View Full Version : Rust on brand new engine.

10-04-2016, 12:36 PM
I bought my 2016 Moomba Mondo literally 6 weeks ago and it has only 16 hours on it. When I was taking everything out for storage I discovered rust on the starboard side of the engine near the bottom. Looking at the pictures below should I be worried about this? I sprayed it with some silicone rust inhibitor oil. Going to the store to get some Fluid Film to spray on it.

There are several smaller rust spots as well.




10-04-2016, 12:56 PM
Your pic looks like it's the exhaust manifolds. I think that is normal because they get quite hot. Mine have a bit of rust on them too.

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10-05-2016, 05:09 PM
I agree, I don't think it is rust. Don't know exactly what it is but I think every engine has some of this to an extent. I don't think I would worry.

10-05-2016, 06:53 PM
It definitely is rust but I'm not going to worry about it. The dealer mechanic came by and said it was normal. I have it documented with them anyway just in case 5 years down the road it turns out to be a really bad thing.

10-05-2016, 10:09 PM
The exhaust manifolds are water cooled therefore the exterior of the manifolds will not get hot enough to damage the paint. This is from poor paint coverage...I would consider poor paint coverage a manufacturing defect. I personally would want it fixed..Not normal..and if the mechanic is calling it normal he approves of this poor quality...

My 04 LSV did not have a speck of rust anywhere on the engine- Not anywhere on the exhaust manifolds. Was just helping my neighbor winterized his 2003 Four Winns 4.3- that engine looked like it was never even run..and it has 340 hours.

10-06-2016, 05:04 AM
I have a hard time telling exactly where the rust is from those pics and especially on the last pic I am unsure if it is all rust or if some of it are reflections from the camera-flash lighting up the rust.

My exhaust risers and manifolds quite quickly gets some spots of rust even on the outside, but I go in salt water and I think at least part of my issue is that it drips water from the under side of the engine hatch on the risers and since they are quite hot, even if it is not enough to ruin the paint, you still get some rust spots. Though my boat is a 2001...
Where the exhaust manifolds connect to the engine, that is where it mounts over the exhaust ports of the engine, the exhaust gasses travel a couple of inches before reaching the actual manifold-body and during those inches gets no cooling. For me that part of the manifold very quickly develops rust as the paint gets damaged. Event the new factory paint on my last manifolds I bought were damaged within hours of usage.
The rest of the manifolds, except maybe for around the bolts and water-connections should however look clean unless they get water on them directly from the outside.
On mine it looks much worse than it is since the bolts mounting the risers to the manifolds rust and it dribbles down over the manifold, though this actually wipes off.

In my case where I run in salt water you would expect to replace the manifolds and risers every 5 to 8 years. And inspect at least every second year. And my engine looks quite rusty here and there on the outside where paint on bolt heads has been nicked or around the spark plugs. So I wouldn't worry about this, but if the engine in fresh waters stays absolutely spotless I wouldn't like it. I would still think the risers will rust out from the inside before the rust on the outside become a real problem.

I would guess that the paint has been damaged by some tool when installing the spark plugs for example, though that is just a guess. Can happen unless you are really careful.

So, on one hand I think this is not really normal and on the other hand I don't think it is anything to worry about except from a cosmetic standpoint.

10-06-2016, 11:19 AM
Every boat I've owned has had a little bit of flakey rust on the risers like that. Also the paint has always been a bit flakey, especially in some of the corners and crevices. It is water cooled but they still get hot enough to be troublesome, I think it's probably also hard for it to survive so many cold-hot temperature cycles and the related thermal expansion. In any case, I think it's fairly normal and I wouldn't be concerned.

10-06-2016, 07:21 PM
I won't worry too much about it. I sprayed the spot with some fluid film so that should stop the rust in it's tracks.

Thanks for the opinions!