Any opinions on the ventilation of the engine compartment. I dont see how the engine gets enough air to run never mind keep cool
I’ve heard tell that making the switch to electric drive solves that problem. Can complicate directional stability though.
It should be keeping cool with the heat exchanger. Isn’t yours water cooled?
As long as you haven’t had any issues with the engine and the air intake filter is clean and unblocked, I’d say you can forget about it. The problem with adding ventilation is that you’re adding holes to the engine compartment, which allow noise to escape. When I repowered a few years ago, I took the opportunity to install new 3" foam soundproofing to the walls in there. It’s well sealed for sound, but not airtight. The only engine noise I get is a nice purr. I wouldn’t do anything to compromise that unless I absolutely had to.
RadioZepher thanks for your reply.
I’ve been thinking more about where the engine is pulling its combustion air from. My engine compartment isn’t sealed, but it’s also not intentionally ventilated. If there’s no dedicated air intake, the air has to be coming from somewhere.
The only obvious source I see is under the drip tray, which is open to the bilge. So, in theory, that would be the route for combustion air. But even then, I don’t see any clear paths for fresh air to enter the bilge itself—it all seems pretty well closed up.
Given that the engine, at 3000 rpm, consumes about 53 cubic feet per minute of air, that’s roughly 0.88 cubic feet per second. That volume has to be coming from somewhere. I’m genuinely curious—on your boat, do you have any passive air inlets, or does the engine simply pull air from wherever it can? Where do you think the combustion air is actually coming from?
I really appreciate your insight, especially since it sounds like you have experience with this setup. Looking forward to hearing your thoughts!
I understand what you’re saying, and the thought has crossed my mind in the past. However, it was designed without any vents because Gary Mull didn’t believe they were necessary for the engine to run properly. If there was an issue with the engine not getting enough airflow, vents would have been added sometime during the 7 year production run of the 36/38. Many other changes were made in the course of building 156 boats—adding side deck drains, raising and reinforcing the floors for a stiffer hull, changing the embedded gooseneck for a bolt-on version—but never anything to increase engine compartment ventilation. I take that to mean it’s something I don’t need to worry about.
EDIT: I realize I didn’t actually answer your question! Yes, I think the air for the engine comes primarily up through the 4" holes that are cut into the fiberglass liner, which allow cables and hot water hoses to reach the engine. I have two in front of the engine (one on either side), and one on the aft end, just outboard of the port rear engine mount.
An interesting corollary to that is that on my 1995 F40/40 last year I had to replace the blower hose since the original one had disintegrated. We traced the hose from the engine compartment blower aft and it just ended at the bottom of the starboard lazarette. It was never vented outside. We checked with someone else who told us that is how they all were done at the factory. We ended up venting it outside at stern on the port side of the transom next to the hand held shower. I thought that was very strange. Perhaps it did not need to be vented outside? Has anyone else dealt with this?