Originally Posted by mbevins
If I increase RPM up to 2000 while in neutral is there enough exhaust pressure between the turbo and the elbow to check for a leak?
If "between the turbo and the elbow" you mean the turbocharger exhaust side and an elbow that connects the turbo to the downstream exhaust system, the answer is a qualified yes.
The backpressure developed in an exhaust system has a minimum level that is a product of the size of the tubing, the number and angle of the fittings, the level of water in a lift muffler if one exists, and the overall length of the system from the turbine outlet to the atmosphere. The lowest pressure is developed at idle, the highest at maximum power.
Using a generator as an example since we can easily see the difference created by load changes that occur at the same rpm, a system might have a no load backpressure of 13 or 14 inches of water column (~34mB) to a full load backpressure in the high 20 inches (~70mB) or even higher with a poorly designed system.
Even 13 or 14 inches of water is usually enough to determine if exhaust fittings are leaking.
Don't be so hard on the mechanics. They want to replace the insulation blanket because if you took the boat and ran without it and had a fire that could be shown to be the result of leaving it off, they would be liable. Let them put it on and if you want it off, you take it off so there is no doubt exactly who created what might be a hazard in your engine room.