Rev Limiter?

oldsub86

Petty Officer 1st Class
Joined
Sep 9, 2008
Messages
311
I just read the thread with the link to outdrive failure detection and it made me wonder what would happen to the engine if the drive shaft broke. One would exepect the engine to rev up when the load was removed and that there might be damage before the operator was able to back off the throttle. I suspect that the newer units have a form of rev limiter in the electronics but what about older units? Will the points themselves act as rev limiters in the sense that they will normally start to fail to produce accurate timed spark at excessive rpm?

Any ideas on how to avoid a double whammy if something breaks?

Randy
 

Don S

Honorary Moderator Emeritus
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Aug 31, 2004
Messages
62,321
Re: Rev Limiter?

I wouldn't get too worried about it. In 99% of the cases, you get some warning that someing is about to happen.
Worry about a 747 landing on your house, you have about the same odds.
 

oldsub86

Petty Officer 1st Class
Joined
Sep 9, 2008
Messages
311
Re: Rev Limiter?

OK, I'll bite. What would you expect to hear or feel before a drive shaft broke?

I assume this is a relatively rare event but I also expect that when it happens, it is fairly quick and not something that most folks would understand was happening before it was in two pieces.

Randy
 

Jeepster04

Chief Petty Officer
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Jan 5, 2009
Messages
481
Re: Rev Limiter?

What if you have a volvo that decides not to say locked down and you give it too much gas in R. If you cannot hear the engine you have no idea its revving up(big boat). In a panic situation you usually dont keep an eye on the rpms. Well, I do but everyone doesnt.
 

TilliamWe

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Dec 21, 2004
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6,579
Re: Rev Limiter?

OK, I'll bite. What would you expect to hear or feel before a drive shaft broke?

I assume this is a relatively rare event but I also expect that when it happens, it is fairly quick and not something that most folks would understand was happening before it was in two pieces.

Randy

EXTREMELY rare. Outdrive driveshafts don't break every day. And the ones that do break are usually on high performance boats, that guys have modified. So they aren't taken by surprise. If you are running a boat with enough power to break a driveshaft, you'll have your hand on the throttle handle the whole time, anyway. As the motor starts to race away, you'll pull it back.
 

wca_tim

Lieutenant Commander
Joined
May 28, 2007
Messages
1,708
Re: Rev Limiter?

very fast... clunk, clunk, clunk, bang, bang, BANG... and I got out of it apparently just before the center of the ujoint fully cleared the yoke... I've got pisctures of the front of the outdrive and the broken bellhousing somewhere around here, it wasn't pretty...

in the incredibly rare event where you would actually throw the drive shaft... the engine spooling out of control and breaking (although you would be suprised how long a free wheeling small block MIGHT turn before coming unglued) would be a secondary problem. since you would probably be sinking fast enough that it was going to be submerged anyhow...

of course you probably have about the same chance as sinking as a result og being hit by a stray meteor...
 
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