A vengeance prop is a no frills stainless prop. It’s little more than a stainless version of the standard mercury 3 blade aluminum prop. It has minimal (if any) rake and cup. It may be stainless, but by no means is it a performance prop. Even mercury says the aluminum version is suitable up to 50mph. Beyond that, you’re not getting much from it.
if you’re running at 52mph @ 4800rpm, you’ve got 12% slip. That’s probably normal for that prop.
As far as wandering goes, that comes with the single I/O territory. It’s from prop torque, and lots of weight on the back.
Dont get too fixated on the diameter as that isn’t something you can’t readily change as the various prop models only come in one diameter for a given pitch.
A large diameter prop will will improve handling response at low speeds for the same reason as a 4 blade. You’ve got more surface area which moves more water per revolution, but the 3 blade large diameter won’t be as noticeable as a 4 blade. The downside is that the wandering may increase.
A small diameter prop will will not yield the same handling response, but it may not wander as much. The downside is the reduced surface area makes it more prone to blow out and the loss of performance from added weight is more pronounced. The only exception here is the mercury enertia. Everyone loves them. It’s a smaller diameter prop that thinks it’s a lot bigger.
For these kinds of boats (18’-22’ runabouts w/4.3-5.7 engines) I consider a small diameter to be anything under 14”, and large is anything over.
For your tach, remove it, turn the selector screw back and forth a few times and put it back in the 8 cylinder position. Sometimes that makes them act better. They’re not the most reliable, but not as bad as they’re made out to be either.
When you say the engine is laboring, can you elaborate? Is it lugging? Or is it screaming along? You also said the acceleration is poor. Does it bog down when you open the throttle and slowly come up? Or does the engine rev up while boat takes off slowly? Have you checked to see if your exhaust shutters are in place? They could cause an exhaust blockage if they break free. It doesn’t sound like it, but it only takes a few minutes to check.
1. First step is to make certain you’re receiving accurate or somewhat accurate info. Deal with the tach.
2. Note your speed at different trim angles and corresponding engine rpm. You don’t need many reference points on this.
3. Check your exhaust shutters because it only takes a few minutes.
is your engine fuel injected or a 4 barrel? There’s a slim chance it could be a 2 barrel which would really throw things off (but this is highly unlikely). Your engine, gearing, and hull length/style means you’ve got a 53-56mph boat.
Rev4/Q4 four blade
mirage plus/thunderbolt large 3 blade
enertia/q3 small 3 blade.
The q3, q4, and thunderbolt are all Quicksilver variants of the corresponding mercury branded props listed above. Finish, features, etc are the same. The only difference is the name on the box and the Quicksilvers tend to save you 20-30% on price.
