Question regarding Mercruiser 3.0 exhaust

[Glaston175]

My boat is a '93 Glastron with a Mercruiser 3.0 and I've noticed a couple of things recently that is making me wonder if something is wrong with my exhaust.

First is when the boat is running and idling on the lake we get a strong exhaust smell at the rear of the boat that we haven't experienced in the past. I know I know that's where the engine is so duh I'm going to smell exhaust that's normal. This is more so than we've experienced in the past 25 years I've owned it (wow can't believe it's been that long!).

Second is that the boat seems extremely load when cruising. Again, I get it it's a 4 cylinder they aren't known for being quiet. But it's louder than I've ever experienced.

I ran the engine on the trailer and checked for exhaust leaks under the engine cover by running my hand around the rubber connections on the exhaust and all around the head and could feel no leaks.

On the outside I noticed the exhaust coming out from around the transom not the prop. Is this normal? I've added pictures for reference.

Mercruiser 3.0 exhaust
https://imgur.com/gallery/qtil6ZD

 

[AShipShow]

Where you're seeing water come out on muffs is normal.

Do you get any water in the bilge when on the water? Could be a leaking downpipe at the transom plate.
Are all the hose clamps tight on the rubber connectors at the riser?

 

[alldodge]

The water your seeing on muffs is normal

Remove the arrestor and with the motor running look down the carb and see if you see fuel dripping

 

[Glaston175]

The bilge area is dry.

Curious, you both mention where exhaust is exiting on muffs being normal. Is it different when not on muffs?


I will look to see if fuel is dripping in carb while running.

 

[Glaston175]

Ran it with the spark arrestor removed using a flashlight to look down the carb. I did not notice and fuel dripping down carbs.

 

[harringtondav]

...a maybe here: If your exhaust bellows is torn or pulled off from either end more exhaust at idle will bubble up at the transom, and your engine may sound louder, especially when trimmed up. You may not notice a loose bellows with the drive trimmed down on a lift or trailer, but you will see it loose or torn when trimmed up to trailer position.

 

[Glaston175]

harringtondav I will give this a try next.

 

[Glaston175]

BTW here is the spark plugs, cap and rotor. I will replace these today. This will not be the cause of the engine being loud but maybe part of why the exhaust smell is so strong.

Thoughts on condition of plugs? Probably over 5 years old. Engine has 400 hrs on it. They seem wet from gas.

https://imgur.com/gallery/zcdTrxW

 

[alldodge]

Check your boots as harringtondav mentioned for it being loud

Your plugs look to be running a bit rich but not on the major side. Also maybe see a bit of oil burn

 

[harringtondav]

Check your boots as harringtondav mentioned for it being loud

Your plugs look to be running a bit rich but not on the major side. Also maybe see a bit of oil burn

Good observation. '93 is 25 yrs. ago. The stank could just be oil smoke. Glastron 175 Does that 3.0 use oil? If so it's a cheap qt. by qt. fix, as long as the engine isn't getting loose, rattly or knocking. Just keep the level on the dip stick, and continue with annual oil changes. If oil consumption is the problem, four new spark plugs each year is another cheap band aid to keep you on the water for as long as possible.

 

[hoowahfun]

BTW here is the spark plugs, cap and rotor. I will replace these today. This will not be the cause of the engine being loud but maybe part of why the exhaust smell is so strong.

Thoughts on condition of plugs? Probably over 5 years old. Engine has 400 hrs on it. They seem wet from gas.

https://imgur.com/gallery/zcdTrxW

I have just about the exact same symptoms on my '87 3.0. Smelly exhaust, and when I pulled the plugs, they had the exact same look to them in the exact same order (assuming yours were laid out in order). My exhaust bellows is brand new and firmly attached on each end. I have also just replaced the exhaust shutter and the two flexible connections above that on the exhaust. Not sure what to make of it. Thought it could be running rich and is most likely burning a little oil on those two middle cylinders. Not surprising for motors getting on up there in age. I've only had it out a time or two so didn't know if that was normal or not.

Interested to see how this turns out and if you find a fix other than a rebuild

 

[AShipShow]

This could be a stretch, but if I recall correctly, the old design of the exhaust flapper in that era had a metal pin that would break off and rattle around in the downpipe/y pipe for v8 and cause a hole in the exhaust... then again, that would cause a water leak.