Change muffler on 471dd marine any issues

"Hi :got a detroit diesel 4-71

"Hi :got a detroit diesel 4-71 marine diesel ,self aspirated type.The stock muffler was too loud and was rusted out anyway so i put on anew one a 4 in one off a tractor trailer.I don't know what type of engine i was for but the one i took of was 4in and replacement also 4in.The engine seems to run fine with a noticeable drop in noise level....a definate bonus.Is there any issue with me doing this?The old muffler was 1/2 as long as the new one.One can actually stand next to it now while at cruise speed.Any issues with this?"

MAXIMUM EXHAUST BACK PRESSURE

MAXIMUM EXHAUST BACK PRESSURE AT MANIFOLD OUTLET{ FULL LOAD}NOT OVER 4.5 IN HG.MERCURY

"Ok marv thanks very much ,you

"Ok marv thanks very much ,you are a wealth of knowledge.Is there a specific plug to remove to check pressure,and what are problem i might encounter by going over? I noticed a difference from last year in the heat in the engine room is up from last year when i had a 5 in muffler on it ,there wasn't much heat at all in the E.R.I have only run the engine 15-20 minutes yet this year.I'm now worried i may do damage if i run it too much before checking pressure.I intend to use her tommorrow so i will run a 1/2 trottle max just in case."

LOOK AFTER THE MANIFOLD OR YOU

LOOK AFTER THE MANIFOLD OR YOU MAY HAVE TO INSTALL A PLUG IN THE PIPE.

"Checked it out marv with set

"Checked it out marv with set of gauges that refrigeration techs use and couldn't get the gauge to hardly move at full power.I converted 4.5 oz hg to psi and comes out to be 2.2 psi.I am not even getting 1 /2 psi.Also the engine temp in past with stock muffler was 160 ,now its 140-145 seems to run cooler with this muffler.Whats your opinion on it?"

you do need some back pressure

you do need some back pressure to help keep the rings seated and engine should run 160 to 180 temp.

yeah your right on the money a

yeah your right on the money again marv ran it this weekend for 3 hours at full and it was running at 170 .I checked it numerous times and it held there at 170 .I backed her off to around 1500 rpm and it ran at 145 or so.Thanks for prompt reply marv.