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Old 16-07-2013, 21:55   #1
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Replace homeade? penta md7a exhaust riser/ elbow

Below is a picture of the exhaust elbow I just took off my engine to check for carbon buildup. I was surprised to see that it looks like it was made out of pipes from Home Depot. When I took it off about three pounds of rust can off when I remove the fiber wrap.

1. Is this an acceptable method of make a riser? If so what type of pipe should I use to replace it?

2. Seems that having one fabricated out of stainless steal pipe would be a better option, but I not looking to spend extra money not needed

3. With the water hose disconnected I used the starter to spin the engine to test the water flow. Anyone know how much water should flow? It had very little pressure - almost none. Should I rebuild the water pump while I am at it?

FYI - the engine does not run hot, runs cold if anything. Very little water come out the exhaust normally like spitting. The soot seems to be excessive because it makes my transom within a couple hours.

Thanks for any ideas!

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Old 17-03-2014, 19:55   #2
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Re: Replace homeade? penta md7a exhaust riser/ elbow

I've got the same engine. That riser is funky, but if it works, don't fix it. I think it is so high likely because your engine sits low, below water line. If the riser is below water line, you need that bend. If not...just a 45 bend and 8 inches of pipe with a feed welded on for the water and your done. That is what I did seven years ago and it has been fine. The paint hasn't even burned off.

As for water flow, there should be steady flow, but very low pressure. Remember that is a small fitting it comes out of. You should change your impeller every year or two. If it fails, looses one blade, it can really mess up the engine....I know, it cost me big bucks and two years of overheating grief until I found that little piece of rubber in the engine.

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Old 20-03-2014, 15:39   #3
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Re: Replace homeade? penta md7a exhaust riser/ elbow

I have had two boats with galvanized risers . Take a picture , draw a schematic , its easy to carry the pipe to replace or repair . No doubt stainless is better but it might take several weeks of wages to buy one . Just go to the Home Depot Marina
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Old 20-03-2014, 15:46   #4
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Re: Replace homeade? penta md7a exhaust riser/ elbow

I have the same engine. Low flow is normal for me.

I just made two elbows out of SS. I bought the pipe and some 2 by 3 box section from online metals for about $125. Minimum quantities mean I had enough for two risers, so I made two. Haven't fitted it yet as motor is out of boat. Hardest part was drilling the holes in the 3/16" plate for the flange.
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