[[u]b]Do fat sacks kill boats?[/b][/u]

[wakebum8488]

Do fat sacks ruin your boats engine. ive been trying to talk my dad into buying me some but he loves our boat so much that hes worried that it will kill it. Thankx

[DRAGON88]

depends, if you have a 15 hp outboard than yes it will burn out the motor. we need more spacifics, what kind of boat, what kind of engine, engine HP. You really cant "kill" your boat if you at least follow the weight USCG limit. also how much do you wanna put in it??

[Partyb]

The reason that extra weight, either fat chicks or fat sacs, kill a boat is b/c the engine is overworked. In order to make the engine "work" efficiently you just need to change the gears. That is why a semi truck can only go like 2 mph in first gear, it is a really low gear. Well the gear in your boat is the prop. You will just need to get a smaller/less pitch prop. Otherwise, yes your engine will be affected.

[Mike]

It really depends on the amount of weight, boat size and engine size. They build the new wakeboard boats to handle lots of weight. I'm sure the weight doesnt help, but it doesnt "kill" the boat.

[Nor*Cal]

If you just throw a 500lbs fat sac in the back it's no different than your Dad bringing 2 of his drinking buddies. OR you bringing a couple football linemen.

[OttoNP]

No, It won't really hurt your engine.
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THE APPRENTICE FORUM

[SupremeWake]

"The gear in your boat is the prop" ?? Yes & No. True, a prop pitch change will effect your RPM's, but what about the transmission? Thats where the gears are and in a ski boat the gear ratio is typically 1:1. Thats about as direct as it gets. That is the kind of "truck" gearing that was mentioned. If you have an I/O it's probably not geared with a 1:1 ratio, making your engine work harder.

[OttoNP]

Actually a I/O is geared lower, so your engine works less hard for the same prop torque. A truck is not near 1:1. My truck has these gear ratios:

1st 3.06
2nd 1.62
3rd 1
4th .70
Reverse 2.29

Along with a rear diff ratio of 3.42, so first gear is 10.47:1.

It should be noted that prop pitch and diameter adjustments are used to even out everything. A prop in water is just about ideal for an engine, it provides dampening, much better than a transmission with wheels where everything is more "locked."

You multiply your engine torque by the gear ratio to get your torque at the wheels.

Nick
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MEDICAL MARIJUANA

[SupremeWake]

An I/O typically is not geared lower. They are geared for more speed at the same RPM. This would mean that under stress (towing, weight etc) your I/O or outboard would probably not have the same torque (or even close to it). You can't really be serious in saying that an I/O works less-hard than an inboard under stress.

And I wasn't saying that a truck is geared 1:1. I was stating that was the principle used. They are geared for greatest torque rather than econcomy

[Geoff Standish]

I dunno guys, I once saw a fat sac repeatedly stab a boat. The look in the fat sac's eyes was pure evil. Upon killing the boat it screamed, "I will leave no boat alive!" Then flew off into the night sky....

[Adam Greer]

i better keep an eye on mine

[OttoNP]

This is what I said:

"Actually a I/O is geared lower, so your engine works less hard for the same prop torque. A truck is not near 1:1. My truck has these gear ratios:"

Same prop torque is key,

Alpha One's have been available with the following gear ratios:
1.3
1.47
1.62
1.81
1.94

Mine has a ratio of 1.81. This means that the torque at the prop is 1.81 times the torque at the engine(minus minor losses like bearings). In an inboard with a ratio of 1:1 the torque at the prop is the same as the torque at the engine(minus minor losses like bearings). In that sense by "working harder" I meant more torque at the engine.

Nick

[SupremeWake]

Ok, I see what you were saying. but you do agree that a 1:1 is going to be better for pulling and adding weight than a 1:2 or 1:4 etc...right? That was my point. You are more likely to do damage by adding weight in an I/O than in an inboard.

[OttoNP]

It depends on which way you mean, if by 1:2 you mean 2 prop turns for every 1 turn of the engine then you are right (engine spins slower than prop), but I/O are geared the other way, the prop turns slower than the engine. Most auto/boat report ratios as just a number, like for mine it is 1.81. This is the number of engine turns for every 1 turn of the prop. Any ratio above 1 means engine torque is less than prop torque. Any ratio less than 1 means engine torque is more than prop torque and at one it is equal. In both cases there is some torque loss due to bearings, etc...

