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Inboard gas boats ventilation system11/12/2023 ![]() Also, even if your boat is diesel it should have blowers for extra safety and ventilation of fumes. ![]() Even if your boat is older, it still must conform to USCG minimum ventilation levels, and may require a bilge blower to satisfy those guidelines. The Coast Guard stipulates the use of a mechanical ventilation system for all non-open type boats built after Jwhich run on gasoline. Anyway, I follow it.A bilge blower is important not only because the USCG may require it, but also because your life may depend on it. So I can see some reasons it may be good advice. These engines are happiest at cruise speed, not idling. Also, idling while anchoring means no natural air flow through the vents, none of the huge air exchange from the engine itself and reduced water flow through the exhaust system. Why? I'm not so sure except that after a long run everything in that engine compartment- spare oil, spare coolant, extra engine parts, hot water heater are all hot! so it doesn't seem a bad idea to cool them down. Also my Yanmar mechanic expressed pretty much the same. Yannis-I can only quote my brother, a professional yacht builder and has more practical marine experience than I will have in 10 lifetimes. But even if they were not cooled down, what could the problem be? Is there any reason the engines should be cooler than what I explained? Thanx. So, I understand, the engines are cooled down. What’s the problem with cooling down the engines? When entering any port, you have to slow down anyway for at least 5 minutes, or so.Īlso, by the time you drop anchor, get the ropes, maneuver etc, that’s easily another 10 minutes at idle. It is turned on automatically with the port engine. ![]() I removed the ducting that reached down into the bilge and use them to cool the engine boxes after a long run when the engines are shut down. Yannis-Consider retaining the old gas engine room blowers. A link to a good article discussing diesel air ventilation is below. My 315 hp engines use 776 cu ft per minute at WOT which requires about 115 sq in unrestricted ventilation. Soot buildup decreased by two thirds and I don't have to scrub the transom every time I'm out for more than a few hours. Restricting air (or fuel) flow to the engines will put the mix out of balance and result in poor performance.Ĭaptain Patrick felt that there was enough air leakage through the deck seams and bulkheads to supply the engines but it just didn't seem to be there for my boat so I installed a pair of Vetus SSV150 vents in the inboard sides of the engine boxes down low in the companionway. The long time diesel mechanic who takes care of Amberjack's Yanmar 6LP's explained to me that modern diesels get their increased horsepower per cubic inch by forcing more fuel and air into the combustion chambers and that this is a finely calibrated function. With that being said the forward facing cowl will take in water in bad weather and rough seas, but when it rains the water does not enter if the clam shell vent is attached to the gunnel properly.Įarly on Amberjack had issues with soot buildup on the transom, more than I considered to be normal diesel behavior. Yannis to answer your question of why not, you have to make sure that water is in some way restricted from entering the venting. For those years that was less of a toe kick. Some of the earlier 31's (not sure on the 28) there was a forward facing cowling mounted on the pilaster right at the gunnel. There are other ways to do it but that seems to have been the standard in the marine industry.Īs you will see about 3/4 of the way down, the ABYC recommendations spell out what most manufacturers follow. ![]() The forward facing vents are to force air into the bilge area as the boat is running so that any fumes would be theoretically pushed out the two rear facing vents. Then the two more set more towards the stern, unless the boats were built for diesels. Usually placed right about where the pilaster to the bridge sits. On 99.9 % of the inboard gas engine boats this would have put a clam shell vent on port and starboard facing forward. That requirement means that some type of ventilation has to be installed. I would have thought that all the boats built in the US or destined for sale in the US were built to Coast Guard requirements.
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