Revspan

Hi all,
We all know that the new engines with cats generate a lot of heat. Cram them into a small space and things get even worse. In my 292, I have 6.2s with cats, and during hot weather, the engine compartment gets really hot. Steady state at the TB is around 145-150 deg when cruising at 3800 rpm.

This weekend I plan to do a test by lifting the hatch a few inches and drop on some spacer(2 x 4 most likely) to see how much I can reduce temps. I am confident that if you add ventilation that it will improve....just a matter of how much. When you look at the ventilation system on the 292, it is pretty puny. Maybe a 5"x2" hole in each side as in intake, and a 1" x 6" slot as an exit. my thought is that all air coming in simply has to run over the cats, or heat exchanges(the boat has closed cooling), to get to the TB. It is definitely hot by the time it gets to the TB.

It does not seem that there is a restriction in air to the engines, just a temp issue.

Any specific ideas for getting more air into the engine compartment? Only thing I can think of now is to find some type of hat for the TB and run a duct to a place somewhere near the air intake. Not sure about fiberglass modifications etc.

Thanks!!!

stlliberator

iTrader: (1)

I always leave the blowers running on my 311 and always have on all my boats. I guess it kinda always forces more air into the engine compartment. Not sure if it lowered temps or not. Also I always crack my hatch when stopped at a dock to let some hot air out. Anything short of adding scoops to your hatch won't really allow air into the hatch, plus just bring air in isn't always good enough you have to have a way for the hot air to escape..

endeavour32

iTrader: (4)

I have a long thread about this very issue on my 292 SR-1 in the general Q&A section. With my 650 Hp 509's I gain 200 RPM's and 5 MPH with the hatch off. I'm going to be doing some testing this weekend and posting what works.

SB

iTrader: (1)

Remember, your engine's are air pumps.

The only time a bilge blower is going to pull in more air than the engines is during idle and very low speeds.

Say a bilge blower moves 100cfm or so of air and an engine moves a min of 200cfm of air when just on plane, and 600cfm of air at top speed, which pulls in more outside air ?

So, I present, the real issue with too hot of air in engine compartment is too much of a restriction of air from outside of boat to inside of the engine compartment.

There is more too this of course - vent openings in high pressure area (wind) and vent's in low pressure area (lower psi than atmospheric- measured as vacuum) but in simple terms, the answer seems pretty clear which will exchange more air.

Revspan

All true, and I will be doing some testing too. My current idea is to cut a hole in the beauty cover of the engine(remember they are little SBs) and run a hose to the air inlet on either side of the boat and then dump the air that is coming into the engine compartment right on top of the flame arrestor..and under the beauty cover. The idea is that I would use brake duct hose(4") so it would be safe, and then I will be able to optimize the situation. Meanwhile, I will try and run with the hatch up a little this weekend and see what happens. Thanks for the ideas so far and I will be back with some data.

GLENAMY 242SS

iTrader: (1)

If I am reading right, you are trying for a variation of "Ram Air", if so I would keep in mind water from washing, spray, etc. where it will end up.

SB

iTrader: (1)

No, the 'beauty cover' is the plastic cover on top of the engine in an attempt to make it look better from the OEM's.

Ram Air is not going to happen at most boat speeds. He is just trying to source ambient air.

I'd use the sides of the rear bench - no water intrusion possibilities there if off the floor.

COOPS

iTrader: (2)

I have the same boat but an 04 without the cats. I would look also at the arrestors. I adapted a larger 3 inch tall set and picked up a solid 3-4 mph. Those less than one inch tall factory arrestors can't be helping at all. Remember the 6.2s are a common cruiser package.

There are very few performance boats that run small bocks

Revspan

Wow....the speed increase is huge for just taking the arrestors off. The TB has a 3.5" dia OD on it. I looked around for another FA, and could only find a K&N which looks decent. Can you share what you put on yours? Is the TB the same size? I am not in love with the beauty cover....it can disappear if it means better performance. Thanks for the idea.

SB

iTrader: (1)

COOPS did a thread on it a while back. Few yrs ?