[ph321]

Hi Steve,

It sounds like a nice boat, I had a 2005 build for a few years. Looks like my props also started out 24×29 and I had them adjusted to 24×27.5 for the following fuel burn:

2200 – 18.5
2300 – 19.4
2400 – 20.6
2500 – 22.5
2600 – 24.3
2680 – 27

From my notes, it looks like these were achieved with relatively full tanks and a fresh anti-foul. I noted cruising speed at about 2300rpm of 22knots. They need to be moving at about this speed for a relatively flat ride.

I owned the boat for about four years and on the whole was really happy with it. The engine bay is fairly tight which makes servicing some items difficult. I think it took me four hours to change the starter motor on the port engine whereas the starboard probably would have taken 15 minutes.

Let me know if you have any other questions on them.

Paul

[ph321]

Hi Eric,

It looks like you’re very over-propped. What HP rating do you have? Tony’s article linked below goes into detail on how to prop the QSM. On the plus side, if you’re happy with the performance at 1800rpm you will just have to prop the boat so that it’s burning about the same at say 2050rpm fully loaded and you should be good to cruise there.

Propping the Cummins Marine QSM 11 to Prevent Exhaust Issues

Paul

1 user thanked author for this post.

Tony Athens

[ph321]

Tony,

Thank you for taking the time to reply.

1. I’m OK with this and had the props repitched last time the boat was out of the water. If both engines were showing the results that the starboard engine is I would be 6L/hr below the Cummins fuel graph at 2300rpm where I cruise. This was admittedly with new anti-foul but otherwise as heavy as it will ever be.

2. Noted. It looks like I’ll take the port prop back and get them to take another 0.5″ off.

3. Noted.

4. There is a vacuum guage on the racors and it’s reading doesn’t change as the revs increase. Should I check after the on-engine filter (also new)? Could I just swap the pressure sensors on the fuel rail to see if that affects any of the readings?

5. It’s true I would probably prefer the boat went faster. Having said that, I am part way through trying to get the props correct.

Thanks again for your help.

Paul

[ph321]

I wasn’t really given a choice by the prop shop to keep the difference. I just asked them to take about an inch of pitch off and they gave them back nearly identical. The fuel burns were pretty close beforehand. Is it common for manufacturers to have to put different props on identical engines? Transmissions are ZF285IV with 1.815 ratio.

Engines have about 800hrs and otherwise seem healthy. I don’t have any great photos unfortunately, it’s pretty tight in there. The exhaust risers are still original and are the “doomed to fail” style, they’re on the list to do soon but no signs that they’ve failed yet. Fuel filters were replaced at the time with no difference in load/fuel burn.  I usually cruise at 2300-2350rpms where both engines are below the Cummins’ fuel curve.

Sounds like I should just get half an inch taken off the port prop next time it’s out. I just didn’t see the point in doing this if it was just hiding other issues. 

Thanks,
Paul

[Author]

Replies