Stratos Prop Setup...Results So Far...

Thanks to some help I got on this forum, I have finally got this boat in shape enough to start tuning...

So, from the beginning...I have a 1996 Stratos 278 with an 1994 Evinrude 120 V4. Currently have the engine mounted to a CMC ML-65 jack plate. I have had the luxury of testing two props on this unit so far, but feel that I should be running a little faster and need some help to optimize...

1: OMC 13 7/8 x 19 Viper the boat is running 48 mph (GPS) with driver, passenger and full load of fuel at just over 6200 RPM WOT. Great hole shot (less than a boat length) and acceleration. 14% slip.

2: OMC 13 1/2 x 22 Raker the boat is running 49 mph (GPS) with driver, passenger and full load of fuel at just over 5600 RPM WOT. Hole shot is about 3 boat lengths and acceleration is slower than Viper. 16% slip.

I currently have the prop shaft height at 3" below the bottom of the boat and the AV plate is about 4" above the bottom of the boat. I can trim both props up a little past level before they start to lose their bite with the Raker holding in longer (with one heck of a rooster tail). No problems with ater pressure at current height setting. It holds a strong 6 psi at idle and almost 30 at WOT.

Should this hull and motor combination be running faster or am I about peaked out? I am thinking of trying a 20 Raker or 21 Viper but wanted some input on this setup from you guys beforehand...both of these props seem to have excessive slip compared to what I have read on here...

The boat runs great and it really feels like something nice is about to happen when it gets close to the 50 mark...you can feel it start to lift up that final little bit, but just doesn't make it. There is a little chine walking between 45 and 49 mph. I just think this boat should be running in the mid 50's with this setup, but maybe my looper isn't as strong as it once was...

All input very welcome and I can't wait to hear back from you guys...

Re: Stratos Prop Setup...Results So Far...

I really don't know if you are going to run much faster than that. 49 is pretty darn good for that boat with a 120. I agree you should maybe try a prop in-between the two you have tested though.

My dad had 1995 Ranger Cherokee 17' when they first came out. It was an aluminum boat shaped and laid out just like your Stratos. It had a 1995 Merc 115. We ran about 5 different prop combos on it and the best it ever ran was about 52 GPS. (and I am sure it was lighter than your boat)

-Eli

Re: Stratos Prop Setup...Results So Far...

A 17' boat with a 120, I think that you are real close to what there is available with the load you are carrying. Rooster tail should be about even with the top of your engine cowling so if you are higher than that you might gain that other 1 MPH by trimming down just a tad! I'd like to see what a 19-21 Renegade 4 blade would do for you!

Re: Stratos Prop Setup...Results So Far...

Nice ride, great shots. The Raker should have been able to run higher than the Viper. Did you try the Raker at a higher X dimension?

Man I wish Turbo still had the Lightning Jr's!! Love the gearcase paint!

Re: Stratos Prop Setup...Results So Far...

I think at 1300 lbs your doing pretty good.If you have a front cover you might try it with it on.

Re: Stratos Prop Setup...Results So Far...

Isn't that gearcase something...going to get around to getting it painted at some point...

I've got a new 13 1/4 x 21 Renegade in the shop...bought it off Ebay a few weeks back and after I finally got it here, I spun the hub on the first run so didn't have any results to post for it. Apparently it had sat on the shelf for quite some time and the hub dry rotted. To add insult to injury, my prop shop didn't have the right cone to install the hub and has to have one built in order to install - now looking at 2 weeks before I get it back.

However, I appreciate the comments immensely and apologize if my questions are naive and ambitious...this is my first bass boat and I am just having a ball working on it and I learn something new everyday. This board is great!

Re: Stratos Prop Setup...Results So Far...

Did the Raker run higher than the Viper?

Re: Stratos Prop Setup...Results So Far...

The Raker ran best at the current setting. We tried raising it 1" above it's current setting and lost 3 mph. Water pressure was still good, but dropped it back in the water to where it is at now and got back the 3 mph. Is that typical when you reach the maximum running height?

