Fish 0 Posted March 13, 2018 Share Posted March 13, 2018 My production boat has extractor fan fitted as standard in the engine room. The original Jabsco unit recently died so I replaced it with a identical TMC 4” in-line blower but after 3hrs use the fan blade flew off. A few days later Burnsco swapped it another TMC (on the advice that TMC is normally good kit) but exactly the same thing happened to the new unit after 30 mins. So I returned it for a refund and will never buy another item if TMC kit again. So stick with Jabsco is my advice although as someone else said they are all quite noisy. That is a bit marginal on Burnsco's part. I had a good look at those TMC units and have a 3" one in the shed. They aren't rated for continuous running. They are designed as bilge blowers. The application is for gasoline engines (i.e. in the States) to blow explosive fumes out of the boat before starting the engine. They are design to run for 30 sec - 2 min, thats it. Its all written in the manual for the blowers, either in the box or on line. Not at all surprised you had two last as long as you did, that is all they are designed for. Quote Link to post Share on other sites
Fish 0 Posted March 13, 2018 Share Posted March 13, 2018 Interested in knowing where your engine sources it’s fresh air intake from. With the older style set ups, and with a bit of sound proofing, they should just suck cold air up out of the bilge. Generally there is enough gaps and holes under bunks and around floorboards to allow air into the bilges. I have set up an blower fan inlet, along with a baffle to supress noise break out, but I also set about sealing the whole engine box with sound proofing. Engine is now quieter than the drive train (grrr, need to look at that). Quote Link to post Share on other sites
Fogg 427 Posted March 14, 2018 Share Posted March 14, 2018 I just presume that there are enough natural sources of fresh air ingress from a combination of the 3 removable engine panels (front, back & side) plus bilges. I recently did a test at WOT and the engine ran 100 over it's stated maximum of 3000rpm and sat there happily driving us pretty fast with no sings of overheating, shortage of air or any other problems. Whilst there are many disadvantages to production boats, they also have big advantages like having 1000s of similar boats running similar systems and so if there is a fundamental design problem it has probably either been sorted by now or at least made public e.g. the owners forum. And I've never heard of any problems with engine room aspiration on our boat hence sticking with the factory set-up. Quote Link to post Share on other sites
Island Time 1,220 Posted March 14, 2018 Share Posted March 14, 2018 Aleana, just remember that many engines tacho's run off the Alternator - and are regularly wrong! Sometimes by a lot. Check it with a proper calibrated tacho before changing anything! Especially for prop calculations etc.... Quote Link to post Share on other sites
BNG 44 Posted March 14, 2018 Share Posted March 14, 2018 Stop guessing and do the rough calculation - Swept volume of engine - lets say 2L x engine revs at cruise (say 2000rpm) - 2 x 2000L = 4000L/Min or 4 cu/m/min This assumes 100% volumetric efficiency which isn't possible but will get you close enough. I was recently on a Fjiordland based cray boat, you couldn't open the engine room door at cruise rpm due to the vacuum....and if you did it was about 50deg C inside through lack of ventilation. And then the muppets expected the intercoooler to cool the air to get anywhere near efficiency... where a bit of ventilation would have helped on all counts. Quote Link to post Share on other sites
wheels 543 Posted March 14, 2018 Share Posted March 14, 2018 And as BNG has calculated, 4 cubic Metres of air per Min. That is going to take one hell of a Fan to provide. If you ever wonder about the engine not getting enough air, look around the edges of hatches that have carpet over them. (more common in Launches) and you will see the soot around the edges of the hatch. Quote Link to post Share on other sites
SloopJohnB 323 Posted March 14, 2018 Share Posted March 14, 2018 should be a correction factor for been a 2 or 4 stroke Quote Link to post Share on other sites
Fogg 427 Posted March 14, 2018 Share Posted March 14, 2018 Turns out my engine room has an air intake duct the same size as the extractor fan duct. So my extrator fan is helping the engine breath by sucking fresh air in through the ventilation duct. It also helps vent general engine smells and when I was running the engine with the extractor fan broken for a brief time I noticed a difference with more engine smells around the companionway area. These have gone now with extractor fan replaced. Quote Link to post Share on other sites
Zozza 293 Posted March 16, 2018 Share Posted March 16, 2018 Oh right. So we aren't talking about what Stormy Daniels said to Trump. Quote Link to post Share on other sites
Priscilla II 392 Posted March 16, 2018 Author Share Posted March 16, 2018 Nah,Stormy told me last nite after dinner it’s fake news. Trump can’t do either. Quote Link to post Share on other sites
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