vacuum advance

[chadjones99]

i just have gotten into jet boats, my question is that my vacuum advance was not hooked up on it, and a friend also bought a jet boat both have the olds 455 .. and his did not even have a vacuum advance on his disturber . so is this a comen thing?
i would think that you would lose hp ? or what?
thanks
chadjones99@netzero.net

[BrendellaJet]

You want a mechanical advance on a jet boat!

[chadjones99]

well any one else have input?
i have heard of vacuum advance and eletric advance(eletronic ignion) but have not seen a mechanical advance....unless you are talking about the vacuum plunger being mechanical. whitch it really is?
is that what you mean?
thanks
chad

[quiet riot]

vacuum advance actually lets the timing advance in a car when it is not under load at cruise rpms and allows it to be slightly more efficient for cruise in a car. With the load applied to a motor to keep a boat at cruise speed you don't want it to be over advanced and you want the better reaction of the mechanical advance. The mechanical advance (centrifugal advance held in place by springs until the ditributor rpm becomes high enough to overcome the spring load keeping it at idle rpm advance) is quicker reacting and generally more precise for more consistant timing.
Engine modifications such as cam, heads, and intake can cause poor or varying vacuum signals which can also lead to issues with vacuum advance in modified engines. Generally high performance sticks to mechanical advance or even locked timing with electronic timing retards for starting, boost or n2o needs.
On a loaded engine (any boat) or high perf (most boats compared to auto types) you want mechanical advance (most electronic ignitions still use mechanical advance.)
jd

[chadjones99]

i see. its been a while sence i have been in a dist.
but i am new to jet boats. so bottom line for this weekend...do i hook up the vacuum advance or leave it un hooked ? i have only ran the boat once before, and it did run good with no advance if i do leave it hooked i would listen out for pinging,
so what do you think ?
thanks
chad

[chadjones99]

well , took the boat out, and cant see any change.
still blow out out when running it hard.