Johnson 115 1995 3 or 4 blade prop

[Josparky]

I bought a 1995 Grumman 19' deck boat it has a 1995 johnson 115 motor on it with a 14x17 aluminum prop. I am pulling me and my kids with it on skis and wakeboard. the hole shot is ok but I think it needs to be better. I was thinking of going to a 4 blade prop but don't know how to determine what size to get. Right now at WOT I am turning 5200 RPM with the 3 blade 14x17 what would I need to go to to keep the RPMs from going above 5500 if I wanted to go to a 4 blade solas. I was thinking the 13x15 but I am just not sure and don't wont to waste the money if it wont work.

Thanks for any help.

 

[dazk14]

Re: Johnson 115 1995 3 or 4 blade prop

Please post the model # of your motor. You are on the cusp of lower unit sizes. Also, what brand/material 14"x17" prop are you currently using.

A 4 blade 15" pitch Solas Amita (no hub kit needed) will work wonders and should put you right on the nickel at 5500.

I'm sure you'll like everything about the switch.

I'm presuming you're running a Large gearcase, so that will have to be verified. Small will work, it just changes the numbers a bit.

 

[Josparky]

Re: Johnson 115 1995 3 or 4 blade prop

Thanks for the reply dazk14. I will get the model off the motor and post it. The brand I do believe it is an OMC Aluminum that is on there now. Thats what it appears to be. Funny the prop you suggested is the exact prop I was looking at before I posted this.

 

[steelespike]

Re: Johnson 115 1995 3 or 4 blade prop

While I realize its only an educated guess wouldn't a 14 X 17 prop indicate a small gear case.
If you look up 17" V6 gear case props none are under 14 1/4 even the 4 blades.

 

[etracer68]

Re: Johnson 115 1995 3 or 4 blade prop

Steel, I think the 115HP is a V4, 13spline.

 

[etracer68]

Re: Johnson 115 1995 3 or 4 blade prop

I looked at the IBoats prop selector, and it shows 115HP a V4 power head, and could be V4(13spline), and V6 lower gear with a 15spline. The OP will have to count the number of splines.

I may have read it wrong, or misunderstood something too. The V6 gear case is 1995 and newer, but also shows 198? and newer, for the V4 gear case.

 

[Josparky]

Re: Johnson 115 1995 3 or 4 blade prop

Thanks guys for any help you can provide. It is a 13 spline I know that much I will get the numbers off the motor and post back.

 

[anzomcik]

Re: Johnson 115 1995 3 or 4 blade prop

I have a similar motor 96 115 Johnson but our hulls are different. My motor also had the 13 spline shaft, which I did have to count because it is listed as either 13 or 15 spline.

I did a prop switch just last week. Originally I had on a 19p 14" 3 blade alum. I was 5050rpm+-

I dropped down to a 13.375 dia 17p SS 3 blade, I now turn 5600rpm lightly loaded and hole shot is very good.

I expected to get only 2-300 rpm gain by droping 2" pitch and going to SS but the change in dia. really did more than I thought it gave me a few hundered more rpm.

Something for you not to over look is 200 rpm for 1/2 of dia change.

 

[Josparky]

Re: Johnson 115 1995 3 or 4 blade prop

Hey anzomcik thanks for the info but I am not sure that staying with the same diameter will work for a 4 blade. I just want to make sure I don't turn more than 5500 rpm with the new prop I was looking at getting the Solas Amita 4 blade 13x15 as they don't have the 15 pitch in a 14" diameter. I just want to make sure it is not going to under prop it so it turns too many rpms.

Thanks again for the info guys anybody else know if this prop will work?

 

[Josparky]

Re: Johnson 115 1995 3 or 4 blade prop

Ok here is the model number for the motor
j115tleor

The prop number that is on it now is.
176214

Thanks Agin maybe someone can tell me if the solas amita will work and not over re the engine.

 

[jestor68]

Re: Johnson 115 1995 3 or 4 blade prop

I believe that you should stay with a 17 pitch with the Solas 4 blade prop, as you are dropping 1-1/4" in diameter ( 12.75 X 17).

Normally, you could expect a 4 blade to run about 100 rpm less than the same pitch 3 blade if the diameters are similar. In this case, the reduction in diameter will cause the 17 pitch 4 blade to actually run up to 200 rpm faster than the 14 X 17 3 blade prop.

Putting the 13 X 15 4 blade on there would be like dropping the equivalent of 3 inches of pitch; which is likely to put you well past your rpm limit of 5500.

 

[Josparky]

Re: Johnson 115 1995 3 or 4 blade prop

Thanks jestor68. Now I have a lot to think about. I was being told by my prop guy around here today that most makers of props had there diameter set to go with the pitch and that the 13x15 4 solas would be ok. Now I am real confused. What you say makes sense but I just don't know that much about going from a 3 blade to a 4 blade I was under the impression that the diameter always went down on a 4 blade to compensate for the other blade and you where suppose to go by the pitch mainly. The prop guy here does not have a 4 blade that he could let me try in his shop but he did try to sell me a michigan 3 blade 13 1/2x15 and said it should put me at 5600 rpms and said that would be ok. But I still would like the 4 blade for pulling I think from what I am seeing on forums. Anybody else have any more thoughts on this. I am getting more confused. I think he just wanted to sell the one he had on the shelf?

