What is this assembly? (pic) 1996 Mercruiser 5.7 Alpha 1

Goodman98155

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I am new to boat engines and can't identify the function of this actuator-like assmbly on the starbaord exhaust riser. I am beginning to troubleshoot an overheating issue and wonder if this thing has something to do with cooling. Sometimes the plastic actuator shaft is extended and now it is not. Mystery to me!
 

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QBhoy

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That’s the throttle and gear cable linkage, with shift interrupt switch.
If you are having a go at trouble shooting, best have a look at the manual. Good luck. This has nothing to do with it overheating.
 

wrench 3

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It's got nothing to do with your cooling. It's your gear shift linkage. Your's has an easy shift servo.
 

Goodman98155

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Thanks Qbhoy and wrench- makes sense now. I guess I though it was operating a valve of some kind in the riser.
 

achris

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Bolted to the starboard exhaust elbow is the shift plate. You have the remote control gear shift cable (the top one) and the lower shift cable (the lower cable of the two) on there. The plastic 'actuator' is a thing called a 'shift assister'. It's spring-loaded in both directions to assist in getting out of both forward and reverse gear.

Chris....
 
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poconojoe

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The impeller was referenced. It's located in the stern drive.
Go to (Boatinfo.no) to view the manuals for your stern drive and engine.
 

poconojoe

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The impeller is what draws the water into the stern drive, then toward the engine. It's made of rubber and can wear out, depending on usage. The engine also has a water pump that circulates the water throughout the block, just like a car.
If you don't know when the impeller was last changed, then you should change it or get a marine mechanic to do it for you.
 

Goodman98155

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Thanks for the advice. I like the impeller idea and kind of hope it is that out of all of the other myriad possibilities. The boat is in the water but will be out next week for ablative paint. In the meantime I found a service bulletin that describes a way to test the flow from the intake to the engine that I might attempt.
 
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Davidsgara

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Hi all I noticed that the (boatinfo.no) site doesn’t have my information for my 5.0 (2004) model engine no OW012412 ? Could anyone advise where I could get a service manual for this particular model?
 

thumpar

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Hi all I noticed that the (boatinfo.no) site doesn’t have my information for my 5.0 (2004) model engine no OW012412 ? Could anyone advise where I could get a service manual for this particular model?

#31 is for the engine and #14 is for the drive. Both should be there.
 

thumpar

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Like Chris said, #42 is the TKS sup, #41 for MPI sup. Everything else engine wise is in #31.
 

Goodman98155

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The impeller is what draws the water into the stern drive, then toward the engine. It's made of rubber and can wear out, depending on usage. The engine also has a water pump that circulates the water throughout the block, just like a car.
If you don't know when the impeller was last changed, then you should change it or get a marine mechanic to do it for you.

Update: The impeller was totally fried! The boat is still out of the water for other services, but I am confident that the replaced impeller will solve the issue. Thanks all for your advice.
 

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achris

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Well, I can tell you with 100% certainty, that impeller was run dry, and for more than 1 minute.You will also need to replace the housing and cup, and the base as well. That much heat and they are both history.... There's also a very high likelihood the hot exhaust gasses have distorted the water pocket cover in the bottom of the upper housing... Plan on replacing that too. (Or you'll get 'overheats at high speed')

Chris......

EDIT: Just reread the first post... If this engine is a 1996, that makes it a Gen II. That much damage to a GEN II impeller :eek: :eek: I take it back, it wasn't 1 minute. It would need to have been about 5! I had assumed it was a Gen I by the photo! So, no water pocket cover to deal with, and the pump housing is stainless, so it MIGHT be ok. The seal carrier under the pump base will be melted though... Replace that... And pull the exhaust elbows, and replace the shutters (what's left of them!)
 
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Goodman98155

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Well, I can tell you with 100% certainty, that impeller was run dry, and for more than 1 minute.You will also need to replace the housing and cup, and the base as well. That much heat and they are both history.... There's also a very high likelihood the hot exhaust gasses have distorted the water pocket cover in the bottom of the upper housing... Plan on replacing that too. (Or you'll get 'overheats at high speed')

Chris......

EDIT: Just reread the first post... If this engine is a 1996, that makes it a Gen II. That much damage to a GEN II impeller :eek: :eek: I take it back, it wasn't 1 minute. It would need to have been about 5! I had assumed it was a Gen I by the photo! So, no water pocket cover to deal with, and the pump housing is stainless, so it MIGHT be ok. The seal carrier under the pump base will be melted though... Replace that... And pull the exhaust elbows, and replace the shutters (what's left of them!)

You are right- Gen 2. it does look melted, right? I had a professional marine mechanic do the work. He said that the housing was OK. Not sure what he replaced but he is the go-to company for the workyard at my marina so I feel pretty good about it. Not cheap. The previous (and original) owner kept the boat very clean inside and out but was not a mechanical genious. He had attempted to replace the thermostat but didn't use the correct gasket (just a TON of gasket sealant goop) so the temp gauge wasn't working when I bought it. And of course, it had been overheating because of the fried impeller. I have no idea how long it had been like that and how long it had been overheating. That said, the engine runs strong and I am hoping there is no serious permanent damage. It wouldn't suprise me if he ran it dry. Thanks for the analysis, Chris.
 

poconojoe

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As Chris stated...I would check the exhaust shutters. They probably got fried too. And their metal flappers can break loose and fall into some bad places where they can do harm. I found one all the way inside my outdrive when I was doing impeller replacement.

There's also a plastic water tube that joins between the lower and the upper drive. Forgive me, I don't know the proper name for it. Mine was distorted from excessive heat.
Point is...a lot can go wrong when an overheat happens. Always keep an eye on your temperature gauge and make sure water is flowing out of your stern drive.

Be very careful when running it on muffs in your driveway. Make sure your garden hose has enough pressure, your muffs are connected properly and don't run the engine above idle. You can rev it slightly for short low RPM bursts, but don't do it for long.
 
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