SX 18 boat balance
 

So far each time I have been out in the boat, I have noticed problems with the balance of the boat.

She seems to need at least one adult in the bow or she sits very low at the back.

Without the weight at the front planing is difficult, and even on the plane she is still low at the back.

In our boat, there are two adults and two small kids.

When we had 4 adults and 2 kids, we needed two adults in the bow, 1 driving and 1 adult on the back seat + 1 child, 1 child in the passenger seat. without the two adults at the fron it sat low at the back

What are other people experiences? Am I doing something wrong?

My original boat instructor reccomeded a heavy sandbag in the front.... even he thought it was odd.

Any help is welcome :confused:

What power package do you have?

Many have extolled the virtues of adding Smart Tabs for better bow lift and lower planing speeds. You may want to look into those.

The power pack is only the 3.0L TKS.

I was aware of people using tabs to help planing... but this usually relates to wanting to water-ski and not wanting to be going too fast but wanting to be on the plane.

I would have thought that adding tabs to a new boat should be unnecessary especially as the boat is lightly loaded?

I am thinking, maybe because I am new to this that I am doing something wrong?

Dave

Dave, you're not doing anything wrong, trust me. Boats just tend to stay unbalanced without equal ballast on each side. I experience it all the time. I ask my passengers to move around once in a while if need be.

I would seriously recommend the smart tabs for you, as they're super easy to use, they do all the work for you. Electric & Hydraulic trim tabs are nice, but require you to constantly be fiddling around with switches trying to get it just right. Smart tabs are spring shock loaded and are about 1/4 the price! If they made them for a boat my size, I'd definitely consider adding them.

Another thing to consider, the addition of weight in the front would be good. Do you have an anchor compartment? Could you possibly put some weight in there (in addition to your anchor?)

Something else to look at is your prop pitch. I would think you have a 19" pitch prop but you may have a 21" on there. If you have a 21" then i would consider dropping it to the 19" or even an 18" which will help you get on plane faster. The Smart Tabs will also help you get on plane faster and hold onto plane longer as they provide some stern lift.

I have exactly the same setup as Bakdraft and I noticed mine came with a 23p 3 blade alu prop; so I will be changing soon to a SST 4 blade 19 or 21p next season. This should also improve my WOT RPM which is now only about 4300rpm.

So I second Mikeyt, this should already improve plane in lower / cruising speeds a lot.

Cheers,

Johan

Hmmm. interesting... I will look into this.. any good websites?

Yep... I meant at least 1 adult on top of the two anchors and chains already present!

The problem is that puting enough weight at the front to be equivalent to a 14 stone adult is a lot of sand!

I am not sure how an SX 18 would perform with a bigger engine at the back that translates up to another 100Kg at the rear. Currently if I do not get the power on hard enough and fast enough I plough so much water the boat feels like it is at 45 degrees and you cannot see anything while driving. This would make water skiing really difficult.

Could you kindly sumarise the benefits / downside of:
Prop pitch
Number of blades
Material

As I am new to this I would value your input....

'k. This isn't an 'exact' science but these are the generalities and there are lots of variables:

Lowering the pitch will increase your rpm's at WOT, lower your top speed but improve your hole shot and mid range punch. A 2" drop in pitch will usually result in a 4-500 increase in rpm. Increasing the pitch has the opposite effects.

3 blade props are standard. They provide the least amount of drag in the water.

A 4 blade prop will give more "bite" allowing you to hold turns at slightly higher speeds as well as improving your hole shot which helps with skiiers and wakeboarders etc. Sometimes, but not always, it comes at the expense of a lower top end.

A 5 blade prop gives maximum bite and are usually seen on higher performance boats and Bravo outdrives as they need to be strong enough to handle the hook-up.

Composite props are okay as spares and are the cheapest on the market. Aluminum is a good compromise and is usually easily repaired if you hit something. Aluminum does flex somewhat but has more give that Stainless
S.S. props are the 'stiffest' and give the best performance but at a much higher cost and they are more expensive to repair.

Mix the above in with the different blade designs (cupped, raked etc) and even mix in slightly different prop diameters (13.75", 14.0", 14.25") and it can become very difficult to make the right choice without getting some professional help. It's not unheard of to have 2 similar or even matching boats with the same prop getting different performance levels.

The idea though is to keep your WOT rpm's within the mfr's recommended range. If your engine range is say... 4400 - 4800, then ideally you want to be running at 4700-4800 rpm at WOT. With your 18', 3.0L i would think that a 19"-20" pitch prop would be best and at outside a 21" prop.

'course, others may have different opinions and experiences!

Thanks for that!

Hmm.. a lot to think about.... I am still interested in the tabs though...