I have heard you mention in many posts that it depends on whether or not the hull is responsive to small changes in torque when people start talking about making performance enhancements to the engine...where does this Stratos hull rank?

Re: Stratos Prop Setup...Results So Far...

Dhadley said:

Man I wish Turbo still had the Lightning Jr's!!

Click to expand...

What would you recommend...just in case I run across one somewhere?

Re: Stratos Prop Setup...Results So Far...

The Lightning Jr's were an enhanced version of the small Raker. If you came across one probably something in that same 22" range. And yes, it seems you found the sweet spot for the Raker.

You're running at about 15% slip with the both props which I think can get better. Assuming the tach is correct (set on position 6, right?).

How much positive trim do you use to carry the bow? It sounds like it almost steps on the pad and then doesn't.

Re: Stratos Prop Setup...Results So Far...

Nothing of substance to add, except can we make the OP a sticky on how to ask prop questions?

Your first post in this thread is just about perfect. Covered everything I could see in how to ask a prop question.

Re: Stratos Prop Setup...Results So Far...

Dhadley said:

Assuming the tach is correct (set on position 6, right?).

How much positive trim do you use to carry the bow? It sounds like it almost steps on the pad and then doesn't.

Click to expand...

I am so glad you asked that...I just got through putting new gauges in last weekend and I set the new one in the same position as the old one which was just a tad above the 6. I was expecting the indicator to "lock" in either one or the other position, but it just turns. Does it affect the reading if it isn't dead on? I guess the better question is, do I have to measure the RPM another way and then adjust the dial slightly to match?

As for the positive trim, if I set the motor where it runs best and put a level on the AV plate, it is a full bubble off level. I will shoot a photo tonight of where it is trimmed out with a reference to the bottom of the hull...

The slip seemed high to me from what I had read on here with most down in the 8-12% range, but I didn't know what contributes to the high numbers in my case.

Re: Stratos Prop Setup...Results So Far...

Ok, here's something to keep in mind with a pad bottom boat. Once the boat steps up on the pad it will be much higher out of the water. Therefore the motor (prop) will be too. Therefore once it steps up the motor may actually need to be lower. Hydrostreams are like that and so are a lot of other boats. It might be worth a try to let the motor down a tad and test again.

If your tach is an OMC / BRP tach it should click when it's on position 6 or at least have some feel of being "centered" on 6.

Re: Stratos Prop Setup...Results So Far...

I verified the tach setting just to be sure and it is pointed dead on at the 6, but there was no noticable point at which you could tell it centered out.

As for the positive trim...the first photo below is where I was running the Raker and the second photo is where the Viper was running...the Raker would carry the bow very well and it was noticably higher when running at speed. The top of the ruler in the photos is the line to the bottom of the hull.

I haven't got back to the water yet to try dropping it down, but will give it a shot this weekend. I wish that I had a 20 raker or a 21 viper to try on this rig and I haven't made it back to the prop shop to see if maybe he has one of the Turbo's lying around, but if I come across either, I will definitely report back how they ran.

The more and more I think about what was said with respect to it almost getting on pad, that really makes sense with the way it would feel. It felt like it wanted to lift out and take off, but just didn't have enough to do it.

Re: Stratos Prop Setup...Results So Far...

That's the Viper in both shots, right?

Re: Stratos Prop Setup...Results So Far...

Yes. The prop in the previous post pictures are of the Viper. What I did was trim the engine to where the I was running with the Raker (Top Photo) and then trimmed it to where it was running with the Viper (Bottom Photo) during the tests in the first post.

I have made no changes to the height of the engine since the test runs above...

Re: Stratos Prop Setup...Results So Far...

Good info. That confirms that the Raker will run higher than the Viper (Viper vents sooner in trim range) which is what we expected. Sometimes the prop has to be lowered a shade for a little more leverage to pop it up on the pad. I think you're real close.