Wrong prop? Help please!

[justa150merc]

Hey guys,

I just recently picked up a 1996 Javelin 369FS with a 115 Johnson fast strike (a factory hopped up 60 degree looper). Max RPM for the fast strike is 5000-6000. I want 5800 unloaded and around 52-5400 loaded. The boat is a 17ft fiberglass hull and has a max HP rating of 130 so this isnt an issue of being underpowered.

The prop is a 3 blade stilletto stainless. I noticed that there is no pitch and diameter stamped on the prop itself but pulled some numbers off of the prop hub. #30319 is what numbers I got along with a few others i didnt write down. I did some quick research and the prop seems to be the advantage II which is a 14.25 diameter and 19 pitch that is recommended for V6s 150 HP and above. The previous owner had the local dealer talk him into a prop that had been sitting on clearance for a while and told him it would work well for the boat.

Would this potentially be my issue? Maybe the prop is too aggressive for a 115? I am also wondering if props are interchangeable for the v4 and v6 gearcases on the OMC's? Seems odd to me as I am a mercury man and that is usually not the case with their props.

The #30319 prop is here:


http://boatpropellers.iboats.com/Sti...pellers/30319/


The motor is in good health and runs well from idle up to 5500 RPM roughly with around 550 lbs in the boat, however the prop blows out on anything more than roughly 1/3 trim and if I go into a turn with the trim up even a 1/4 it will also blow out. Also, while running at around 30 and I punch it, it feels strong up to 40 or so, then once I begin to trim up more, it feels like the prop lost all of its bite and its struggling to hit 43-45 mph at 5500 rpm.

I know this boat is good for a solid 50 mph as my neighbor previously owned the boat and with the stock aluminum it hit 49.6. I havent verified with GPS but there is no way I am hitting that speed now.

Also, holeshot is poor to say the least and has terrible bow lift, it seems non existent.. Any incite fellas? Its extremely frustrating having a prop that is constantly blowing out and has a holeshot that is slower than my 12 foot boat with a 9.8 merc on it.

Thanks in advance!

 

[Chris1956]

Well, it sounds like you have a lousy prop with no cupping. However, that Stiletto should run better than that. Is the motor set too high?

 

[justa150merc]

I was thinking that as well. I am 99% sure the motor height was never changed from when the boat was bought new from my neighbor. I am pretty sure it was a straight prop swap. If i were at my cabin I would go take a look and see where the motor sits with the trim down.

From everything I have read regarding these stillettos, they are good runners for the $ and other people with similar setups dont seem to have this problem.

I am used to my previous boat with a 150 merc on it that I could raise and not have any blowout issues with the motor trimmed up very high. On my fathers glastron 17 footer with a merc 150 on it, I can use all of the trim until it hits the tilt position and stops. This is with a 21 pitch enertia prop. Also have no blow out with aggressive trim around turns. The motor seems too low trim wise, but maybe for this hull it isnt.

the picture attached would be a good representation of how high the motor can get before blow out happens.

 

[MikDee]

Pix ain't working, use the little camera icon to upload (and don't write anything on the pic!)

 

[justa150merc]

Better?

Anyways, maybe i shouldn't expect too much, even though it is a strong 115, its still a v4 pushing the boat +600 lbs of people and gear out of the water. Bow lift in my opinion is poor however, at WOT, it is not riding on the back pad of the hull, and seems to be still in the water toward the front of the boat where the driver and passenger seats are.

 

[MikDee]

Sometimes a Merc prop works best. I don't know which one, maybe a spitfire, with straight cut back blade edges.

 

[jestor68]

Have you asked your neighbor (who previously owned it) what prop he was using to go 49.6 mph?

Does that motor have a "V-4" lower unit with 13 splines? I thought only the 25" models used the 15 spline V-6 lower units.

If that's the case, you should be using props with a diameter of about 13.25 or 13.5 designed to fit the intermediate gear case.

 

[dan02gt]

Have you asked your neighbor (who previously owned it) what prop he was using to go 49.6 mph?

Does that motor have a "V-4" lower unit with 13 splines? I thought only the 25" models used the 15 spline V-6 lower units.

If that's the case, you should be using props with a diameter of about 13.25 or 13.5 designed to fit the intermediate gear case.

I agree. My buddy has the Stratos version of that boat (268 I think). With a Evinrude 90 on it. His has the intermediate gear case with a 13 spline prop shaft. He runs a 19P Stilletto Advantage 1 which is 13 spline and 13.25" diameter.