Replace manifold or just riser?

ajarvis

Cadet
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Dec 18, 2009
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28
I have twin 255's in a 79 Sea Ray 300 Sedan Bridge. I was going to replace the manifolds and risers but reading some posts I had a question. Should I go a head and replace them all or just the risers? I know they can rust through and cause havoc. How often should the riser gaskets be changed as well? I don't know how old they are, it would be good to know I was starting with new, good iron. Any help would be great
 

achris

More fish than mountain goat
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May 19, 2004
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27,468
Re: Replace manifold or just riser?

I have twin 255's ...

255 whats? Mercruiser 255 was 1973/4, and as you said 1979 boat,,,,

Need more input.... :D

Chris........
 

havasuboatman

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Mar 5, 2009
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Re: Replace manifold or just riser?

Why are you replacing them? Don't do so out of hand, take them in and have them checked out.
 

jerryjerry05

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May 7, 2008
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17,924
Re: Replace manifold or just riser?

Iy you are worried then REPLACE!!!! Salt water??? Then definatly replace.
Being as they are possibly 30 years old and you aren't sure of the age then replace.J
 

zbnutcase

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Sep 19, 2009
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2,055
Re: Replace manifold or just riser?

I would replace both riser and manifold,expensive but far cheaper than a new engine. 'nutcase
 

bruceb58

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Mar 5, 2006
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30,454
Re: Replace manifold or just riser?

Risers don't last nearly as long as the manifold. if you think the manifold needs replacing then you definitely want to replace the riser.
 

ajarvis

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Dec 18, 2009
Messages
28
Re: Replace manifold or just riser?

Thanks for the replies.
achris-This is a 1979 Sea Ray 300 SDB, the registration says 79 but the docs fron Sea Ray saythe hull is a 78. It has twin 255 Mercrusier inboards, they were available in thoes years.
Ill pull the manifolds off and have them checked but replace them if there is any question.
Its run in salt water, how often do you guys think the risers should be changed and or the riser gaskets? Thanks again
 

achris

More fish than mountain goat
Joined
May 19, 2004
Messages
27,468
Re: Replace manifold or just riser?

Thanks for the replies.
achris-This is a 1979 Sea Ray 300 SDB, the registration says 79 but the docs fron Sea Ray saythe hull is a 78. It has twin 255 Mercrusier inboards, they were available in thoes years.

Quite right.... I was assuming they were stern drives... My bad...

Ill pull the manifolds off and have them checked but replace them if there is any question.
Its run in salt water, how often do you guys think the risers should be changed and or the riser gaskets? Thanks again

Risers (elbows) should be pulled at 3-4 years, depending on use, then replaced with new gaskets.. Usually they last about 4-5 years, then corrode out. Manifolds usually last 10-12 years, again depending on use.

That's my experience anyway...

Chris.......
 

havasuboatman

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Mar 5, 2009
Messages
904
Re: Replace manifold or just riser?

The reason the hull year is different than the model year is because the last two digits of the HIN are the year the hull was fabricated. Legally, the boat can be sold as a later model, but only by the manufacturer, with a certificate of origin, and it has to be a new boat, of course.
 

ajarvis

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Joined
Dec 18, 2009
Messages
28
Re: Replace manifold or just riser?

Thanks for the info, it's good to get others input. Have a great day and safe boating!!:D
 
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