least.

WOT and trimmed out as far as possible is the way to check what max rpm you can get from the prop.

You should gain some rpm going up a hole. And get out of hole a little better.

Current prop - alloy or stainless?

[kwaskow]

I believe it is an alloy prop currently, but not sure how to tell for certain....?

[Moonlighter]

Most stainless props will be polished to almost mirror finish.

Ally props usually painted white, sometimes they are black. Some stainless props may be painted black too. Yamaha ones usually are.

If you take the prop off, stainless is clearly quite heavy, while alloy is light weight.

A stainless prop grips the water much better than an alloy prop and has less flex.

So seem likely that the Suzuki 3 x 14 x 20" stainless would be a good choice for you from what hove said.

But First, get the engine height sorted. I would suggest lift up one hole and test again with current prop. See what revs at WOT trimmed out as far as it will go without losing grip.

A really good idea in this whole scenario is to get onto a good smooth stretch of water, and with a helper:

1. record GPS speed from idle, every 500rpm, all the way to WOT.
2. Note the revs at which the boat gets into plane.
3. If you have the SmIs gauges or engine data on a MFD screen, also note fuel economy at each position too.
4. Do an "acceleration out of the hole" test: idle along just in gear, then, with a stopwatch, time how long it takes to get from idle revs to 5000rpm when you shove the throttle hard down. Set trim in mid position and keep it there between runs to make the comparison fair. Same load on boat.

If you do these tests, it gives you the base-line for comparison.

Then lift the engine height, and run all tests again, now you can measure the true differences.

Same when you change props.

The rule is: change one thing, measure again, then change next thing, measure again. You then get good data and will know for certain what you have gained or lost.

We run these tests in our fishing Club when testing and comparing props all the time. Whenever we get new members who don't know too much about props we get them to do this and before long they understand the value of data and end up making better prop decisions. Of course, it helps if you have a dealer that is willing to lend or exchange props with you until you are happy. We are lucky that we have a couple in our area who will do that.

Props from different manufacturers and models will perform very differently sometimes, some lift the stern, some don't so much. Some hold plane at low revs better, some have better top end.

You can match the characteristics you want better with the prop you select if you do the tests and keep the data. It is truly worth the effort.