Tweet
Loss of power under load? An answer?
Hi guys, I have been wrestling with my outboard for a couple of months now with help from a mechanicaly inclined mate. The outboard starts first time only using a quarter of the pull rope, idles fine and happily s*****s along at a gentle *****ing speed, the odd backfire nothing major, rough running occasionaly but then smooth again. In the tank in neutral - absolutely fine, rev the b@@ls off it with no issue. But when the throttle is increased up to planing speed, well it doesnt reach planing speed! Starts running really rough and vibrating, the more gas you give the less power you get until it stalls out completely. This has just got worse every time I have run the motor on the boat (Avon 4m RHIB), when first bought, I could plane the boat and the problem would only occur after 3/4 throttle, now after a couple of months it won't plane at all. Checked fuel system and cleaned carbs, checked compression - 115 psi cylinder 1, 125 psi cylinder 2, checked spark - nice bright spark on both cylinders, checked timing, checked this and checked that blah blah, no sign of the cause. So maybe a final carb clean? Carbs were taken off and they were totally clean, jets, floats, everything clean but we cleaned them anyway. My mate wanted to look at the reeds just to be sure because his dad had similar issues with an outboard which turned out to be caused by the reeds being corroded. but they looked fine they were shiny and clean, one reed was a mouse hair up on one corner but almost impossible to tell so we decided they were fine. My mate put the reed plate back on and we were about to replace the carbs when as an afterthought he started turning the flywheel to listen to the cylinders, they sounded different, while putting his ear up to the two reed intakes he noticed why they sounded different! Top cylinder was sucking in fine and sounded like a piston under pressure in a cylinder, bottom one was fa@ting out air through the reeds and back into the carb. We sprayed wd40 on both sets of reeds just to make sure and the top one sucked it through the valves bottom one sucked and then blew oil back out. I guess this was why we found oil in the bottom carb from the auto mix nozzle which is between the carb and the reeds, that oil should only be going into the engine and never back into the carb right?
Sorry for the long winded story but I wanted to put all the details down that I could think of in case anyone else is having the same problem and may not have thought of the reeds as a cause. Also I wanted to describe in detail how we found the problem - take spark plugs out, take carbs off, turn the flywheel in it's operating direction (clockwise in my outboard) and use your hand over each reed valve intake for a couple of turns of the flywheel to feel for air coming back through the valves, also , listen for hissing of gasses escaping through the reeds.
I guess I wanted opinions from the experts too, are me and my mate right in thinking this is the cause of my problem? Are we correct in thinking that air should not be going the wrong way through the reeds? We discovered this despite the reeds appearing clean and undamaged, maybe the rubber was worn slightly where it seals the reeds. I'm going to buy 2 new reed valve assemblies which are not expensive and I'll post what difference there is if any. Am I barking at the wrong delivery man though? Your opinions and thoughts would be greatly appreciated. Thanks Guys
Sorry for the long winded story but I wanted to put all the details down that I could think of in case anyone else is having the same problem and may not have thought of the reeds as a cause. Also I wanted to describe in detail how we found the problem - take spark plugs out, take carbs off, turn the flywheel in it's operating direction (clockwise in my outboard) and use your hand over each reed valve intake for a couple of turns of the flywheel to feel for air coming back through the valves, also , listen for hissing of gasses escaping through the reeds.
I guess I wanted opinions from the experts too, are me and my mate right in thinking this is the cause of my problem? Are we correct in thinking that air should not be going the wrong way through the reeds? We discovered this despite the reeds appearing clean and undamaged, maybe the rubber was worn slightly where it seals the reeds. I'm going to buy 2 new reed valve assemblies which are not expensive and I'll post what difference there is if any. Am I barking at the wrong delivery man though? Your opinions and thoughts would be greatly appreciated. Thanks Guys
Comment