Installing Honda GX160 Trash/Water Pump on Boat

[mallo]

Good day
I have a Honda GX160 fitted on to a Trash/water pump, I am planning to fit this as an emergency pump on my boat (I know it sounds a bit mad).
I have found the perfect place for it (high up and in the dry) and I plan to bolt it down and pipe it up permanently ready to go.
The only issue I have and would like some advice on is the exhaust from the engine.
I have a dry exhaust from an existing generator which runs fairly close by, my plan was to “tee” into this exhaust with a valve, could this be a problem?
The existing generator exhaust where I want to connect into relatively cold as the generator exhaust gases have cold water mixed with them and then the water is separated from the gas and the gases go down this pipe I want to connect into and the water goes out the bottom of the boat.
I was planning to fit a valve into the leg if the “tee” to stop fumes and moisture going back into the pump.
The next quandary I have is do I take the existing exhaust silencer off and couple the new exhaust straight onto the engine or do I leave the existing silencer on there and couple the exhaust to the existing silencer. I am not too worried how noisy the exhaust is as it will only run in emergencies, what I am more concerned with is that I don’t increase the back pressure too much.
The exhaust for the generator is 1 7/8” bore pipe and is way over sized, I could do the same for the pump however I dint really want to make it bigger than it needs to be, would anyone suggest a suitable size pipe to make the exhaust. The one currently coming out of the engine and going into the silencer is about ¾” to 1”. I have a piece of flexible stainless steel exhaust pipe, its about 1” and I was thinking of using this and then running it into some 1” or 1 1/8” or 1 3/8” or I could go the full hog and do it in 1 7/8” as the main pipe.
This pipe will get hot and I can either insulate for this or space it off anything flammable and fit a guard where necessary.
The rest of the pipe work isn’t a problem, its just this exhaust I would like to pick the experts brains about.
Thanks for any help you can offer.

 

[Navin A S]

Thanks for your question. In this situation, it would be best to use a flexible exhaust pipe that is the same size as the existing pipe coming out of the engine. This will ensure that you don't increase the back pressure too much and will result in a more efficient running engine. As for the exhaust silencer, it is best to leave it on, as this will help to reduce the noise from the engine. Additionally, you should insulate or space off the exhaust pipe from any flammable materials, and fit a guard where necessary.