Re: Quicksilver Laser II With Blocked Ventilation Holes?
I had a LaserI years ago and it had a medium sized round hole per blade and no offering of closure. Later came the Laser II with huge square holes (geometry probably has nothing to do with performance one would think) and reading up on them they are deliberately built that way and plastic? plugs are offered to "downsize" the hole to suit the application.
The purpose of the holes is to improve what's called "hole shot". Hole shot basically is getting your boat outta-da-hole and up on top of the water (on "plane). Since horsepower is part rpm's and part torque and other things, if you can get your rpm's up fast, you can develop your HP fast and in doing so, you can spin your prop faster and go faster as a result.
In mastering the hole shot, the holes allow exhaust gas and (cooling water...there, not part of the solution) in the exhaust to flow out the side of the prop barrel and over the next blade coming around. This provides a compressible medium which doesn't offer as much resistance to the engine HP as solid water and as a result the engine doesn't "lug" and rpms get up faster resulting in a quicker hole shot and less bow in your face time and less engine wear.
If the holes are too big for the application, there will be too much uncompressible medium and the prop will cavitate and the boat will have reduced performance. Also, in rough water, holes can allow for cavitation/ventilation and is undesirable.
Sooooo the brilliant engineeers at Merc decided to make a prop for all applications and provided multiple sized plugs (with varying sized holes in them) to plug the prop to suit you.
That is what you have. If yours are plugged completely, one would only assume the previous owner, by trial and error, plugged till he got the results he wanted. Have read on here that high rake props with ports and all are meant for bass boats and may not be what you want in an I/O application. That would support your I/O having solid plugs.....butttt your desires may be different than those of the previous owner.
One thing needs to happen however, you need to have all 3 holes plugged with the same size plug to reduce the opportunity for uneven loading on the blades which could set up vibrations in the power train......phew.
HTH,
Mark
