Mariner 50 hp 4 stroke. Exhaust noise and hot spot on exhaust housing about 125mm below engine cover

50hp Mariner 4 stroke. 106 hours. 2002-3 model.

Headed out a few days ago. Engine started fine, idles fine. As I increased the throttle it seemed to develop a different exhaust noise. Best way to describe it would be to liken it to a car with a small hole in the muffler.
Motored for 30mins or so. Noise remained constant and engine performed fine.
When taking boat out of the water I noticed that there was a build up of salt in one spot of the exhaust housing about 120mm below the bottom of the engine cover.
Took the boat out the next day- same noise, same build up.
Checked spot where the salt was built up when rinsing engine. It got quite hot. To the point when water was splashed on the spot it would hiss and evaporate. Too hot to put hand on.

Keen to hear if anyone has had a similar problem or can diagnose.

Kind regards
Bradley

Sure sounds like a leak, don't it. Shouldn't be getting hot on the leg like that.

There is an exhaust pipe on this model, and looking at the diagram there's a single bolt and plate, from the bottom, that holds it in place. So I'd expect that if you pulled the lower unit you'd have access to the pipe for removal/inspection.

It might help if you post your serial number, then we can look up the correct diagram.

HTH..........ed

Thanks for the reply. Ill post serial number when I get home this afternoon.
Kind regards
Bradley

I guess an exhaust leak could explain the hot spot. Hot exhaust gases blowing out against the inside of the leg could heat it up to the point that salt water that hits the outside evaporates instantly leaving a salt build up.

Hotspot is on the starboard side.

Serial number
OT283853
2001
50ELPT

Really appreciate your help.

Driveshaft housing diagram for your motor: http://www.marineengine.com/parts/mercury_marine_parts/sn/0T283853/1F51452YD/7457_220

Brilliant. Thanks for that. Off to the repair shop I go armed with some good information.

Appreciate the help.
Have a great day.

Bradley

After looking at the repair manual Im going to drop the gear housing off myself and inspect the exhaust pipe. Looks simple enough based on the diagram. Instructions do not mention or show a gear linkage that needs disconnecting on the bigfoot model?

http://************/lib/mercury/manuals/40-45-50-BIGFOOT.html#/518

Also no visible gear linkage access points.

Any suggestions?
Thanks in advance.

Cheers

The shift shaft in this lower unit rotates to shift. A splined coupler connects it to the upper end. When you pull the lower unit, the splined shift shaft goes with the gearcase.

Best to have it shifted to Neutral before you pull the L/U. And disturb neither the shift shaft nor remote control lever position while you're working on it. This will ensure the shift shaft splines will properly mate with the upper end upon installation.

HTH........ed

Brilliant. Removing the lower unit was easier than changing a light bulb.
After removing the L/U I then removed the plate that appears to hold the exhaust pipe in place. I have tried pulling the exhaust down out of the housing but it does not want to budge. I even tried gripping with vice grips to give it a little wiggle and a pull. All I ended up doing was damaging (minor)the bottom of the exhaust pipe.
Are thee any tricks to removing the pipe? I have looked at the manual and inspected the motor and there do no appear to be any bolts or other impediments in the way.

Many thanks in advance.

Bradley

More than likely the powerhead needs to be pulled to get the exhaust tuner out.

Thanks for the reply.

Bummer- I was hoping it would drop out of the housing as pictured in the assembly diagram. Oh well. Things never seem to be as easy as they seem. Unless anyone else has some further words of wisdom I shall reassemble and take it to the shop.

Thanks for you time and advice.