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All of return water is coming out of the exhaust ports and…

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All of return water is...
All of return water is coming out of the exhaust ports and not the propellar on Mercruiser Alpha One lower unit. How do we make it go through propellar or should it be going through propellar?... Read full answer
All of return water is coming out of the exhaust ports and not the propellar on Mercruiser Alpha One lower unit. How do we make it go through propellar or should it be going through propellar?
Submitted: 7 years ago.Category: Boat
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Answered in 6 minutes by:
6/5/2012
Marine Mechanic: Jason, Marine Mechanic replied 7 years ago
Jason
Jason, Marine Mechanic
Category: Boat
Satisfied Customers: 19,682
Experience: Degree in Marine Technology. Gas and diesel marine mechanic.
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My name is XXXXX XXXXX I will be helping you today. Most questions will involve troubleshooting, and usually take many posts back and forth. Post back with questions as needed.

.

Are you just running it on the trailer and a garden hose?

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Customer reply replied 7 years ago
Yes with muffs. But we have had it in the water and it appears the exhaust is coming out of the two exhaust ports instead the center of the prop. Lots of bubbling under ski deck and sort of a rooster tail type water spray coming out.
Marine Mechanic: Jason, Marine Mechanic replied 7 years ago

Gotcha,

Those 2 ports are called idle relief ports. They are there to make it easier for the engine to idle when in the water. When in the water, there is backpressure from the water itself pushing in on the exhaust outlet, which will make the engine labor to idle. That is the idea behind the idle relief ports. To relieve the backpressure of the lake/sea water.

.

When wether you are on the garden hose. Or in the water. It is normal to get most of your exhaust and water out of those 2 idle relief ports. You probably get close to 90% of your exhaust and water out of those ports at idle and fast idle speeds.

However, when the engine picks up rpms, the flow of water will change from the idle relief ports to the main exhaust port on the drive. (and through the prop). And 90% of the exhaust and water would then come out of the main exhaust. But you still get a little out of the idle relief ports.

.

If you feel you are still getting to much exhaust out of those ports then there are 2 things you need to check.

1. Trim the drive up and look up and underneath of it. Make sure the exhaust bellow between the outer transom plate and the bellhousing is still intact. And that it did not fall off or has holes in it.

2. If that looks good, remove the sterndrive and look into the exhaust cavity and see if it is plugged up at all. If the engine has ever overheated or run hot. What will happen is the exhaust flappers in the exhaust collector (the Y pipe) fall out and can partially plug the main exhaust port.

.

That is what you are looking for.

Feel free to post back with questions

Good luck!

Jason

Jason
Jason, Marine Mechanic
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Satisfied Customers: 19,682
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Customer reply replied 7 years ago

On the overheating issue, we have had the boat in the lake and it didn't exhibit any overheating according the guage. We ran it for at least 30 minutes or more. It seemed that when we accelerated the boat would either spew water up sort of like a rooster tail from under the ski deck or would split it off to each site of the motor. But still very strange pattern. I don't think you could ski behind it.

It appears the exhaust bellow is in tact and in good shape. I just hate to take it to the shop or tear into if there could be something else that we should check.

Do you think it should overheat if the main exhaust port is partially obstructed?

Marine Mechanic: Jason, Marine Mechanic replied 7 years ago

What do you mean by "On the overheating issue"????

.

Scroll up and read your original question. There is no mention of an overheat.

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Customer reply replied 7 years ago

On your response you said, ". If that looks good, remove the sterndrive and look into the exhaust cavity and see if it is plugged up at all. If the engine has ever overheated or run hot. What will happen is the exhaust flappers in the exhaust collector (the Y pipe) fall out and can partially plug the main exhaust port.

I was just wondering if this was the problem would the boat run hot.

Also I was wondering if this is something I need to have taken care of right away. Will it do damage to run it with the exhaust mainly coming out of the relief ports?

Thanks

Marine Mechanic: Jason, Marine Mechanic replied 7 years ago
Start over. You never mentioned that the boat runs hot from the start.
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Customer reply replied 7 years ago

I did not mean to say the boat runs hot. It has not the one time we have had it in the water since we have owned it. I was just referring to you saying that it could have an obstruction in the exhaust that happened if it ever overheated or run hot.

My question was if it does have an obstruction in the exhaust, would it or should it run hot?

It has not overheated since we have had it. However, we have had this exhaust issue since we have had it. I am sorry for the confusion.

Marine Mechanic: Jason, Marine Mechanic replied 7 years ago

An obstruction in the exhaust can cause the engine to run hot. However, at the same time. If the obstruction was big enough, engine performance would also suffer.

.

Post back with questions

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Customer reply replied 7 years ago
OK thanks for your help. I guess our next step will be to remove stern drive and check for blockages.
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