Thanks

 

[Josparky]

Re: Johnson 115 1995 3 or 4 blade prop

Hey again WOW thanks for all that effort and info. Just to correct something I posted first. I went out today and ran the boat again. and well it seems I might have been a little off with my first numbers. with boat lightly loaded and me and my 2 boys in there it run around 5000 RPMs WOT at about 3/4 trim and after that started blowing out if I went above 3/4 trim and then would go above 5000 if I trimmed up further than 3/4 trim so I am guessing that I am more around the 5000 no more than 5100 at WOT and 3/4 trim. If I try to trim any more I start getting slippage or cavitation what ever you call it when you start loosing speed and gaining RPMs I call it loosing grip on the prop. If that makes any sense. So I am still guessing with this new info that the 13x15x4 Solas Amita would still be the way to go. Please let me know if you think the same. I can always not run full throttle so it doesn't go over 5500 I hardly ever run WOT any way well really never. I think with the new info and the 4 blade griping better than the 3 blade that I will be right at the 5500 RPM at WOT. Does that sound right? I am only pulling wakeboards and skiers with this boat and cruising around. I have a bass boat for my WOT and fishing fun I bought this one so the wife and kids would have more room when we all go so top end is not an issue.

Thanks again guys for all your help.

 

[dazk14]

Re: Johnson 115 1995 3 or 4 blade prop

It looks like you've answered your question.

The 13x15x4 should be a stump puller. You'll have a junior Ski Nautique with the flexibility to add passengers and still get slalom skiers up before you drown 'em.

The general rule of 1" of diameter equals ~400 rpms works well if comparing apples to apples. That rarely happens, because there are so many other prop variables that are not supplied by manufacturers and the way different rigs respond to those characteristics.

Anzo gave you a good example of diameter changes. Jestor gave you a well thought out conservative option that should give you a bit more hole shot.

For ~$111.99 with free shipping for the Amita4 15pitch, you can't go wrong and you get way more upside potential.

Just an FYI, that motor would run quite reliably a couple hundred rpm above 5500. Later on, for short money, you could always add a little bit more cup to lower rpms a bit if it helps you sleep nights - if it's needed at all.

Order up your Ski Nautique in a box.

 

[Josparky]

Re: Johnson 115 1995 3 or 4 blade prop

Thanks again everyone for your input. I ordered the 13x15 solas aluminum 4 blade. I will post back when I give it a try and let everyone know how it worked out. Hopefully this real world figures can help someone else out. I know there are a lot of calculators out there but from what I was reading on the web those don't always work when going from a 3 blade to a 4 blade so hopefully I made an informed decision here. We will know soon I should have it by Monday hopefully sooner and I will put it on and post back with my findings.

Thanks all.

 

[Josparky]

Re: Johnson 115 1995 3 or 4 blade prop

Well here is my post back like I promised with my findings. Like I said I went with the 13x15x4 solas amita.
Now I turn 5500 RPM at WOT at half trim after that I start loosing little grip it feels like and can turn up to 5800 easy if I keep trimming it up. It really pulls us out of the water now very quick which was what I was after and seemed to be a little better on gas even turning couple hundred more RPM at our pulling speed (weird?).

Now can someone tell me as long as I stay at half trim or below and don't go over the 5500 RPM will it hurt the motor? I am assuming it won't but would like to here from some of you what your thinking is. I sure wish they made a 14x15x4 Amita.

FYI at our pulling speed of around 20 to 25 mph it runs around 4000 RPM and does seem to be better on gas.

Thanks again for your help guys.

 

[etracer68]

Re: Johnson 115 1995 3 or 4 blade prop

Trim gage readings, are pretty much useless, in my opinon. You want to trim, untill you get the best rpm, and speed, before venting the prop. No two boats will read the same on an trim gage. It looks like you got the proformance you wanted. The motor will be more happy at 5500 rpm, going to 5800 for short sprints shoudnt hurt. Good to hear, now go have some fun.

 

[Josparky]

Re: Johnson 115 1995 3 or 4 blade prop

Thanks for the reply etracer68. I have read on a few forums where people say this motor is fine at 5800 RPM but I like staying conservative. It sure is a lot more fun now that I am not drowned before I get up lol. Anybody else know if 5800 hurts this motor?

Thanks

 

[dazk14]

Re: Johnson 115 1995 3 or 4 blade prop

Josparky,

You will not hurt that motor in any way running it at 5800rpm. You'll lose efficiency, but that's a top speed and gas dock item, NOT a rotating mass problem.

In fact, prior to the much improved oils of recent years. By that we mean - it's anti-coking properties -~5800 was the target rpm to minimize carbon build up on the cross flows.

Carbon build up being the enemy of a 2-stroke.

Enjoy your rig.

 

[jestor68]

Re: Johnson 115 1995 3 or 4 blade prop

I'm going to chime in here and recommend that you(and everyone else) adhere to the manufacturer's stated WOT rpm range.

I'm not sure why some folks think that it's OK to tell others that it won't hurt anything to over speed their engines.