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Mercruiser 5.7 Exhaust Riser Spacer Question

shaneknagin01

New member
My 21 foot bayliner trophy sits very low in the stern with the 350 in it. The engine is a 70's model chevy marinized. My question is, when I install the 6" riser spacers, what type of hose do I use to connect from the elbow to the y-pipe? The y-pipe is oval and the elbow is oval. Thanks for the help.
 
Hopefully Chris, Bt Doctur, MakoMark, Bondo, Jeff, obatsea, or one of the more knowledgeable guys will chime in and help you.

Do you have enough clearance above the elbows for 6" spacers/risers?
Are you looking for something like these shown below?

Below are 2 examples ONLY. You will want to verify via your engine serial number.



Mercruiser down elbows for 3 and 6 inch spacers 14801A1
https://nuwavemarine.com/mercruiser...cgA1wx7O40UFiIIiqx71x4yUpWpPwBXhoCG8QQAvD_BwE








Or this style below? But again, you will want to verify via your engine serial number.

https://www.ebay.com/itm/Mercury-87...w-Exhaust-Risers-8M2018452-Pair-/143109014960

s-l500.jpg




.
 
Hopefully Chris, Bt Doctur, MakoMark, Bondo, Jeff, obatsea, or one of the more knowledgeable guys will chime in and help you.

Do you have enough clearance above the elbows for 6" spacers/risers?
Are you looking for something like these shown below?

Below are 2 examples ONLY. You will want to verify via your engine serial number.



Mercruiser down elbows for 3 and 6 inch spacers 14801A1
https://nuwavemarine.com/mercruiser...cgA1wx7O40UFiIIiqx71x4yUpWpPwBXhoCG8QQAvD_BwE








Or this style below? But again, you will want to verify via your engine serial number.

https://www.ebay.com/itm/Mercury-87...w-Exhaust-Risers-8M2018452-Pair-/143109014960

s-l500.jpg




.



WOW YOU GUYS ARE AWESOME! So number 5 in the diagram is what I was wondering about extending, however, I did not realize you could purchase the extended elbows and use the same hose. I really appreciate the help!!
 
Hopefully Chris, Bt Doctur, MakoMark, Bondo, Jeff, obatsea, or one of the more knowledgeable guys will chime in and help you.

Do you have enough clearance above the elbows for 6" spacers/risers?
Are you looking for something like these shown below?

Below are 2 examples ONLY. You will want to verify via your engine serial number.



Mercruiser down elbows for 3 and 6 inch spacers 14801A1
https://nuwavemarine.com/mercruiser...cgA1wx7O40UFiIIiqx71x4yUpWpPwBXhoCG8QQAvD_BwE








Or this style below? But again, you will want to verify via your engine serial number.

https://www.ebay.com/itm/Mercury-87...w-Exhaust-Risers-8M2018452-Pair-/143109014960

s-l500.jpg




.

Be aware, That post is from one the most un-knowledgeable poster on this site. He knows nothing of Mercruiser.

As suggested about verifying.................if the original post had been understood, it would be apparent the serial number may not exist based on a '70 engine block being marinized.....

You still need to define what elbow and manifold design you have.
There are two basic types of manifolds so that is key
 
Last edited:
Be aware, That post is from one the most un-knowledgeable poster on this site. He knows nothing of Mercruiser.

As suggested about verifying.................if the original post had been understood, it would be apparent the serial number may not exist based on a '70 engine block being marinized.....

You still need to define what elbow and manifold design you have.
There are two basic types of manifolds so that is key


Gotcha, I have the wet joint manifolds I'm assuming that's the information your needing? Basically I want to add the 6 inch spacers, so I am looking for the proper way to reach from the elbow to the y pipe. Let me know if I'm on the right track thanks.
 
No,

Do you have center exiting manifolds or long rear exiting manifolds?

Exiting meaning where the riser/elbow will mount. In the center of the manifold or at the rear/aft end?
Wet or dry is of no concern for this topic.
 
WOW YOU GUYS ARE AWESOME! So number 5 in the diagram is what I was wondering about extending, however, I did not realize you could purchase the extended elbows and use the same hose. I really appreciate the help!!

Ayuh,...... A longer piece of standard 4" marine exhaust hose can be put in-place of item #5 to extend the needed 6",.....

The oval is just standard round hose, squeezed into an oval,....

A spraycan of Quick Silver Power Tune makes puutin' tight fitting rubber parts together, fairly easy,......
It makes the rubber slicker than snot, but dissipates pretty quickly, so the tight fittin' parts stay put,.....
 
shaneknagin01, as noted in your first post, I realize that you have a replacement engine that likely no longer has the OEM serial number on it.
Your job will be to find out what engine (serial number) had been OEM in your boat, and do your search via that ID.

Also, Bondo makes what may be a good suggestion.
If extending the length of the exhaust hose allows you to align and join these components, it may work just fine.



.
 
Last edited:
The longer piece of hose is what I was thinking. To answer the manifold question it is center exiting.

Then the most cost effective solution would be using exhaust hose cut to length as required with the intermediate solid tubes.

You could acquire them locally, from a boat type scrap yard from any V8 mercruiser.

Remember, It is better to cut long and have to trim back then trying to get it perfect the first time.

If you do not have the intermediate aluminum exhaust tubes the you can used a single exhaust tubing cut to length on each side.
It may not bend as easy as one thinks so consider the intermediate solid tubes.
 
The first thing you need to find out is your exact water level . Then determine how much higher you need the exaust elbows to go . Then use you dumps with longer hose or use the long dumps with a shorter hose
 
You already have the intermediate "dumps" aluminum tubes. Just longer exhaust tubing on the down side of the tubes would be required from what I see.

Also make sure before adding 6 inch risers your engine hatch will close! If not you may have to use 3 inch
 
Exhaust System Requirements
IMPORTANT: It is the responsibility of the boat manufacturer or installing dealer to properly locate the engine and install the exhaust system. Improper installation may allow water to enter the exhaust manifolds and combustion chambers and severely damage the engine. Damage caused by water in the engine is NOT covered by most Manufacturers Limited Warranty, unless this damage is the result of defective part(s).
Determining If Exhaust Elbow Risers Are Required
To determine if exhaust elbow risers are required, take measurements (a) and (b), with boat at rest in the water and maximum load aboard. Subtract (b) from (a). If (a) minus (b) is less than specified in chart, select appropriate size exhaust elbow riser kit and exhaust extension kit that will correctly position exhaust elbow.
riser-height.jpg

Model
(a) Minus (b) Must Be at Least
All​
13 In. (330 mm)​
 
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