Exhaust leak 1989 Merc 60hp

[Waverider17]

Hi,

I appear to have an exhaust leak coming from the back of my outboard towards the transom bracket. I only found it because I noticed a small splattering of oil in the splash well and then noticed exhaust water dripping down the back of the leg. I've attached a photo of where the leak is coming from and was wondering what the cause of this could be, and if it's safe for light use while I search and wait for parts? The pee stream is normal and no other symptoms, I probably wouldn't have noticed for the rest of the season if I hadn't been cleaning the boat

 

[Chris1956]

Likely a leaky powerhead base gasket. It should be fine to use, provided the exhaust doesn't get under the cowling.

 

[BWR1953]

Hi,

I appear to have an exhaust leak coming from the back of my outboard towards the transom bracket. I only found it because I noticed a small splattering of oil in the splash well and then noticed exhaust water dripping down the back of the leg. I've attached a photo of where the leak is coming from and was wondering what the cause of this could be, and if it's safe for light use while I search and wait for parts? The pee stream is normal and no other symptoms, I probably wouldn't have noticed for the rest of the season if I hadn't been cleaning the boat

I had the exact same problem on my 1985 Merc 50 four cylinder. Only much worse. Big ol' cloud of blue smoke coming out the front. And my engine wouldn't rev up or run normally at all. The exhaust smoke gets sucked into the carbs, which can't "breathe" and get enough fresh air to run the engine.

The "correct" fix is to pull the powerhead and replace the engine mount/bushings and associated parts.




These bushing/mounts are about $90 each and you'll have to replace both of them plus the ancillary stuff as well.



And as usual, once you have the powerhead off, you may find other issues/corrosion and whatnot. I calculated that it would cost me about $300 to replace mine. Plus all the time, aggravation and risk of breakage of old stuff when pulling the powerhead. In my case $300 is a lot of money and it would likely take me 6 months to a year to pull the powerhead and get everything fixed and put back together. It simply wasn't worth it, so I did something else.

My marine mechanic pointed out to me that the reason that my engine wasn't running properly could be due to the exhaust leak.

He told me of a customer who had the same issue and ran his engine without the cowling for 10 years with no adverse effects. He suggested that I try running my engine without the cowling, which I did. And it worked! It was a lot noisier, but ran fine.

So, I came up with a plan to get the cowling back on while having the engine run well.

Here's the video of how that worked for me.

 

[Waverider17]

I had the exact same problem on my 1985 Merc 50 four cylinder. Only much worse. Big ol' cloud of blue smoke coming out the front. And my engine wouldn't rev up or run normally at all. The exhaust smoke gets sucked into the carbs, which can't "breathe" and get enough fresh air to run the engine.

The "correct" fix is to pull the powerhead and replace the engine mount/bushings and associated parts.

View attachment 396467


These bushing/mounts are about $90 each and you'll have to replace both of them plus the ancillary stuff as well.

View attachment 396468

And as usual, once you have the powerhead off, you may find other issues/corrosion and whatnot. I calculated that it would cost me about $300 to replace mine. Plus all the time, aggravation and risk of breakage of old stuff when pulling the powerhead. In my case $300 is a lot of money and it would likely take me 6 months to a year to pull the powerhead and get everything fixed and put back together. It simply wasn't worth it, so I did something else.

My marine mechanic pointed out to me that the reason that my engine wasn't running properly could be due to the exhaust leak.

He told me of a customer who had the same issue and ran his engine without the cowling for 10 years with no adverse effects. He suggested that I try running my engine without the cowling, which I did. And it worked! It was a lot noisier, but ran fine.

So, I came up with a plan to get the cowling back on while having the engine run well.

Here's the video of how that worked for me.

Thanks for taking the time to answer and to look at alternative solutions. I need to pull the power head at the end of this season anyway so I'm assuming that there's no chance of damaging anything if left to run like this for the next 6 months?

 

[Chris1956]

Gee, pulling the powerhead and replacing the gasket takes a couple of hours. It is now April. Why wait 6 months?

 

[Waverider17]

Gee, pulling the powerhead and replacing the gasket takes a couple of hours. It is now April. Why wait 6 months?

I'm on my mooring now for the season and would rather avoid starting something that could bite back if anything's corroded on, which I suspect it would be being a vintage motor. I dry store my boat at home over winter which is when I prefer to carry out any overhauls with more time, under cover and my workshop equipment to hand.

 

[Faztbullet]

Just needs #9

 

[Waverider17]

Thanks for everyone's input on this, I've been through my manual to understand the power head removal part, but I can't seem to find any reference to engine mounts, would any of you happen to have this information, and I ow why it's omitted from a repair manual?

 

[Chris1956]

Engine mounts do not have anything to do with exhaust leaks. They may be bad, but it is unrelated to the exhaust leak.

Service manuals only devote a few pages to the midsection, as those repairs are relatively rare. Push and pull on the powerhead and see how much movement is in the mounts. If movement is excessive, you should change them out.

Sierra usually makes aftermarket mounts for about 1/2 price of OEM. Make sure you match the size and grade of the mounting bolts.

Generally, mount bolts are grade 8 steel. On my 135HPV6 Merc the top mount bolts were 7/16, grade 8 fine thread steel. The lower mount bolts were 1/2" grade 8 fine thread steel. All use nylon locknuts and washers.

I have found that the bolts corrode into the mounts, so you need to replace both.

 

[Waverider17]

Engine mounts do not have anything to do with exhaust leaks. They may be bad, but it is unrelated to the exhaust leak.

Service manuals only devote a few pages to the midsection, as those repairs are relatively rare. Push and pull on the powerhead and see how much movement is in the mounts. If movement is excessive, you should change them out.

Sierra usually makes aftermarket mounts for about 1/2 price of OEM. Make sure you match the size and grade of the mounting bolts.

Generally, mount bolts are grade 8 steel. On my 135HPV6 Merc the top mount bolts were 7/16, grade 8 fine thread steel. The lower mount bolts were 1/2" grade 8 fine thread steel. All use nylon locknuts and washers.

I have found that the bolts corrode into the mounts, so you need to replace both.

I've been down to my mooring this morning and rocked the power head but movement is minimal. When I lift the power head I'll just go ahead and replace both engine mounts and any gaskets and I'm sure a few other parts will want replacing along the way. I suppose it's to be expected from a 35 year old motor but I'm going to tackle it seeing as I've completely overhauled the fuel and ignition system recently.

 

[Chris1956]

You will want to source the mounts and bolts before taking anything apart. The mounts look to be hard to get.

 

[BWR1953]

Here's one source. My mechanic basically told me to get pretty much anything to do with the job because it's 40 years old and likely to be grungy/corroded and stuck. He mentioned that it's possible that the bolt heads might snap off.

https://www.marineengine.com/parts/mercury_marine_parts/sn/06589696/ 1050625/275_140