Should I bother to paint rust on outside of manifolds/riser?

[garycinn]

On my '01 Merc 4.3L TBI with one piece manifolds, there are some spots that are rusted. One such spot is the forward most area of the manifold which is about 3" x 3". It is very rusted. I think it must get hot there because there is a device in front of it that must impede air flow to it so it can stay cool. Another spot is between the manifold and the block -- not as bad, but it is starting.<br /><br />It this outside surface rust just cosmetic or will it eventually affect function/life of the manifolds?<br /><br />In order to get to these spots I would have to take the manifolds off. Is it worth it? How tough of a job? I have the Merc manual, torque wrenches, but I want a realistic picture.<br /><br />I'll need new gaskets -- anything else? I know to get rust off and use a primer. Does Merc's Phantom Blank paint hold up for heat/manifold use?<br /><br />Fresh water boat. 175 hours. Raw water cooled.<br /><br />Thanks!

 

[Don S]

Re: Should I bother to paint rust on outside of manifolds/riser?

It doesn't hurt to paint them, sure makes things look better. The manifolds don't get hot enough to hurt the paint except right where they bolt to the engine and there is no water passages. The rest of it "Shouldn't" get hot enough to hurt the paint. Personally I use Rustolem on the engine. It holds up great.<br />I wouldn't pull the manifolds to paint them, maybe a brush would work in some close areas.

 

[KaGee]

Re: Should I bother to paint rust on outside of manifolds/riser?

I'd paint'em, only cause I don't like the rusty look. It will only get worse too. Not sure about your's, but I can have a manifold off of my engine in about 15 minutes, give or take.<br /><br />You have to use engine paint. I believe TEMPO makes engine paint in the Merc color.<br /><br />Get off as much of the loose stuff as you can, but no matter how much work you put into it, they are gonna rust again anyway. But they'll look cool for a while!

 

[Luna Sea]

Re: Should I bother to paint rust on outside of manifolds/riser?

Touch up paint, get it from the dealer/marine store.<br /><br />I wouldn't pull them though. Way too much work......

 

[Scaaty]

Re: Should I bother to paint rust on outside of manifolds/riser?

The only time I would pull a manlfold would because it failed. Period. If it aint broke, don't fix it. What if you break a bolt off? Those damn things get heat cycled and can be a bear. Seeing as how you're freshwater, wait a few years, save up some daily pennies, and buy a new one.

 

[tommays]

Re: Should I bother to paint rust on outside of manifolds/riser?

gary<br /><br />repaint in place the rust will not really hurt anything but it will spread now that it has a foothold and make it harder to see a problem in the future compared to a cleanly painted surface<br /><br /><br />tommays

 

[Northern Eclipse]

Re: Should I bother to paint rust on outside of manifolds/riser?

Gary If your gonna paint the manifolds consider using Dupli-Color Black hi-gloss ceramic engine paint I used it on my manifolds and it has held up excellent and its only about 6 bucks a can.

 

[garycinn]

Re: Should I bother to paint rust on outside of manifolds/riser?

Thanks for all the recommendations and ideas.

 

[CTD]

Re: Should I bother to paint rust on outside of manifolds/riser?

Paint the rusty areas with rust conversion stuff from Home Depot, then paint. I would just use a brush and do it on the eng. I think it would rust through from the inside long before the outside rust would hurt anything.

 

[DHPMARINE]

Re: Should I bother to paint rust on outside of manifolds/riser?

garycinn,<br />I'd be more concerned about the cause of the rust.<br />Surface rust comes from two sources.Mercruiser is dropping it's watch,or your engine has too much condensation on it.<br /> I think you need to ventilate the engine compartment.<br />DHP

 

[garycinn]

Re: Should I bother to paint rust on outside of manifolds/riser?

Well, I have examined the manifolds some more. The major rust is on the starboard manifold on the vertical surface on the forward most face. There is very little space between this face and the back of the alternator.<br /><br />The port manifold has no rust on this spot. There is nothing in front of this one.<br /><br />The other rusting is much less, but around the inside bend as the one-piece manifold turns into a pipe.<br /><br />I have a few other spots that are pencil diameter or less here and there.<br /><br />I understand that Merc doesn't prime these manifolds. I will do my best to put some paint on these areas to stop the rust.<br /><br />I will be winterizing this weekend and may put up some before and after pictures.<br /><br />Thanks

 

[garycinn]

Re: Should I bother to paint rust on outside of manifolds/riser?

speaking of condensation. I used to have some when I first got my boat last season. I now make sure the bilge is dry (I also routed a locker drain via a thru-hull instead of into the bilge). I also place a fender under my engine hatch so during storage so I don't get a terrarium affect. <br /><br />So, I guess you could say that I had some problems for a half season, but I have corrected them in the past year.