Prop help changing from a 85hp Crossflow johnyrude to 120hp looper Johnson---

[Devonaaron]

I am lookign for a prop to take me fast and maintain a good speed I dont really go on joy rides I always have a destination and might go about 15-32 miles round trip. I have a 120 1990 looper I just picked up the motor has a some kind of stainless prop on it but its so chiped up I mean a big chunk out of one of the blades on the black. Not trying to take that prop at wide open to test the waters. I had a 1977 85hp johnson on it crossflow of coarse. was running a 17 pitch prop at about 34 MPH. Needless to say this motor is way more powerful and that 17 pitch was stainless but very thick I kinda liked it because I had no worrie about breaking it or it wearing down in the sand. I am looking to get a ballistics prop basicly a speed prop very very thin blades and I think I could get away with a pitch up 1 or 2 because they are so thin. I think im going to need something like a 23-24 pitch I always go fast with my boat so am looking to get max pitch so I can conserve gas and get to where I wanna go quicker. My brother has a 19 foot Maxum bowrider with a XR6 merc 150hp and hes got a balistics prop his boat the thing must run 55MPH very very fast so with my new 120 looper im looking to push the limits and get the fastest prop I can for what im going to be doing. I dont want to over pitch it but just want it running at about 5500 at WOT.

 

[steelespike]

Re: Prop help changing from a 85hp Crossflow johnyrude to 120hp looper Johnson---

Best way to select a prop is to try to have the prop repaired then get us the pitch and your rpm and speed.If a prop change is in order you can keep it for a spare.Motor height can sometimes gain some speed. In the extreme 2 to 3 mph.once you have your prop keep raising the motor to a point just before venting(cavitation) becomes a problem.

 

[Devonaaron]

Re: Prop help changing from a 85hp Crossflow johnyrude to 120hp looper Johnson---

I really think I'm going to use that junk prop as it is to just see where I'm at rpm wise. I really don't know what kind of stainless prop I should get tho like a ballistic or stilleto I'm just not sure im really looking for some people who know a good amount power difrence between 85hp Crossflow and 120 Hp looper

 

[Dhadley]

Re: Prop help changing from a 85hp Crossflow johnyrude to 120hp looper Johnson---

There's a world of difference between those two motors. Knowing more about your old set up would help, including what kind of hull. If your old motor would turn only - for instance, 5200 then you may still be looking at a 17 to get to your target of 5800-6000. Without any testing with the looper we have to rely on your old set up numbers. You might be happy with a Ballistic but only if you don't try something else.....

 

[Devonaaron]

Re: Prop help changing from a 85hp Crossflow johnyrude to 120hp looper Johnson---

I have a 16 foot trihull glastron boat is about 1000 pounds that's about it what do people have to say about a ballistics prop on a short shaft my boat likes going fast with tilt Up quite a bit