fuel consumption

[ColRon]

Winegrapewill,
I have an 89 3867 that also have crusader model 350/454ci engines. I been thinking of installing fuel flow meters. Since you have the same engines I would be very interested in your set-up.

[km1125]

I would check to make sure your mechanical advance is working. Your base timing could be perfect but you really need an additional ~24 degrees of timing as you go up in RPM. I've worked on several distributors where the mechanism was rusty and never obtaining full advance. You can take the cap off and rotate the rotor to see if things are moving, but to really know you have to look at the spark timing at various RPMs.

Having that extra 2 degrees of base timing is probably fine unless you are stuck using 87 octane gas. Most of us are at least at 89 or 90, so that extra 2 degrees takes advantage of that, which would give you a skootch more economy and performance. (probably not noticeable unless you could accurately measure it)

Idle mixture isn't going to effect fuel economy by much at all, even if it was off by quite a bit. IIRC, that circuit is around 2 GPH

Also make sure your choke and secondary air butterflies are fully opening. If either of these butterflies aren't fully open, it will cause an increase in fuel consumption but unless they are closed quite a bit then you might not notice the performance drop. The choke can be an issue as they are (or most are) using a 'divorced choke' where the thermo spring is on the manifold. Sometimes the pivot that should be staked in place starts to move around and will cause the choke to not fully open or fully close. It's an easy fix..you just take it apart and re-stake it, then reinstall and adjust.

[AnamCara]

7-8 knots @ 10 gph
16 knots @ 35 gph
WOT @ 27 knots @ 70 gph
Those readings were on my 88 3607 with 340 hp Merc Bluewaters with Floscan
Run with the tide if you can it makes a difference.