Manifold advice

Will 55

Will 55

New Member
Nov 3, 2018
25
Boat Info
'87 230 Weekender
Engines
5.7 L Alpha 1
quadrajet 4 barrel

Tow with: Toyota Sequoia 5.7L
My boat is freshwater only, relatively low hours for an '87, and the manifold is a bit rusted and has been leaking slightly for a few years. Engine has been well maintained and running great. It seems to be cooling ok, though one side seems a bit hotter than the other. I've been afraid to try and change out the manifolds and risers because the job would be tough due to the tight engine compartment, but mostly due to the fact that more than likely, at least one or more bolts will break since these are the original manifolds on a 1987 Merc. Any advice? 5.7 L merc, alpha 1
 
Change them out before they fail. Way to long imo.
 
Change them - If they fail you are looking at replacing the engine. Consider yourself lucky that these have lasted this long. Manifolds are a maintenance item - in salt water we are replacing them about every five years or so.

-Kevin
 
Do I have to reply to both of these threads?

Change them. You risk ruining your engine if they’re leaking.
 
Change them, and use OEM parts.
You can sometimes get a sale on a complete kit for that motor for about $600.00.
 
I would do them for piece of mind. Just finished replacing them on one of my engines. About to do the second one. It wasn't even that bad of a DIY job. They are just heavy.
 
If your worried about breaking bolts, run the engine up to normal operating temp. The heat will reduce the chance of bolts breaking when loosening them.
 
On the two boats that I had surveyed one needed manifolds and the surverior told me that if I bought this boat I would be living on borrowed time.
 
Original from 1987??? Well, I guess you could bite the bullet and change them out. Easy to do if you warm up engine first.....I had to grind the heads off of my 1988 manifold bolts in 2014 because they were so rusted, but then they spun out by hand.
 
Four bolts on the manifold right? When you grinded the heads off the bolts, did you have to pound off the manifold with a mallet?
 
How about riser gaskets? Restricted or full flow?
 
Will 55 said:
How about riser gaskets? Restricted or full flow?
Click to expand...

When you get a complete kit with new bolts and gaskets they usually come with both.
You’ll see which you have when you take yours apart.
Installion tip:
To help with installing the new manifolds, get two appropriate size threaded rods.
Thread them in to two of the holes in the head.
Slip gasket and manifold over them.
Start two bolts in the other two holes.
Remove threaded rods and replace with bolts.
 
Will 55 said:
Four bolts on the manifold right? When you grinded the heads off the bolts, did you have to pound off the manifold with a mallet?
Click to expand...
Nope, manifold just slipped right off. Grinding the bolt heads off WAS an ordeal, though. My face was 2 inches from grinder, sparks aflyin'! had to cut into manifolds to get bolts off completely.
 
Thanks. Wow, that sounds tough. I'm going to wait til next season, winterized now. I'm going to let the bolts soak in penetrating oil for a week, then warm it up close to running temperature and hope for the best. I'll have a grinder ready in case. I'm wondering if it's necessary to replace anything else while I'm at it ... like the exhaust flappers (they're undoubtedly gone), rubber connectors, or down elbows to the Y pipe? I've heard 5.7L 260 doesn't really need flappers.
 
Well I did it. Piece of cake. Bolts came out easy after a soaking with Deep Creep for 3 days. Since this is a freshwater boat, I was happy to find almost zero internal corrosion on the water jackets. All the corrosion was external. The other side isn't leaking and I doubt I will bother to change it this season after what I saw on the side I replaced.
 
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