AQ151C / Weber conversion - revs at WOT?

[Paul McClure]

I've got the boat running and had it out at the weekend. At WOT I'm getting around 4250 max RPM - with the Solex PA1's it would pull way past that. The carb is a 38DGES with the following jetting:

Mains 142
Airs 185
Idle 50's

Since the engine was rebuilt, I'm not sure if the issue is that it needs to loosen up a bit (only 12 hours on the meter) or whether I need to go up a main jet size and get more fuel through..or...???? I suppose at the moment it's good for the running in process, since I've got a built in rev limiter ;-)

 

[Paul McClure]

Should have said - the engine will rev to 5500 RPM when not under load - possibly higher, but I don't want to break the thing again...

 

[el_pescador]

I would check the cable adjustments first.

 

[Paul McClure]

Thanks El..If it revs higher when not under load, would that not suggest that the cable adjustments were OK?

 

[el_pescador]

No. Going over the maximum WOT RPM is possible in virtually every engine with no load. You need to determine the WOT RPM under load. And if no further carb adjustment is possible, then it is time to see if the propeller size is correct.

 

[Paul McClure]

No. Going over the maximum WOT RPM is possible in virtually every engine with no load. You need to determine the WOT RPM under load. And if no further carb adjustment is possible, then it is time to see if the propeller size is correct.

Thanks, I'll check it out. There is scope to go up jet sizes on the mains, just not sure that's the right thing to do. I would have thought that the prop size was OK, since it did achieve higher RPMs with the solexes. Of course the linkage path has changed between then and now, so cables are a possibility.