Need advice on set up

[spybot]

If this is in the wrong section sorry Mod.

I have a 16ft speedboat very similar to a 16ft Super Sidewinder.
Engine is a Johnson 140 with a 13 3/4 x 21 prop
Boat is 660lbs
Motor is 300lbs
Will have 2 5 gallon plastic tanks.
At present the tanks are in the back either side of the bilge.
Last season ran a Johnson 85. Had cav plate level with bottom of the boat. 3rd hole on the bracket.
Should the 140 be the same ?? or Higher Lower ???
Cheers Andy

 

[Scott Danforth]

the anti-cav plate between the two would be in the same spot.

so where that lands your clamp bracket to your transom may or may not be same location

 

[ahicks]

I would encourage you to be really careful with a boat like that. If you aren't already familiar, look into the potential for "chine walking". The unsuspecting can get a really rude introduction into exactly what that is. If it starts, shut the boat down immediately as once it starts, it ALWAYS gets progressively worse!

 

[spybot]

I would encourage you to be really careful with a boat like that. If you aren't already familiar, look into the potential for "chine walking". The unsuspecting can get a really rude introduction into exactly what that is. If it starts, shut the boat down immediately as once it starts, it ALWAYS gets progressively worse!

Yeah i know the feeling last season once i hit around 40/45 mph she would wobble from side to side a lot. I need to figure out a way to stop this.
I got a set of smart trim tabs added hopefully this will help.

 

[jbcurt00]

Fix chine walk w smart tabs? I doubt it......

perhaps w big oversized fixed tabs or rigid adjustable ones, but not w spring loaded small smart tabs....

function of speed across the water overcoming the hulls capability

biggest reason not to overpower a boat

 

[JASinIL2006]

Actually, Smart Tabs help a great deal with chine walking. Before I installed mine, I would start to chine walk about 48-50 mph. With Smart Tabs, that has been completely eliminated. Fastest I've had it running is almost 60 mph (GPS) and it was rock solid with the tabs. They made a huge difference. You need to make sure they are properly sized and set, though.

 

[spybot]

Actually, Smart Tabs help a great deal with chine walking. Before I installed mine, I would start to chine walk about 48-50 mph. With Smart Tabs, that has been completely eliminated. Fastest I've had it running is almost 60 mph (GPS) and it was rock solid with the tabs. They made a huge difference. You need to make sure they are properly sized and set, though.

I got the ones next size up to what they had recommended for my size boat and engine.
Is it best to have all the weight at the back ?
2 tanks and a battery ? There is a sort of pad built into the hull. From factory not added on.

 

[Faztbullet]

Post a picture of of transom,hull and pad.

 

[ahicks]

I would suspect that the tabs are acting very similar to what just a touch of down trim might do. It would seem to me like either way, you're lowering the nose a hair, which might make quite a difference in your hulls ability to handle speed.

I don't think that's a safe call on all boats though (installing tabs to control chine walk).

The big take away point is, know what chine walk is, and be prepared to shut the power down immediately if you sense anything weird going on - or - be prepared for a lesson you won't soon forget. Hopefully you'll learn that while by yourself.....

 

[JimS123]

Your original question is not answerable on the internet. Motor height is a trial and error thing and needs to be determined empirically. Check all the positions and do a performance curve at each position. When you see cavitation or another anomaly, you are 1 point too high.

For your boat specs, the motor HP is suspect. Does it fall below the max spec given my the boat manufacturer? If not, all bets are off.

Tabs are not appropriate in your situation. Looks like you have a dangerous rig on your hands.

 

[spybot]

I understand the concern about over powering my boat. Hull is rated at 115hp but i have seen 140s on these boats.
Because i have 140 on tap does not mean i will be WOT all day long. This boat is going to be set up for a fast cruiser.
No racing No towing just pottering around and cruising at half throttle. With the occasional blast.

 

[ahicks]

"The occasional blast" is the concern! You know about the danger, and been warned of the potential. Now just use your head. MANY of us have already been there, done that. Everyone I know of has lived to tell about it, and my bet is those with any common sense just had to try it once!

