Prop spec 6lp stp 315

[Jkraft]

Hey all, I’m having my injectors replaced and turbo cleaned and serviced. My current 4 blade prop is bent and only turns 3800 wide open. Does anyone know the factory spec for the prop? I want them to tune it and allow me to reach 4000, but my mechanic is concerned that after the injectors and turbo it work, if we tweak the prop, it may turn much higher than 4,000. Anyone know the factory specs?

[Norseman]

Did you own the boat before the prop was bent?
If not, ask previous owner what RPM he got before the damage?
The prop on my 6LP-STE is 19X18, four blade, maxes out at 4050 rpm, a tiny bit under-propped perhaps, would like to see 4000 at WOT, but have a spare prop in the garage tweaked to a slightly lower RPM, not tried it yet however: Bottom paint is good after 2 years and not going to haul for just a prop change.

[Jkraft]

Did you own the boat before the prop was bent?
If not, ask previous owner what RPM he got before the damage?
The prop on my 6LP-STE is 19X18, four blade, maxes out at 4050 rpm, a tiny bit under-propped perhaps, would like to see 4000 at WOT, but have a spare prop in the garage tweaked to a slightly lower RPM, not tried it yet however: Bottom paint is good after 2 years and not going to haul for just a prop change.

No, it was bent when I bought it in the fall and he has no idea what wide open was.... he was a sail boater and did not understand the importance of knowing these things... so I’m starting from scratch.

[Tree]

19x19 with a five cup is where you probably want to start assuming you have the standard hurth gearbox set up.

[Jkraft]

19x19 with a five cup is where you probably want to start assuming you have the standard hurth gearbox set up.

Thank you

[RobS]

IMO where Norseman is at with his 19x18 is pretty darn close to perfect, maybe he could add some cup (cheap and easy) and dial her down right at 4,000. Med to heavy cup is important on the 28TE with the big inefficient non-tapered skeg keel messing up any chance for good clean flow to the prop. I also think starting at 19 square is a tad too much wheel and you'll end up over propped under heavier/dirtier conditions. 19 x 18.5 would likely be better. Don't forget to explore the state of the art stuff like Acme and Veem.

[Jkraft]

IMO where Norseman is at with his 19x18 is pretty darn close to perfect, maybe he could add some cup (cheap and easy) and dial her down right at 4,000. Med to heavy cup is important on the 28TE with the big inefficient non-tapered skeg keel messing up any chance for good clean flow to the prop. I also think starting at 19 square is a tad too much wheel and you'll end up over propped under heavier/dirtier conditions. 19 x 18.5 would likely be better. Don't forget to explore the state of the art stuff like Acme and Veem.

Thanks Rob! Great info.

[Jkraft]

So as it tunes out my current prop is stamped 19x18.5

Not sure if that means it’s a 19x18 with a 5 cup OR a 19x18.5 prop. Either way I think I’ll leave it as is and have it repaired and balanced and put it back on and see where we are after the turbo and injector work.

[RobS]

19" dia prop, 18.5" pitch. Cup, if stamped at all, would be set apart a bit and could be a number from 1 to 7, could have a hashtag in front of the number or sometimes they will stamp the word CUP. And I've even come across some with L, M or H stamped for light, medium or heavy cup. You're setup perfect for starting out. Don't forget that the tachometer MUST be verified with a photo-tach (laser) , especially if it's the Yanmar OEM, they are the worst as to accuracy and are not adjustable.

[Jkraft]

19" dia prop, 18.5" pitch. Cup, if stamped at all, would be set apart a bit and could be a number from 1 to 7, could have a hashtag in front of the number or sometimes they will stamp the word CUP. And I've even come across some with L, M or H stamped for light, medium or heavy cup. You're setup perfect for starting out. Don't forget that the tachometer MUST be verified with a photo-tach (laser) , especially if it's the Yanmar OEM, they are the worst as to accuracy and are not adjustable.

You are right for sure! I’m having a hard time getting a good photo tach reading on it. Could I put the tape on the drive shaft and try to get it there? The engine pulley just does not have the access I need.

[RobS]

You can and then adjust by the gear ratio which is most likely 2:1 for your setup but need to check the tag on the gear to confirm.
But c'mon, if my daughter can do it so can you !

[Jkraft]

You can and then adjust by the gear ratio which is most likely 2:1 for your setup but need to check the tag on the gear to confirm.
But c'mon, if my daughter can do it so can you !

She’s hired! What do I need to pay her? Lol

[RobS]

Are you trying to take the reading(s) when underway? Not safe and no need to do that. Get her out for a good run to get the oil hot (remember you have a seawater cooled oil cooler) and then back in the slip, or somewhere calm and protected, do the photo tach readings in neutral in increments up to something in the neighborhood of 3,500rpm and then extrapolate from there what WOT tach error is.

[Jkraft]

Are you trying to take the reading(s) when underway? Not safe and no need to do that. Get her out for a good run to get the oil hot (remember you have a seawater cooled oil cooler) and then back in the slip, or somewhere calm and protected, do the photo tach readings in neutral in increments up to something in the neighborhood of 3,500rpm and then extrapolate from there what WOT tach error is.

Yes i was attempting under way. This is a good idea

[Wfmdfm]

Question on the photo tech. Can you just use a cheep Harbor Frieght one. I see a big swing in prices on them. I was disappointed when they surveyed my boat that he used the Yanmar dash tech to determin WOT.