Just out of curiosity...-gctid821342

[simbad]

When I start the engines on my 5788. I get a pretty large air expulsion from the aft side of the boat. Imagine what seems like a big bubble of air thrusting out from the water. I think it's lined up with where the water pickup is so my assumption is this is air in the pick up that some how gets blown out when the water pump starts.

I don't see any issue I've just never noticed it on any previous boat, but also never had a boat with such massive engines

Do you think that's what it is or is there some other simple thing that i'm totally missing.

[Relationship]

The 52 and 5788 have underwater exhaust.(That's why they are so quiet) What you are hearing/seeing is trapped air in the exhaust being forced out upon the starting of the engine(s). Those HUGE exhaust ports you see in the engine room dump out on the bottom side of the hull underwater. Only a small portion of the exhaust exits on the small ports on each side of the hull.

[simbad]

Ahh that makes total sense now. I had t thought of that. Thanks for the answer!

Does it just exhaust the gases underwater or does a portion of the raw water also go through the underwater exhaust and a portion through the rear thru hull above water?

[Omega]

The exhaust on each engine has a HUGE main underwater exhaust port that exhausts both gases and water and a bypass exhaust that is about 2in that exhausts above the water. The bypass exhausts both gases and water, as well...

[simbad]

That makes sense now I ever thought I was getting quite as much cooling water out of the above water line exhaust now I know why.

Thanks