1995 115 HP Evinrude Prop Help

[Traxion]

I'm currently running a 1995 115 HP Evinrude on a 17.5' Sea Nymph aluminum fishing boat. Current prop is a 13 x 19 pitch Stilletto SS prop. Max RPM that I am getting is 4800 with a speed of about 37.5 MPH. I believe I've read that the motor should be around the 5500 range. Altitude is 1500-3000'.

Performance of the boat is as follows- Holeshot is slow, minimal bow lift. Acceration is OK, you really have to jump on the trim to free the motor up. I can fully trim @ WOT (to the point of blowout) on calm water. But in rougher water, grip is poor and I get a lot of blowout. I have to trim down a bit to prevent blowout on the turns as well.

Would going down to a 17P help me attain desired RPM? Will this help with overall grip of the prop? SS vs. aluminum 17P? Thanks for the help!

 

[Dhadley]

Re: 1995 115 HP Evinrude Prop Help

Walleyehed is a lot more familiar with elevation than I am and I'm sure he'll be along shortly. However, that's over 15% slip, just doesn't sound right. Everything you've said indicates to me that the motor should go up. That should help across the entire rpm band.

I'd only pitch down to gain rpm as an absolute last resort. I'd try raising the motor some to see how it reacts.

It sure seems like you could spin a 19 on that boat.

 

[Traxion]

Re: 1995 115 HP Evinrude Prop Help

I'm not familiar with raising the motor (looked at it and isn't what I remember seeing as far as how you'd raise it). So, I can't really tell you what hole/height it is at right now.

Forgot to add I'm running a SE 300 hydrofoil as well. Came with the boat. Ran it without and all the problems are worse.

More info on the boat. 30 gal. fuel, 9HP kicker motor, 2 batteries, probably 200# of misc gear. I'm usually running at the 3000' elevation.

I've ran the boat at the 1500' level and the prop really carries a load well, but the blowout issues are still there along with the slower holeshot.

 

[Dhadley]

Re: 1995 115 HP Evinrude Prop Help

There should be a series of 4 holes on each side at the top of the stern brackets. If the top bolts are in the top hole, the motor is all the way down and can be raised. The bottom bolts are in slots. We use a hoist to raise the motor after the top bolts are out and the bottom ones loosened. Crank it up, reseal the bolts / holes and tighten everything up. Then test (the fun part).

 

[Traxion]

Re: 1995 115 HP Evinrude Prop Help

I did see the slots on the bottom of the bracket. I believe motors is all the way down. How much adjustment is there, I seem to remember maybe 2"?

 

[Dhadley]

Re: 1995 115 HP Evinrude Prop Help

There are 4 holes and they are about 3/4" center to center if I remember correctly. So about 2 1/4" from all the way down to all the way up.

 

[walleyehed]

Re: 1995 115 HP Evinrude Prop Help

Dhadley, this is almost the identical rig I'm running the 15P turbo Jr at 3100ft and getting just under 5900 when tested at 74 degs. (on the looper)

EDIT: Engine is mounted in third set of holes from top.

 

[Traxion]

Re: 1995 115 HP Evinrude Prop Help

Thanks for the help. It sounds like the 17P would probably be the best for me. I would be afraid of over revving at the lower altitudes with the 15P.

How would a Stiletto 17P work? They seem to be plentiful and reasonable. How about aluminum?

 

[Dhadley]

Re: 1995 115 HP Evinrude Prop Help

There ya have it! I told you he'd be along with all the correct altitude info.

PS - one of these days someone is going to have to explain to me how you can over-rev a 2 stroke. As long as there's a load on it you'll be OK. With stock port timing we've turned a V4 crossflow to 7400. Getting to 6900 was pretty easy. We had to really work for the last 500 though!

