Hi All,
I have a 1984 Mariner 5C made by Yamaha. I bought the motor used in 2010. It was previously on a sailboat and left in salt water - it was rough and cobbled together from at least a couple motors (different s/n on block and clamp and lower unit is a spare from yet another 5C). Before putting it in the water I replaced the impeller/housing, rebuilt the carb, had the lower unit resealed and put fresh lube in, painted the motor and installed a fresh spark plug. I dropped it on the back of my inflatable and cruised the harbor just fine for a year or so - Actually surprisingly well for a 28yo motor, but it could never plane out the inflatable (top speed was 6-7mph). The tell tale was present but not strong, but not overly hot either so I was not concerned about overheating. Then one day a month or so ago the motor started running rough and dying at idle. I found that water was getting into the combustion chamber and onto the plug.
I assumed this meant that the wet side of the exhaust was leaking, so I ordered parts from Yamaha and tore into the motor. There were bad salt deposits and corrosion everywhere blocking the flow of water. I cleared the corrosion out as best as possible with a probe and compressed air, and cleaned / polished the surfaces of the exhaust cover, plate and block with roloc pads, only to find the Yamaha gaskets I bought didn't fit. I put it back together with gray rtv and gave it a pull - the motor will not start at all now. I ran a compression check and I am getting a peak of 70psi which seems super low. I tried a fresh plug last weekend and still no go - although I do get exhaust now as I try to kick it over.
I am assuming this means I need piston rings and the real deal mariner gasket set - so I ordered a set of rings and a powerhead gasket kit on Monday and will tackle installing them this weekend. Does anyone have any other suggestions or things to check as I dig into this?
I have a 1984 Mariner 5C made by Yamaha. I bought the motor used in 2010. It was previously on a sailboat and left in salt water - it was rough and cobbled together from at least a couple motors (different s/n on block and clamp and lower unit is a spare from yet another 5C). Before putting it in the water I replaced the impeller/housing, rebuilt the carb, had the lower unit resealed and put fresh lube in, painted the motor and installed a fresh spark plug. I dropped it on the back of my inflatable and cruised the harbor just fine for a year or so - Actually surprisingly well for a 28yo motor, but it could never plane out the inflatable (top speed was 6-7mph). The tell tale was present but not strong, but not overly hot either so I was not concerned about overheating. Then one day a month or so ago the motor started running rough and dying at idle. I found that water was getting into the combustion chamber and onto the plug.
I assumed this meant that the wet side of the exhaust was leaking, so I ordered parts from Yamaha and tore into the motor. There were bad salt deposits and corrosion everywhere blocking the flow of water. I cleared the corrosion out as best as possible with a probe and compressed air, and cleaned / polished the surfaces of the exhaust cover, plate and block with roloc pads, only to find the Yamaha gaskets I bought didn't fit. I put it back together with gray rtv and gave it a pull - the motor will not start at all now. I ran a compression check and I am getting a peak of 70psi which seems super low. I tried a fresh plug last weekend and still no go - although I do get exhaust now as I try to kick it over.
I am assuming this means I need piston rings and the real deal mariner gasket set - so I ordered a set of rings and a powerhead gasket kit on Monday and will tackle installing them this weekend. Does anyone have any other suggestions or things to check as I dig into this?