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Old 08-22-2013, 08:44 AM
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jafo9 jafo9 is offline
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Anyone told you that an FAE is bad for your motor?

Just curious. I put on my FAE last April right before the season and enjoyed it this summer. About 2/3 through the summer, the motor started having problems and culminated in my local MC dealer putting in a reman motor (Rambo Marine). I got a call yesterday from Rambo and they told me the new motor was in and cranked and ran on the hose. They felt that the FAE may have led to the demise of the original motor. We won't have a definitive cause until Jasper gets the motor back and sends a report but it sounded like a rod had come loose and a bearing was long gone. They found metal pieces in the oil. They felt it revved up normally on the hose without the FAE attached but with the FAE attached they felt it was somewhat restricted and didn't rev up as well. They felt that an increase in back pressure was bad for the motor and may have led to its demise.

My first thought was that their theory may be true while in neutral revving the motor, but that while underway the flow of water over the exhaust tip would help pull the exhaust from the motor and overcome any restriction.

Any thoughts are appreciated. Thanks.
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Old 08-22-2013, 08:49 AM
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Back pressure doesn't make rod bolts come loose or aid in spinning a bearing.

I'll add this:

If the FAE caused enough back pressure to harm the motor it would be very noticeable right when it was first installed. Think about all those early styled catalytic converters. When they got clogged to the point of making back pressure cars would run terrible. It would be to the point they wouldn't get over 40 mph or so.

The FAE had nothing to do with the demise of your motor and I'm kind why anyone at Rambo would suggest that.
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Old 08-22-2013, 09:07 AM
Indyxc Indyxc is offline
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Quote:
Originally Posted by CantRepeat View Post
Back pressure doesn't make rod bolts come loose or aid in spinning a bearing.

I'll add this:

If the FAE caused enough back pressure to harm the motor it would be very noticeable right when it was first installed. Think about all those early styled catalytic converters. When they got clogged to the point of making back pressure cars would run terrible. It would be to the point they wouldn't get over 40 mph or so.

The FAE had nothing to do with the demise of your motor and I'm kind why anyone at Rambo would suggest that.
^^^ Fae would not lead to the demise of a motor. If a motor is exhaust restricted it will run at reduced power levels, not develop mechanical issues.
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Old 08-22-2013, 09:07 AM
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I agree that doesn't make sense that FAE would do that. An extra 3 feet of exhaust destroys an engine? I sure hope they are not that sensitive.

I am not an FAE expert but as far as I understand it will behave very differently at speed in the water compared with running on a hose. The speed of the water over the FAE exit will generate lower pressure. This should reduce the absolute back pressure compared when running on a hose. It is also possible (I am not sure if it is) that the absolute back pressure under speed with FAE is actually lower than without, food for thought.
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Old 08-22-2013, 09:12 AM
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Quote:
Originally Posted by jafo9 View Post
Just curious. I put on my FAE last April right before the season and enjoyed it this summer. About 2/3 through the summer, the motor started having problems and culminated in my local MC dealer putting in a reman motor (Rambo Marine). I got a call yesterday from Rambo and they told me the new motor was in and cranked and ran on the hose. They felt that the FAE may have led to the demise of the original motor. We won't have a definitive cause until Jasper gets the motor back and sends a report but it sounded like a rod had come loose and a bearing was long gone. They found metal pieces in the oil. They felt it revved up normally on the hose without the FAE attached but with the FAE attached they felt it was somewhat restricted and didn't rev up as well. They felt that an increase in back pressure was bad for the motor and may have led to its demise.

My first thought was that their theory may be true while in neutral revving the motor, but that while underway the flow of water over the exhaust tip would help pull the exhaust from the motor and overcome any restriction.

Any thoughts are appreciated. Thanks.
How can the water AND exhaust from two 3"-4" exhaust ports possibly go through what looks like a 2-1/2" single exit point without being restricted? An engine is basically an air pump and the air coming out takes up more space than what goes in.

What was the point of installing this?
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Old 08-22-2013, 09:14 AM
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Quote:
Originally Posted by CantRepeat View Post
Back pressure doesn't make rod bolts come loose or aid in spinning a bearing.

I'll add this:

If the FAE caused enough back pressure to harm the motor it would be very noticeable right when it was first installed. Think about all those early styled catalytic converters. When they got clogged to the point of making back pressure cars would run terrible. It would be to the point they wouldn't get over 40 mph or so.

The FAE had nothing to do with the demise of your motor and I'm kind why anyone at Rambo would suggest that.
Not much water in the exhaust stream of a car, though. Adding water adds a lot more back-pressure than if it was just combustion gases, IMO.
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Old 08-22-2013, 09:34 AM
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Quote:
Originally Posted by JimN View Post
Not much water in the exhaust stream of a car, though. Adding water adds a lot more back-pressure than if it was just combustion gases, IMO.
I'm sure water adds some back pressure but not to the point of killing his engine.
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Old 08-22-2013, 09:53 AM
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Traxx822 Traxx822 is offline
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Correct me if I am wrong but something as simple as running 25mph and pulling the throttle back to idle and just slowing down can add back pressure enough to cause damage.

I just blew out an exhaust gasket that was brand new couple weeks ago. If it wasn't from back pressure I don't know what could have caused it.

Jim is right, 2, 3"-4" exhaust outlets run into a 2 1/2" single outlet is going to be more restirctive.

Maybe enough pressure to blow an exhaust gasket. Probably not a motor.

I have been on one boat with FAE installed. And people always say at idle it would do nothing to get the fumes away from the back of the boat (as they would just bubble up) but I have experienced it, the fumes are better, its quieter, you can hear your music without some strange grumble.

I see many benefits to install this. I even want one.
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Old 08-22-2013, 09:55 AM
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Watch the video on their website. The shape of the exhaust creates a vacuum as water passes by. If the boat is not in motion ie revving engine in neutral them there may be some back pressure then. If you look at their graph on back pressure not until almost wot does the back pressure with an fae exceed one without. Back pressure only gets to around the 2 psi range. Running an engine on a hose will not simulate the vacuum that is created from the water passing by. There is another thread on here that says what this is called. It is something like "the vermillion effect". I know that's not the right word but its something like that.
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Old 08-22-2013, 10:08 AM
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Quote:
Originally Posted by Traxx822 View Post
Correct me if I am wrong but something as simple as running 25mph and pulling the throttle back to idle and just slowing down can add back pressure enough to cause damage.

I just blew out an exhaust gasket that was brand new couple weeks ago. If it wasn't from back pressure I don't know what could have caused it.

Jim is right, 2, 3"-4" exhaust outlets run into a 2 1/2" single outlet is going to be more restirctive.

Maybe enough pressure to blow an exhaust gasket. Probably not a motor.

I have been on one boat with FAE installed. And people always say at idle it would do nothing to get the fumes away from the back of the boat (as they would just bubble up) but I have experienced it, the fumes are better, its quieter, you can hear your music without some strange grumble.

I see many benefits to install this. I even want one.
I would say it was installed incorrectly. Did anyone retorque the bolts after the motor was ran to temp?
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