Had a great weekend, but also have some boat issues...

slow96z

Seaman Apprentice
Joined
Apr 5, 2011
Messages
34
OK, the boat is a 98 Starcraft Aurora with a Mercruiser 250HP and an Alpha outdrive. We were running along fine but heavily loaded with people when the exhaust got loud and steam poured from under the engine cover. I killed the engine and let the steam clear to find that the starboard lower exhaust bellow had ruptured. We got it back to the dock and pulled the bellow, it was completely burned up, looks like it had been for a long time. To get it back to the boat trailer (were at a friends lake house) I replaced the bellow with a 3" plumbing coupler and ran it back to the ramp. The coupler was a couple of inches shorter than the stock piece and did not do a very good job keeping the water in the exhaust, I took on quite a bit in the short trip and the bilge pump failed on me. I know I will have to flush and replace the fluids that were affected by taking on the water (engine oil, trim hydraulic fluid, etc) but I'm not real sure what the process is to find why the bellows burned up in the first place. The temp gauge has shown 200 deg. operating temp since I got the boat, and as a car guy that didn't seem bad, is that too high for a boat?

Here is my current plan of action, please feel free to add steps or make corrections as you see fit!

Inspect and replace impeller
remove, inspect and clean /repair / replace risers and manifolds
inspect t-stat housing, replace t-stat if needed
visually inspect all accessible water passages for debris
replace all 4 upper bellows (assuming damages to all 4, I know both starboard are damaged)

Am I missing anything?
 

MarkSee

Lieutenant Junior Grade
Joined
Sep 10, 2010
Messages
1,172
Re: Had a great weekend, but also have some boat issues...

You also want to verify whether your temp gauge is accurate or not as if it really has been running at 200 degrees, that's way to hot.
I don't know the exact spec for you engine but most current Merc marine t-stat are in the 160-170 range.

Might want to post up the engine s/n to get some more detailed info.

Mark
 

stonyloam

Vice Admiral
Joined
Mar 13, 2009
Messages
5,827
Re: Had a great weekend, but also have some boat issues...

If you burned up the exhaust bellow, it simply means that you were not getting proper water flow to cool the exhaust. Your plan sounds reasonable.
 

haulnazz15

Captain
Joined
Mar 9, 2009
Messages
3,720
Re: Had a great weekend, but also have some boat issues...

If you are closed-cooled, the 160-degree ranges is likely where you should have been running. If open-cooled, then it's probably closer to 140-degrees. Replace the exhaust couplers and the thermostat, and then begin checking the manifolds/risers for blockage that caused the manifold to overheat. It's also likely that your exhaust shutters could be fried, so inspect those at the top of each side of the y-pipe.
 

slow96z

Seaman Apprentice
Joined
Apr 5, 2011
Messages
34
Re: Had a great weekend, but also have some boat issues...

I'm going to get one of those IR Thermometers from HF and see how off the gauge is. I really should replace all of the gauges but that's more than I can swing right now. I'm just hoping it didn't get so hot as to cause damage, but I don't think it did.
 
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