Inboard prop's usually have a pitch around 12 and I/O have a prop pitch around 18, so for the same speed an inboard's prop must spin faster. This is why an I/O has the reduction. You can figure out the horsepower your using, it is just the drag force times your speed. If an I/O and an Inboard have the same shape hull and weight then they will have about the same drag and therefore the same horspower requirement. The I/O prop will spin slower with more torque and the inboard's prop will spin faster with less torque, power is torque * rotation speed. Since the I/O is geared the torque at the engine will be less than the torque at the prop and probably about what the inboard's torque is. When they design the drive train they want to use a certain part of an engine's torque curve.

Now, when your talking about something being "hard" on an engine that really depends on how the engine will fail. Most engines fail due to improper maintainance, they overheat or loose lubrication. Next common cause I believe, couldn't find stats, but is probably from wear, as in the piston rings and eventually the cylinder, bearings, valves, etc. This depends more on how many "strokes" the piston takes and therefore a higher RPM would reduce life. Since adding weight requires a higher RPM it would reduce life this way and since inboards run at a higher RPM they would be affected more. But how many people do you know wear out their cylinders?

Time how long it takes your boat to go from 25-20 weighted and unweighted and we can figure out how much more torque/hp is needed because of the weight. Just go 25 and cut the throttle. You could also go over 25 and cut it, start timing at 25 and stop timing at 20.

Nick
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VAPIR NO2 VAPORIZER

[SupremeWake]

... Otto, I understand what the ratio numbers represent and what torque & Hp are and I agree with you. However, I don't think we are talking about the same thing here. Inboard comp-style boats are geared for pulling, which in my opinion makes them more likely to be able to handle more weight. I/O's are typically geared for higher speeds. Do we agree on this? Higher top-end speed is obviously relative to the torque at the prop, however top-end speed has nothing to do with the amount of torque at lower speeds which is where all the work is done for the purpose of our conversation. Right? That is where the 1:1 gearing becomes important for pulling and hauling weight. I hear what you're saying about higher RPM's though.

[OttoNP]

I think we're on the same page, I was just saying that by increasing the gear ratio you make something more suited for towing. Like it you took an inboard with a 1:1 gear ratio and a 12" pitch prop and changed the ratio to 1.81 and left the prop, it would accelerate faster and have a lower top speed. It's top speed is already low which is one reason why this would be bad. Conversly, if you changed the gear ratio on a I/O from 1.81 to 1 and left the 18" pitch prop, it's acceration would decrease further but its top speed would increase providing it had enough power.

Nick
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Babi Mac

[Partyb]

I was trying to oversimplify, plus it is easier to change the prop then the tranny.

[SupremeWake]

Yes, changing the prop would be the thing to do. I was just trying to get at what kind of boat this guy has. I don't think we've heard yet have we?

[wakebum8488]

i have a 1999 sport nautique

[DRAGON88]

you will be fine than, throw mine can pull 2k eaisly!

[SupremeWake]

Your boat will be fine. Just use some common sense. Too much weight makes the wake sloppy anyway. You'll eat up more gas though.

[bcraft]

Wow! I never knew there was so much involved in gear ratio's. . . . Oh wait, that is probably because nobody cares!!!!!. . . simple fact is that after dropping 25-50K on a boat you get a little uptight about what you do to it which is why everyone should buy boats when they are young and don't care. Tell your Dad that boats are meant to go to the lake and have fun on and if he is going to be anal about it he might as well have put the money down on a sailboat so he could float around and never move fast enough to cause any damage. I've got to go back and study the gear ratio's again, I've already forgotten. . . will there be a quiz?

[SupremeWake]

bcraft.... wow, those are some intelligent thoughts. Thanks for your input. Remind me never to consider purchasing a used boat from you. You obviously take good care of your stuff. lol...kidding man.

But seriously, some of us are interested in the actual workings of our boats. That doesn't mean that I am anal about it and don't like to have fun. Maybe I am. Why do you care?

Keep studying those gear ratios craft. There will, in fact, be a quiz... next time, you need to replace your crapped-on transmission. Mines still running good.

[Cyclonecj]

There are quite a few inboards that have a transmission that is not 1to1, mine (toyota direct drive) is 1.23/1, same as direct drive Nautiques. If you pile on the weight, it definitely loads the engine and trans more. Not as much as a car, there's more slippage, so you'll get to a point where you just don't go anywhere. It is an issue, but really only if you buy an underpowered POS. Most boat transmissions are made to handle much larger loads like cruisers, they are not working that hard to move a ski boat, even with extra weight. They usually fail from non-maintenance, not overloading. One or two sacks usually doesn't make that much difference. Four sacks does, but only (really) from a handling standpoint. And gas consumption!

[aussie_stu]

just start worrying when each time you stop water comes over the nose and each time you take off it take 200m to get on the plane