Yamaha 25 3 Cylinder

[boben1968]

I have a 200 Yamaha 25 3-Cylinder. Had motor apart new lower unit seals, bearings, and complete new water pump. I had 40 carbs, and tuner work done, carbon fiber reeds. Repainted motor put back together ran on hose for 30 minute. Idled good and good water flow. Took to river for a test run. Ran good 37 MPH at 6000 RPM on an Xpress 1546. Slowed down to an idle noticed my High Temp light flashed and motor tattle tale was slow and motor would not idle good. Got home dropped lower unit water pump all looked good. Ran motor on hose would not idle and ran hotter than normal. Pulled T stat and it was wide open. Pulled spark plugs and found water. Pulled head and gasket was bad. Also pulled the exhaust cover to check for corrosion and or pluggage. Had head checked at local machine shop and took a 0.005 skim. Put motor back together with new gaskets and still runnin bad and not getting water flow from tattle tale. Pulled plugs and looked damp but not water drops like before. I haven't pulled head back to inspect yet but I think maybe the head is not true / flat or maybe a bad block. Anyone here have this issue? Thanks...Please e-mail me at bobby.crochet@lyondellbasell with any info....

[jldsc]

possibly a powerhead to midsection gasket....but what you've already done is what I would have done too....maybe a corroded water tube somewhere in the midsection....just a few ideas....


Sent from an Apple Tree..

[CajunChristian]

I have worked on a couple of those motors that had cracked base plates. Had 1 with a cracked exhaust pipe, it allowed water to be drawn back into the exhaust ports of the motor. Have seen a couple that the hub on the impeller was spun, pumped great at idle, would not pump at WOT, but that would not cause wet plugs.There are several possibilities, none that are easy to diagnose. After what you have done, disassembly is the next step to diagnosis. The problem can be diagnosed, but not over the internet or phone
D