View Full Version : Blown exhaust gasket - wow those bolts were loose!

08-27-2012, 12:27 PM
Last day of vacation last week I was running Mach II trying to dump one of the kids off a tube when suddenly heard the dreaded "tick tick tick" under the engine compartment.

Shut her down, got everyone in the boat, popped the hood, nothing looked bad so started it up and started looking/listening. Blew an exhaust gasket on the number 2 cylinder and appeared that was all so we limped back to camp and called it a day.

Last night at home I climbed in the rear compartment, wrenches in hand, preparing for a battle with stubborn, potentially rusty exhaust bolts and to my shock they were VERY loose. Which explains blowing the gasket. All 6 of them took minimal one handed effort with the wrench - no fighting at all. I have not checked the other side yet but I damn sure will after seeing how loose these ones were. I don't know what the torque specs should be but it has to be more than that. In fact I'll be putting a wrench on every bolt visible and giving it a turn before I button this thing back up.

Going around tightening bolts on and in the engine compartment is not part of my normal maintenance routine but it will be from now on! Granted my boat is 10+ years old the engine is only about 3-4. Still I wouldn't expect that kind of loosening...

08-27-2012, 12:55 PM

if the other side is as loose, I'd probably invest in a new ex mani gasket as I would bet you have had some blowby that has started to weaken the gasket. jsut my .02...

08-28-2012, 07:24 PM
I found a slow leak of water coming from one side of my exhaust manifold. Found out my gasket was starting to go as well. Per Indmar, they only use the black hi-temp Permatex for the gasket, so if the guy doesn't apply enough, it could leak. I think that's what happened to mine. I replaced with the paper type from Skidim, and it has worked great. Larry from Indmar (Enginer Nut) said either the paper or the gasket type material is just fine - they use the Permatex for convience.

Toruqe spec on the Exhaust manifold bolts is 18 to 24 ft-lbs and the riser bolts is 18 to 22 - though the riser bolts are hell to get to. I check my Exhaust mani bolts several times a year, just to be sure.

08-29-2012, 12:35 AM
Well a whopping $8 and 2 beers later it's all back together and purring like a kitten. I probably took more time cleaning up the mating surfaces and touching up the paint than I did on dis-assembly and reassembly. Starboard side exhaust bolts were a combo of sorta lose and tight. Weird.

When I was a kid with a 69 Chevy lowrider I was tightening the header bolts every other day it seemed. Guess I'll keep an eye on the Moomba more.

08-29-2012, 07:55 AM
I think most bolt rust into place before they can back out. Yours did not. Glad it went well.

08-29-2012, 08:09 PM

Can you post a pic of what bolts you are talking about. I just want to make sure I am thinking of the same ones.

08-30-2012, 10:07 AM
Sure - it is 6 bolts, one on each side of the exhaust ports. You can see on the front one where it was blowing past from the breakage and making quite a mess. I was surprised how much paint was gone from the bottom side of the manifold as well making a lot of rust dust...



08-30-2012, 01:38 PM
Looks like a very good time to change the plugs. Very easy to access.

08-30-2012, 03:14 PM

Mine are pretty easy to get at anyway since my entire compartment wall comes out. Haven't changed them in a few years and probably should have but I'm suffering from a gnarly skateboarding wipeout earlier this week and any more squishing myself into a tight compartment would send me off the deep end with the road rash and bruises getting pushed and pulled more.

08-31-2012, 10:40 AM
Go ahead and change the plugs but be sure to shoot video and post it so we can see your pain.

08-31-2012, 06:44 PM
You know that is what kids are for right? get into the spots you do not fit into anymore to do engine work.

Thanks for the photo's. Now I see what you are talking about.

08-31-2012, 06:53 PM
Absolutely. My son is a chip off the old block so to speak and wants to help more than I feel comfortable actually letting him. Now he's old enough that I'll be recruiting him to do the dirty work for me more and more. Especially when it comes to running wiring through those tiny crevices way back in the compartment where I can't see anything.

Got a few winter projects lining up already so he'll have his work cut out for him!

09-01-2012, 12:00 AM
LOL! My skinny 3rd grader puts her little arm up behind the walls to tighten the upholstery up. She's everything I'm not-- young, skinny, limber, smart, sober. Gotta love that kid!