Exhaust manifold and plastic: WTF?

[jonyb]

What were they thinking?

I've got an 07 Gravity Games boat with the Indmar 340hp motor. I've noticed that there's been a lot of water in the bilge lately so when launching the boat on Saturday, I gave it a little extra trailer time before dropping it in the water. One of the water fittings on the exhaust manifold was leaking. I shut the motor down, loosened the hose clamp and just as soon as I did, the fitting broke. The fittings they use on these motors are plastic. Plastic parts on a cast iron exhaust manifold... What the hell is Indmar thinking? The rest of the part that was left in the hole had gotten so hot that it bonded to it and I had to heat it up and pick it out little bits at a time. No one in town had the right parts to fix it so I had to buy a Mercruiser fitting and a brass reducer to get it all to work. 4 hours later, it's fixed, but the day on the water was lost...

So now, from the water leak, all the bolts on the intake manifold are rusted, all the indentions on it are also rusted, the exhaust manifold was water stains on it...

I suggest everyone replaces the 2 plastic fittings on their exhaust manifolds before you have one break while your out. Had I not noticed this on the boat ramp I would've had a really bad day.

[gmarkham1]

Funny that you bring this up. A few weeks ago I was running across the lake when the engine started cutting out and a strange noise was coming from the engine compartment. The noise was steam rolling out of the manifolds. After the steam cleared, I found those plastic fittings had melted right off on both sides.

Took it into the dealer and they said it had gotten hot(no dah). They said they found weeds in the cooling line. Odd that the alarm never went off and when I checked the engine temp immediately after it was 155.

They also noted that they didnt know much about the ETX Cat since it was the first year it was out!

[wakespeak]

Wow I'll check ours next weekend. Are there metal replacement parts?

[jonyb]

Don't know if they have any or not. I'll probably make some stainless ones this winter.

[lowdrag]

I've never had a problem with those fittings on my last boat or current one. I wonder if the 340 with the cats is generating enough additional heat to cause the problem.

[IndyMatt]

Is this problem specific to the ETX Cats? Post a pic while your digging around so we can see where your working. I think I read a follow up post about these plastic parts being a 'on purpose' fail point to overheating~ like you said should be other warnings~ Good luck!

[IndyMatt]

additional thoughts.... i use a raw water strainer to keep weeds and debris out of the raw water system. Is Indmar still using a 160 degree thermostat on these motors? Maybe dropping to a 120 or 140 will provide some more aggressive cooling. Just some ideas... good luck!!

[jonyb]

Finally got some pics of the part that was broke.

[IndyMatt]

Interesting, Seems like a questionable design, but I wonder if there isnt some design that increases cooling water flow through the manifolds. It looks as if you added some brass spacers, but you should also carefully monitor temps and consider lower temp thermostats or careful moitoring of water pump function. Good luck

[jonyb]

Actually, that's the only thing I could find locally. It was either that or miss out on the last few days of the season. The elbow is for a Mercruiser engine and the adaptor is just a reducer to make it work. A replacement part is on the way and it'll be back to stock before next season.