Nitro 482 top speed issues

[hatcreek]

Right now the situation is pretty much unchanged, even if the new drive sleeve increased the performances by a little margin. still max speed around 39-40mph (with no gear, low fuel and 2 big guys)

I guess I'm at a bit of a loss on your speed issue. One of your first posts stated that you had some prop damage...

...the prop is indeed a little damaged

Is that still the case? Just wondering because you mention some (significant?) vibration issues. You've probably already done the following but, if not:

1) Make sure the prop is within spec.

2) Make absolutely certain (visually, not just the gauge) that your motor is trimming properly during operation.

3) Closely inspect the hull to make sure there are no defects that might be causing drag or allowing water intrusion.

And finally, get that motor back down to where you're not having water pressure or over-rev (alarm) issues... It won't live long if either of those is happening on a regular basis.

[francesco_dibene]

I guess I'm at a bit of a loss on your speed issue. One of your first posts stated that you had some prop damage...



Is that still the case? Just wondering because you mention some (significant?) vibration issues. You've probably already done the following but, if not:

1) Make sure the prop is within spec.

2) Make absolutely certain (visually, not just the gauge) that your motor is trimming properly during operation.

3) Closely inspect the hull to make sure there are no defects that might be causing drag or allowing water intrusion.

And finally, get that motor back down to where you're not having water pressure or over-rev (alarm) issues... It won't live long if either of those is happening on a regular basis.

Yes, the prop have some scars, the mechanic opinion (experienced) is that it can be repaired or replaced but it's not the cause of the loss of 15mph on top speed, that's the reason why I'm still looking to other solutions. The answers:

1) yes, it's a Laser II 21p.
2) The trim seems to work visually. It come up, it makes me plane. It seems to work fine.
3) I don't think there's any water instrusion, never have to use the bilge pump, about the other defect, how it looks like? I mean, what kind of damage do I need to look for?

[hatcreek]

Yes, the prop have some scars, the mechanic opinion (experienced) is that it can be repaired or replaced but it's not the cause of the loss of 15mph on top speed, that's the reason why I'm still looking to other solutions. The answers:

1) yes, it's a Laser II 21p.
2) The trim seems to work visually. It come up, it makes me plane. It seems to work fine.
3) I don't think there's any water instrusion, never have to use the bilge pump, about the other defect, how it looks like? I mean, what kind of damage do I need to look for?

Agreed... a few 'cosmetic' scratches/scars on the prop are probably not responsible for a significant loss in performance. However, if the prop is out of spec due to a bent ear (even slightly) or other structural issue, it very well could be the source of your problems (this would be difficult/impossible to diagnose visually). That's why I was wondering about the vibration you reported.

As for hull defects, it could be something like an area of obvious gelcoat damage...



...or something not-so-obvious like hull blistering.



If the blistering is minor, it wouldn't cause such a speed drop. If it's bad, though, it could result in chunking in the gelcoat. You'll have to raise the boat up off of the trailer slightly to inspect for this, as it occurs where the hull rests on the bunks.

You mentioned that the bilge area never has any standing water. Even so, if there is an area/areas of damage to your hull that's bad enough, it may be waterlogged to some degree and heavier as a result.

Do you have access to a commercial truck scale where you could weigh the rig? It would at least allow you to confirm/eliminate that as a problem.

Again, just trying to throw out a few ideas that you may not have considered.

[driley]

yesterday I had a full afternoon for testing some solutions.

I bought a new drive sleeve because the mechanic though it may be damaged, we mounted it and tried a test run, the result was:
- increased motor vibration at low speed
- a lot faster hole-shot (less than 2 seconds)
- same top speed and same RPM (5500)

Then we tried moving one on the front batteries on the back, the result was:
- same motor vibration at low speed
- same hole-shot as before the drive sleeve change (around 5-6 seconds)
- increased speed by 2mph (same top RPM, 5500)

We then tried to follow the mechanic idea and moved the engine up by 2 holes (now it's on the 4 hole from the top), we then put the boat back on the water and made a test run, the result was:
- lower maneuverability at low speed
- very very stiff steering wheel during the plane making the turns very difficult
- increased the top RPM to 6000+ (the alarm bipped 1 time)
- decreased top speed by 1mph
- decreased leaning of the boat when decreasing speed

The mechanic suggested to lower the engine by 1 hole (put it on the third). I'm still not convinced. What's your idea?

Right now the situation is pretty much unchanged, even if the new drive sleeve increased the performances by a little margin. still max speed around 39-40mph (with no gear, low fuel and 2 big guys)

My Z-6 115HP is mounted in the 2nd hole from the bottom planes great!

[hatcreek]

My Z-6 115HP is mounted in the 2nd hole from the bottom planes great!

d... Your '14 Z-6 is a completely different hull from the 482 it replaced.

[francesco_dibene]

My Z-6 115HP is mounted in the 2nd hole from the bottom planes great!

I don't have hole-shot problems, my problem is the top-speed

I will try to inspect the hull for damages

Thank you!

[Hdspecialty@gmail.com]

I also have a stainless steel prop blazer 21 and at 5500 rpms I get about 44 mph.
Should I change my hub kit?

[Hdspecialty@gmail.com]

What type hub kit do I purchase?
2006 Mercury optimax 115 2 stroke with 21 Lazer stainless steel prop?

[BMCD]

Not sure what a drive sleeve is? your pic makes it seem your not getting lift. This points to a prop issue in my opinion.

what prop are you running now?