DHADLEY could use your help on this one

[keith horne]

I have a question about max rpms. I have a 1986 140hp looper on a 1987 19.8f chaparral sorry but dont know the weight of the boat. But what full throttle rpms should this engine run at i have four props to dail in with one is a 13.75 x 15 omc aluminum prop boat will snap you head back when taking off runs at 6000 rpms other is same as above oem but stainless steel but needs to be reconditioned but should be about the same or a little bit better other is a hustler13.25 x 17 aluminum lost little out of hole turns about 5500 rpms speedo says about 43mph trimmed out wish i had gps maybe down the road but anyway last prop is a cabelo's 12.75 x 19 stainless steel comes out of hole like a dog runs at 5100 rpms all props seem about same speed??? would think there would be a bigger difference also bottom of boat has no paint and like new i also always wax it every spring and at end of season i am a little nuts i know but i take care of what i have work to hard for the little i have. Can anyone tell me what rpms is best and maybe which prop to use and last what maxum speed should i get thanks keith p.s gave all the info i have.

 

[reeldutch]

Re: DHADLEY could use your help on this one

5500 would be your minimum rpms

whatever you do dont run it lower you are lugging the engine that way.

im going to work on a motor like that soon and if i had to run it on my 20'er i would prop it with the 13.75X15. may be the 17pitch.
i always load up my boat with toys and gear and ice and people.
an extra 500 lbs on my boat will be forgiven with a smaller pitch prop.
may be sacrifising top end.
but its a fishing boat.

 

[Dhadley]

Re: DHADLEY could use your help on this one

The small bore loopers can still turn 5800-6000 with no problem. I'd work with a ss prop in at least a 13 1/4" diameter. If you work with the ones you have and raise the motor a bit I think each one will improve some except (maybe) the 15 aluminum. It's doing exactly what we'd expect. Head-snapping holeshot and lots of rpm.

Is the Cabela's prop still a 3 blade?

 

[keith horne]

Re: DHADLEY could use your help on this one

The small bore loopers can still turn 5800-6000 with no problem. I'd work with a ss prop in at least a 13 1/4" diameter. If you work with the ones you have and raise the motor a bit I think each one will improve some except (maybe) the 15 aluminum. It's doing exactly what we'd expect. Head-snapping holeshot and lots of rpm.

Is the Cabela's prop still a 3 blade?

DHADLEY yes its a 3 blade what a shame got it from ebay its like new and the price was right but seems to much for my boat will get my stainless steel omc 13.75x15 done if you think its the best one also engine could be rasied one more hole if that whould help motor is in great shape seems alittle slow top end to me freind lent me his gps and only did 43 mph with the 13.75x15 aluminum omc prop that is in great shape what do you think? p.s. thank you keith

 

[keith horne]

Re: DHADLEY could use your help on this one

mistake

 

[Dhadley]

Re: DHADLEY could use your help on this one

I wouldn't give up on the 19 just yet. I'd really like it to have more diameter but we have to work with what we have. I'd raise the motor a hole or two and see what happens. That should give the 19 some more punch and top rpm's.

 

[keith horne]

Re: DHADLEY could use your help on this one

I wouldn't give up on the 19 just yet. I'd really like it to have more diameter but we have to work with what we have. I'd raise the motor a hole or two and see what happens. That should give the 19 some more punch and top rpm's.

DHADLEY sorry but had wrong info for cabelo's prop its13.25x19 not 12.75x19 maybe thats a good thing also i can rasie motor 1 hole higher thats all thats left.Its getting a little cold nowadays here in south jersey but will rasie motor the hole and try prop and see what rpms it runs what speed do you think this boat should run its just me and a freind cooler and gear i only weigh 150 and freind about 200 thanks again keith

 

[Dhadley]

Re: DHADLEY could use your help on this one

Ok, good. If it's the 13 1/4" diameter I know who makes that prop for them and it's not a bad prop. Lets give that a shot and see where we're at. Take careful notes of the exact rpm change.