 

[spybot]

"The occasional blast" is the concern! You know about the danger, and been warned of the potential. Now just use your head. MANY of us have already been there, done that. Everyone I know of has lived to tell about it, and my bet is those with any common sense just had to try it once!

I fully understand what your saying. I too have been through it. First month of having her in the water after fixing her up. No one in the boat but me, never even heard of chine walk.
40-45mph she started bouncing from side. No one near me in the middle of Loch Tummel. Yeah i s__t my self probably like everyone else who has been through it. I cut the throttle back to idle then turned round and headed back to shore. It freaked me a bit but then i learned how to drive the boat. Chine walk is something you learn, if you haven't been through well your lucky.

Just to add. On the water i'm mr saftey everyone wears life jackets Not bouncy aids. Lanyard Kill switch attached to me at all times.

 

[JimS123]

I fully understand what your saying. I too have been through it. First month of having her in the water after fixing her up. No one in the boat but me, never even heard of chine walk.
40-45mph she started bouncing from side. No one near me in the middle of Loch Tummel. Yeah i s__t my self probably like everyone else who has been through it. I cut the throttle back to idle then turned round and headed back to shore. It freaked me a bit but then i learned how to drive the boat. Chine walk is something you learn, if you haven't been through well your lucky.

Just to add. On the water i'm mr saftey everyone wears life jackets Not bouncy aids. Lanyard Kill switch attached to me at all times.

Your attitude is why safety on the water has taken a downward trend in recent years. Too many novice boaters have the idea that they can do anything they want and figure that it won't hurt anybody else. Well, it can. The lack of personal responsibility is what makes the Government pass laws that hurt even the responsible citizens.

Some of us take all this very seriously, and if personally harmed we have no problem litigating that will require you sell your firstborn.

 

[spybot]

Your attitude is why safety on the water has taken a downward trend in recent years. Too many novice boaters have the idea that they can do anything they want and figure that it won't hurt anybody else. Well, it can. The lack of personal responsibility is what makes the Government pass laws that hurt even the responsible citizens.

Some of us take all this very seriously, and if personally harmed we have no problem litigating that will require you sell your firstborn.

What my attitude to safety ! Because i try to keep every one safe by wearing Full LIFEJACKETS and i use kill switch lanyard.
You think this is why "safety on the water has taken a downward trend in recent years" ???
How can i improve the safety of me or anyone else in my boat ???? I am asking how to set my boat up. Does that not lead you to think that i am a concerned boater.
You confuse me with some of the idiots i see in your country that buy a boat and go full WOT the very first time and almost KILL themselves or they Kill other people out boating.
I Sir take care on the water.

 

[Chris1956]

Chine walking on a fast boat is a function of trim and speed, along with hull design. Obviously you cannot control hull design, but the other two are under your control.

As was said, hulls can have a speed limit, as a function of their design. i.e.planing hulls with a constant deadrise tend to ride flat in the water and are resistant to trim. Hulls that flatten near the stern trim more and can provide bow lift, leading to more speed.

If you want to drive your boat at high speed, learn what trim and power settings cause chine walk. Learn what happens if you hit a wave at high speed, especially if you hit it at less than a 90* angle.

I have never been successful controlling bad chine walk with just steering. I normally need to cut trim or speed to get it under control. You can compensate for a little chine walk with steering, but only on flat water. Waves will add complexity to the chine walk.

Chine walking can easily lead to capsizing. At high speed that can easily cause injury, especially to head and neck. I would recommend you confine this type of driving to calm water, when you are alone, and when sober. Injuring yourself is a whole lot better than injuring someone else, IMO.

Have fun with it, and check the boat transom for signs of strain, as she is likely overpowered.

My .02

 

[southkogs]

Keep it civil folks. Let's watch the tone and the jibes.

The discussion of safety and overpowering a boat are totally valid. But we've had members who have done so rather safely and are/were pretty good coaches for those who wanted to make a "go-fast" boat.