 

[Traxion]

Re: 1995 115 HP Evinrude Prop Help

I'd imagine at that RPM range you're not working with bone stock powerheads? I understand what you're saying about over revving. I guess I agree to a certain point. Where does the power curve drop off on these motors? I've ran snowmobiles a lot on yes, you can run them 1000 RPM over there recommended RPM range with a load and not hurt them but we really had trouble with cranks if that happened. Weak design was part of it but stuff just didn't want to hold up. Do you believe you'd see a definite decrease in engine life if continually ran above 6000 RPM? Not doubting, just curious. Interesting!

I just want to get good performance without really pushing the motor. That 5500 range will make it scoot just the same. Thanks for all the help!

 

[Dhadley]

Re: 1995 115 HP Evinrude Prop Help

The rpm range has a lot to do with the hull. Yes, absolutely we were over the hp curve but simply because the hull had so much lift there was very little drag so therefore spinning the prop faster made the boat go faster. With very little drag it took less hp to keep it going fast once you got the hull to pop.

The powerhead was stock, that's the rules. We were allowed Boyesen reeds and we made some intake mods. Dry stacked, open exhaust etc. Basically it will finally reach an rpm where it just can't pump any more air and that's it.

Now, if you try that with no load on it, watch out. That's a different story.

 

[Traxion]

Re: 1995 115 HP Evinrude Prop Help

So I ended up putting a 17P Stiletto on the boat. Holeshot is much much better and I think I even gained in top speed by just a touch. Handles load better too. Overall grip is much better, I think I could trim to the lift and still have grip. Starts porpising when I get too high though. Didn't go with the 15P because I still use the boat at about 1000' alt. and didn't want to be underproped there. The 17P seems like a good compromise.

My question is this- I gained very minimal RPM's with the change. 100-200 according to my tach. By ear the motor seems to be running about the same. Voltage reg. is brand new, so the tach is working properly. Any hints here on what is going on?

 

[Dhadley]

Re: 1995 115 HP Evinrude Prop Help

Had the 19 Stiletto ever been reworked?

 

[Traxion]

Re: 1995 115 HP Evinrude Prop Help

Not that I know of. Bought the boat used but nothing points to the prop being reworked.

Just strange, seat of the pants perspective says the prop is a much better choice on the boat. But, the tach really isn't revealing parallel changes.

 

[Traxion]

Re: 1995 115 HP Evinrude Prop Help

It's been awhile and I am still tinkering with going to a 15p like walleyehed runs. I've ran across an Evinrude Viper 13 7/8" 15p in the correct hub and spline (far as I can tell). Anyone have any ideas how this prop would perform on my rig or compared to the 15p Turbo Jr walleyehed is running? Just looking at the prop the design is much more agressive than the Stilleto I am running.

I'm still low on RPM and still get porpising with a heavy load, thus the reason for trying a 15p as well. Currently get about 52-5300 RPM with about 39 mph top speed. Thanks for the help!

 

[Traxion]

Re: 1995 115 HP Evinrude Prop Help

Had an interesting development today. Over the winter, I replace the transom in my boat. Was badly rotted, much worse than I anticipated. Today was the first day on the water since the transom had been replaced. Running the 17p Stiletto still. Apparently, the rotten transom had enough sag and flex to drastically change my trim angles. With the 170 on the old transom, I could trim the motor full out and not have any blowout and minimal porposing with an average load running the motor at around 5200 RPM w/38 mph speed. Today, with that same load and setup, I could only run about 5000 rpm at 37 mph with way less trim. I can't even get close to full trim like I had been, once I trim up I get blow out and serious porposing. I really never thought there could be that much of a difference with the transom replacement, everything is exactly as it was, motor height, etc.

Anyhow, a 15p looks to be needed. I can't seem to find any Turbo Jr's out there, any other props that would work well. I don't know that the Viper is a good choice, need something built a little more for heavy loads than speed. Any ideas here? Thanks!

 

[Traxion]

Re: 1995 115 HP Evinrude Prop Help

Anyone have any input here? I'm really struggling still, even after talking to several different prop companies.