OUTLAW EAGLE MANUFACTURING

Ragged Edge · Joined: 20 Jan 2008 Posts: 30 Location: Vancouver Iland BC

When you modify a pump, impeller, wear ring, etc. Shouldn't the pump be tuned so the engine will run at max rpm? A high skew impeller in a 175 will only pull 5000 rpm. Wouldn't the all around performance be better at 5500rpm?

mountainman · Posted: Tue Sep 09, 2008 3:47 pm Post subject:

When you change impellers you are loading the engine more. The high skew draws more water thus more of a load on the engine which equals lower rpm.

Just my thoughts maybe I'm wrong though Shocked

Ragged Edge · Joined: 20 Jan 2008 Posts: 30 Location: Vancouver Iland BC

So if you had a bigger nozzle it would be able to push the water out faster, thus raising rpm, but would lose pressure. Nothing a speedometer and a few hundred bucks of trial and error wont figure out.

mountainman · Posted: Sat Sep 13, 2008 11:25 am Post subject:

Sounds to be right, money time = results
I'm sure that Mercury has spent a little money engineering the pumps to go with the engines, there maybe some things we can do to improve on performance but there maybe losses in other areas.
If you go with a larger nozzle you may lose your hole shot also.

sharky · Joined: 17 Mar 2010 Posts: 39 Location: Grande Prairie

Has anyone tried to bore out the nozzel on a sportjet to bring the rpm back after installing a hi skew impellor? Did it work? Lose hole shot? Gain top speed?

Stump thumper · Joined: 24 Mar 2010 Posts: 24

My 175 only rev's to 5000 with high skew but I read on another forum about someone with a 175 who dropped his main jets to .072 and put in boysen reeds and says he revs to 5400 rpm with high skew. I may look into these mods, seem good results at minimal cost.

shallowman · Joined: 03 Apr 2006 Posts: 199

I have tried every thing possible to make the 175 and the 200 go faster and yes you need to spin it faster but putting in reed and a smaller jet sizes will not do it , your mid range will be better response with reeds and fuel mileage is better with smaller jets , but you rpm's will stay the same or so very little difference, I have tried to bore out the nozzle and i had awesome bottom end no top end , i tried smaller nozzle went 2 mph faster but had a real hard time taking off , with a light boat also , the best thing i every did was put on a hydl, nozzle and power trim and it had inter changeable inserts and there you will have a good combo, also after putting in my UHMW wear ring bottom end was awesome and top end was better too, so with about 4 years of playing around I ended up with about 5 mph gain , , finally just put in a 383 stoker and now better fuel mileage and lots of speed

sharky · Joined: 17 Mar 2010 Posts: 39 Location: Grande Prairie

Thks. Shallowman...... Sounds like. You saved me a summer of trying out all the things I've contemplated over the winter!!! I think ill play with the jetting and spend the rest of th r and d money on beer! See you on the Wapitti

Ragged Edge · Joined: 20 Jan 2008 Posts: 30 Location: Vancouver Iland BC

I have played with many things myself with varying results. I have currently put it all back to stock with high skew and ss ring. I have heavily ported and polished my stator and have been trimming my impeller. Trim and test until I reach desired rpm, then will tune nozzle to pull 5500 rpm.

sounds logical Laughing