Nissan 9.8 Prop Question

[ScowardNJ]

I have 2003 Nissan 9.8 2 Stroke on a 14' Sea Nymph R all original. A few trips ago i noticed a lack in speed. The motor sounds like it's revving normal. Last night i put a small scratch in the prop hub aligned with the cotter pin in the crown nut. When i hauled the boat i noticed the scratch i made was about 1/4 of a turn off from where it was originally aligned. I'm sorta answering my own question already knowing that the prop is slipping, but is a little slippage normal or should the hub be totally static with zero slippage?

Thanks!

 

[kofkorn]

It should remain static. It's quite possible that the prop is slipping quite badly and by chance only ended up in a location 1/4" away from the original. The easy way to figure it out is to run the motor again. If the mark moves (and odds are it will move significantly), you'll know right away. If it is only moving 1/4", then prop slip isn't your issue. However, normal revving and lack of speed is one of two things: a slipped prop or slipping gears. You would hear the gears. So my money is on the prop.

Good luck!

 

[ScowardNJ]

Thanks for the reply! I just wanted to ask the question before i pick up a new prop. I installed a Hardline Hour/Tachometer also. When i ran the boat last night with me, fishing gear and a cooler. the tach maxed out at 8900 RPM. After reading the instructions again this morning, The tach comes preset at 1 pulse per revolution and I guess the motor revs at 2 pulses per rev. So I guess I'm running WOT at around 4500 RPM's. Should i replace the prop with the same 8" pitch or go up to the 9". There only seems to be 7", 8" & 9" pitch for the Nissan 9.8.

Thanks again!

 

[kofkorn]

Not sure what the recommended RPM is for the Nissan motors. It seems a bit on the low side (I've typically seen 5000-5500). I wouldn't go up in pitch, maybe down to the 7" instead. You'll jump up about 500 rpm, gain a quicker launch and should have similar, if not faster, top speed.

Definitely wouldn't be looking at going up in pitch.

Good luck!

 

[ScowardNJ]

Thanks for the info. The manual says WOT RPM should be between 5000 & 6000. I'm gonna give a 7 pitch a shot.