Sea Trial-melted raw water impeller and tube?

WaterKrafter

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Jun 12, 2017
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Yes! The cable was melted somewhat by the overheat...I have been screwing with it all day. Don't know yet weather it is still hung up or not...
 

Rick Stephens

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Aug 13, 2013
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The way to check is have someone shift while you watch the shift interrupt switch while sitting on dry land. If the switch moves at all, then the cable needs replacing. The lower shift cable is a wear item that gets replaced regularly, somewhere around 5 year. They start to wear, get sticky and cause the interrupt to kick in and kill the motor when shifting. There is no downside to getting a Sierra aftermarket cable. They are pretty good, as are the OEM Merc ones.
 

WaterKrafter

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Jun 12, 2017
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So, Commander Rick, if I shift the remote control from neutral to full forward while sitting in cocpit (out of water), and observer the position of switch roller has moved in response to the RC having been put into forward subsequently, such indicates a new cable needs to be outfitted? I am not doubting your experiences here, I just cannot understand not seeing something move upon the RC being moved...in this example into full forward...
 

Bondo

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Apr 17, 2002
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if I shift the remote control from neutral to full forward while sitting in cocpit (out of water), and observer the position of switch roller has moved in response to the RC having been put into forward subsequently, such indicates a new cable needs to be outfitted?

Ayuh,.... If that switch moves, At All when shiftin' the control on the trailer, the lower shift cable is Junk,....

Btw,..... Quit postin' in old threads,....
I deleted yer post in that 6 Year old thread,....
Ya got a thread goin', Right Here,....
Post yer questions in Here,....
 

Rick Stephens

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Aug 13, 2013
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6,118
You might read up here on how the shift interrupt works.

In short: When the boat is in gear, in the water under load from an idling motor, when you pull it out of gear, since the gear teeth are locked in, the cable won't move, instead it pulls the interrupt over momentarily grounding out the coil and killing spark to the motor. As the motor stumbles, the load comes off the gears and they slide out of gear, releasing the pressure on the interrupt allowing the motor to get spark again. Typically this happens so quickly you hardly hear the stumble. But in a properly set up system it happens every time you shift out of gear on the water.

A boat being run on muffs in the driveway, or with the motor not running at all, should have no pressure on the gears when shifting since there is no load on them. If you move the shifter and the interrupt switch moves, you are either far out of adjustment on the linkage or the lower shift cable is worn out and sticking. That cable must be replaced.

The lower shift cable is loaded against the interrupt spring every time you shift out of gear in the water. This makes the cable a wear item, the cable core cuts into the outer sheathing, little by little, making it stickier and sticker. Once it gets where the interrupt is activating without need,, that lower cable then must be replaced. If you overheated the lower cable, it's bad and must be replaced. No purpose in even attempting to 'free it up'. Your lower shift cable is toast. Only reason I say to look at the interrupt while someone shifts in and out of gear is to prove it to you.

Rick
 

thumpar

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Jun 21, 2007
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6,138
Just to add, when checking to see if the interrupt is being engaged you have to have someone watch it while someone works the control. You can't just move the control and go back to see if it moved because you will have missed it happening.
 

achris

More fish than mountain goat
Joined
May 19, 2004
Messages
27,468
.... The lower shift cable is a wear item that gets replaced regularly, somewhere around 5 year. ....

I'm sorry, but I am going to have to dispute this comment.

If nothing has failed that will cause a lower shift cable to have excess load on it or for it to have ingested water, (or it's been burnt by the exhaust due to a 'lack of water' overheat) there is no reason they wouldn't last 20 (or more) years. Mine is 11 years old, my friend's, whom I have maintained since I installed it in 1995, is still original. My previous V6, when the guy I sold it to, sold his boat was also still original and it was 21 years old at that time. I have another friend who has just bought a boat with a 2006 V6 and it also is still on the original cable.

There seems to be a plethora of mis-information regarding replacement times on a lot of Mercruiser items. I have in the past, noted the following...

Bellows. See far too many people saying this is an annual (or bi-annual) replacement item. On a VOLVOs yes, but on a Mercruiser NO. Bellows should easily last 10 years.

Gimbal bearing. Another one that too many people are pulling out a long way before they are due. The old, greaseable types, if greased at service time and the engine kept in alignment, would last many many years. 10 years minimum, 20 years not uncommon. That friend who's engine I installed in '95, still original. Same with my previous V6, and my current 11 year old V6 also, still original. The sealed, non-greaseable, I haven't replaced one yet. The only reason a gimbal bearing would fail is if the bellows leaked and the bearing was flooded, and at that point, I would be replacing the bearing, the unis and the bellows anyway..

Impellers. Here's where is does get tricky. The older MC-1 to Alpha impellers do need to be changed at least on a bi-annual (2 year) basis. If the boat is used less frequently (less than 50 hours a year), the impeller should be changed annually. However, the newer style, Alpha Gen II, are good for a minimum of 3 years/300 hours, as is the Merc High Performance gear oil. I'm not advocating this, but I have seen Gen II impellers that were 7 years old, come out still looking new. And this BS about 'blade set' is just that, BS. The impeller blades will get a 'set' in them about a month after being installed. They all do. And it will stay that way when you pull it out. Blade set is NOT an indicator that the impeller needs to be replaced. If it was, you'd be replacing your impeller every month! Age, burning, blade wear, cracking at the blade root or de-laminating from the hub are the indicators.

I hope this clears up any doubts.

WaterKrafter, Look at my videos for the link to the shift cable adjustment procedure in the 'My Videos' at the bottom of this post's signature..

Chris..........
 

WaterKrafter

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Joined
Jun 12, 2017
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19
SUCCESS! Today she floated, started perfectly, warmed up to temp, idled 700 rpm, all gadges working...AND WENT IN AND OUT OF NEUTRAL AND REVERSE without committing suicide by shift/interrupt switch!

Didn't need to replace either cable after all. Just disassembled shift plate from where it mounts. Took everything apart, lever, cables, bolts, recessed slip barrels (?), and soaked it all in a de-rust anti-corrosive bath overnight and it was a happy day after reassembling and adjusting everything according to the recent reply posts frankly. I have like every Merc service manual and the damn "Sterndrive'

Thanks Rick and Thumper, your guidance has been taken as patient, sincere, and helpful.

Bondo, not sure about yours. Anyway, not meaning to show disrespect, but I have been only involved in this thread since I started it. But it's possible I posted somewhere else for a moment in my fevered despiration...
 

WaterKrafter

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Jun 12, 2017
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Achris, actually I reviewed both the water pump and cable adjust videos while in process of doing both over the life of this thread (last few months)!

Thanks!
 
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