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Hello everyone,

I've done an extensive amount of research and tried a few different props but I still have a feeling I don't have the correct prop on the boat... or something else isn't setup correctly. Maybe I should start by asking what speed I should expect to see from a 1991 Outrage 17, repowered with a 2018 Suzuki DF90A? I understand that the real question is more about what prop allows the boat to run at WOT when trimmed. But depending on what prop I've tried, the top speed I'm seeing with around half a tank of gas, my 220 pounds and virtually no other weight on board, is just below 30 knots... this can't be right, can it?!

Now I'll go into a little more detail. It's my FIL's boat that I don't have a lot of history with. He repowered it with a brand new DF90A in Spring/Summer 2019. A dealership installed the motor with a 13 1/4" diameter x 21 pitch, 3 blade, aluminum, Turning Point prop. We used it all last season in a wide range of conditions with the boat loaded, unloaded, fuel topped off, fuel near empty, and every configuration in between. The best top speed we were able to reach was just over 30 knots, at about 5500 rpm. The WOT range is 5300 to 6300, so you can imagine, after loading the boat for a day on the water, WOT is below 5300. After doing a lot of research, it seems that the DF90A is actually supposed to have a 13 3/4" diameter prop. I knew that would only add surface area, giving the prop more "bite" and bring the WOT number down even further, but I wanted to at least have a prop with the diameter that's spec'd for that engine. So after a lot more research I decided on two things. 1. Raise the motor two holes, so now the ventilation plate is about 1.5" above the bottom of the hull. And 2. I bought a Suzuki, aluminum, 3 blade 23p prop. I won't go into the amount of calculation involved in making that decision, but I'm guessing at least a few of you have been through it yourselves. And yes, I should have only changed one parameter at a time but I got impatient. Anyway, it worked! ...sorta... Top speed rose by at least 4 or 5 knots in comparable conditions to the original tests and with just two people on the boat I was able to sustain 35 knots! Unfortunately, holeshot suffered BIGTIME, and WOT dropped slightly to about 5300, which obviously would be below optimal once the boat's loaded. So on a recommendation from a friend, I decided to try a Solas 4 bladed prop. I agonized for a while about what pitch to go with and finally decided because of the added resistance of 4 blades instead of 3, I'd drop down to a 19P. Lightly loaded, WOT is now around 5800, which is the best it's been. The problem is top speed won't go above 28 knots! Also, I read while considering the 4 blade that they produce more stern lift which I can definitely confirm! In fact, I think it may be too much for a relatively light boat like the Outrage. The upside is that she jumps up on plane instantly! But the downside is, there's definitely not as much available trim now. When trimmed for flat, smooth water, crossing the wake from another boat or anything more than a very gradual turn, will cause it to ventilate. Also, with it on plane and trimmed the best I can, I looked over the back of the boat and I could see the ventilation plate is above water. Luckily not enough to expose the water intake holes but I don't want to take that chance.

So, a couple questions. Do I...
1. Leave the 4 blade prop on because WOT is where it's supposed to be, and lower the motor one or two holes to counteract the stern lift?
2. Leave the motor where it is and go with a 21P prop that's the correct diameter, jnstead of the undersized prop the dealer installed?
3. Side question - Could I expect noticable difference in performance between an OEM Suzuki prop and the aftermarkets? (Turning Point, Solas, Polastorm, etc)

Ultimately, I guess I'm back to my original question... What top speed should I expect at WOT? Maybe the whole problem is my expectations are too high.

If I'm completely missing something please let me know.

Thanks in advance!
Jason

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I have owned Outrage 17's since 2007.

Rather than explain why each of your attempts did not get you the performance needed, I will cut to the chase.

I just helped an Outrage 17 owner in DE rig his DF90A this spring.
Engine should be mounted with 2 empty holes above the top bolt.

As for prop, make and model of prop and gearcase determine diameter.

There are several make/model of props that will work. 3 bladed unless you are consistently pulling a tube or need a low planing speed rather than top end.

The two owners that I have talked with who repowered with a DF90A are running 14x18 Suzuki SS 3 bladed prop. If you need to go 4 blade, drop to a 16" in the same make of Suzuki prop.

If you change to another brand or model of prop, sizes above will not be correct since prop size is not universal across brands or even models.

With a light load, solo to hit 40-43 mph at 6200 rpm's. 2-3 people and gear expect 5700 and 36 mph.

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I was thinking the same thing Phil...3 blade SS 18" pitch.

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Awesome guys! Thanks for the input!

I'm glad to hear at least I got the motor height correct. After that, changing props is easy, haha! Now the only problem is convincing my FIL to go with a stainless prop. He's been a waterman most of his life (he's 74), and he's pretty dead set that if you happen to hit something with SS, there's a greater chance of damaging the motor because they don't have as much "give" as aluminum. If I understand correctly, this may have been the case in the past, with props that didn't have a rubber insert hub. But with a rubber hub, is there still a higher risk of damage with SS? If I can't convince him, what would be the best option in aluminum? I haven't seen aluminum props in even pitch sizes like 18. And I don't think I've seen 14" diameter in aluminum either. So if all I can find is 13.75, would a 19P be the right pitch?

Thanks again,
Jason

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Jason -

Blade design is different on every make/model of prop. Each prop performs a bit different so size is not transferable. I know, it is really complicated.

The prop recommendations I post come from owners who tested props on with the exact engine and whaler model and reported results.

I don't have anyone who has tested aluminum props on a DF90A mounted on any whaler model. Everyone has gone stainless.

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Gotcha! Fair enough. I showed my FIL your comments and I think he may be warming up to the idea of stainless. I found one on ebay for $200 that says it's new but the box has been opened. I figured it was worth the chance since they're usually almost double that. Can't wait to try it out!

Thanks again!

Jason