Prop for 1648 w/ Yamaha 40 fourstroke

[12guns]

Anything over 9.9 is new to me, so bear with me. I have a friend that has almost settled on a new Yamaha 40 four stroke. He'll need/want a SS prop. What are some options for pitch? What range does he have to keep the engine running at the right RPM's? Best for holeshot vs. speed? Thanks for any advice!

 

[12guns]

Re: Prop for 1648 w/ Yamaha 40 fourstroke

Anybody deal w/ this prop/boat combo? Thanks!

 

[steelespike]

Re: Prop for 1648 w/ Yamaha 40 fourstroke

Motor rating is 5,000 to 6,000 generally they prop 4 strokes near the top.
The dealer should be able to get him setup.You should setup using a tach and a gps for speed.Dealer should allow prop test for the right pitch.Antivent plate should be visable on plane.Boat will handle better and go faster.
4 strokes are sensitive to poor prop setup.
Although the Yamaha is a fine motor I would be looking at the Evinrude Etec.

 

[RicMic]

Re: Prop for 1648 w/ Yamaha 40 fourstroke

Well, I'm not to far off, I have a 50 two stroke on a lightly loaded 1756. With a 10 3/8" X 14" it turns 5600 rpms and about 34mph. I would guess you would do OK with the same prop in a 12"P.

 

[12guns]

Re: Prop for 1648 w/ Yamaha 40 fourstroke

Ok, my friend bought the 40 Yamaha 4 stroke. He's looking at props. Thought I'd see if there were any other opinions out there. Looks like most guys that we know are running 13 or 15 pitch. My friend wants a good all around prop. He doesn't need excess power, or extreme top end speed, but wants a happy in between. Some guys here are running 12, but looks like mostly with bigger boats that might need the extra power. Any other thoughts??

 

[steelespike]

Re: Prop for 1648 w/ Yamaha 40 fourstroke

A 50 has a higher gear ratio 1.85-1 the 40 is 2.00-1.
Is the 1648 a bare bones with a tiller steer?
I think I would start with a 12.It may be a little light but your better off light
than overpropped. Should give a good hole shot and load carrying.
If it over revs you can just reduce throttle.If it was overpropped you shouldn't use it for an extended period.You should have a tach and a gps.The only way to tell if the setup works.Don't forget the antivent plate should be visable on plane.
imo a ss prop is over kill it might yeild a few mph and some performance.
or asw little as a few tenths compared to a good al prop.
If you boat where hard contacts are probable a ss is expensive to repair.
If soft contacts are likely the ss may hold up better.

 

[12guns]

Re: Prop for 1648 w/ Yamaha 40 fourstroke

Good info, thanks. The boat is mostly bare bones and yes, tiller steer. I talked to him today and he's leaning towards the 13 pitch. Mainly because he knows several people that are running the 13. Only problem is neither he nor I have a tach and will be able to fine tune the prop/motor that well. I was hoping somebody had the same settup that may have suggestions, however I understand there are too many factors for each boat and motor that needs to be propped right. I'll see about the dealer helping him out w/ a tach, thanks again for the great info. I'll pass it on.

 

[steelespike]

Re: Prop for 1648 w/ Yamaha 40 fourstroke

A tinytach is about $47 and easy to install.They have a web site.Be sure to read the details.It is an induction tach and the wire can't be spliced or shortened.
Maybe beg or borrow a gps.

 

[12guns]

Re: Prop for 1648 w/ Yamaha 40 fourstroke

One final question. His dealer told him a 1/2" smaller diameter in the same pitch will allow for a tough more speed? Might make sense as the smaller diameter will spin a tough faster due to less resistance, but I didn't know if that lost resistance would be a good thing or bad. Thoughts?

 

[mommicked]

Re: Prop for 1648 w/ Yamaha 40 fourstroke

Ive recently installed a solas rubex 4 blade alum.on a g3 1860 jon boat w yama F90, went from an alum 3 blade yamaha prop and am very pleased w new performance.it is a world a difference between the two props.cheap too!

 

[12guns]

Re: Prop for 1648 w/ Yamaha 40 fourstroke

My buddy ran the motor over the weekend and is not happy w/ the results. He's picky and expects things to perform better than they should, however I think part of his problem is the prop. His dealer was shipped the wrong brand. It is SS however it looks to be a 1/2" smaller or so diameter with the same pitch? It's also a cheaper brand. Since he had credit and the prop was cheaper, he went ahead and bought it.
Are there much differences between one brand vs. another? How about the diameter? Thanks! Oh, his is 13" pitch. I'm leaning towards telling him 14" if they make it. He may get some top end w/ the slight step up. I'll also try to get him a tach next time. I have a GPS so we'll find out what's best.

 

[steelespike]

Re: Prop for 1648 w/ Yamaha 40 fourstroke

Generally diameter doesn't enter into it except in the extreme like an inch bigger or smaller.Can't we get some details on his performance(I know no tach) but how about a description , hole shot,handling.Any venting problems.Speed?Actual prop size?Is the antivent plate visable on plane?

 

[mommicked]

Re: Prop for 1648 w/ Yamaha 40 fourstroke

What brand of boat is it.my dad has a 1648 Lowe jonboat.its only rated for 35 hp ;weight of the 4 stroke could be a performance issue in the narrow boat.also put some weight in the front of the boat as when he'll be using it. it should handle better in most water conditions w weight forward.

 

[12guns]

Re: Prop for 1648 w/ Yamaha 40 fourstroke

Antivent plate is visible when running. I think the dealership drilled holes and installed, so maybe they knew what they were doing...but I don't know.
He's running a SS 9.5 x 13P. Can't remember what brand, but it's cheaper than the $300 props. Seems like this one was only $175ish? It even looks cheap, high polish vs. brushed SS, no stamp on this outside showing pitch (i'm sure it's on the end or somewhere). He likes to have top end speed, but doesn't want to lack too much with hole shot. I see that alot of people are running 12's, he went w/ 13, and is considering going higher to a 14 or 15. I may just need to get a tach for that.
As mentioned, I'm sure the extra weight does make a difference. I think after a duck season goes by and he sees how smooth and easy on the fuel this motor is, he will like it much better. Plus, w/ the 13 pitch, he can load it down and still run 30-35 mph. I'll keep you posted, thanks for the responses