twin_engine_dadOPSandbar CaptainCoeur d'Alene, ID29 posts, joined Jun 2025
#1
2018 Yamaha 242 Limited S, twin 1.8 HO, 260 hours, Lake Coeur d'Alene. last summer it ran 49 on the GPS with four of us and half a tank. this spring it tops out at 44 and the hole shot feels soft, like it takes a second before it grabs. both engines reach their normal rpm, no alarms, nothing on the dash.
we did run it up the St. Joe last August when the river was low and i heard rocks. so i know what you are about to say. before i hand it to a dealer for two weeks in June, is this something i can check myself, and what am i looking for?
P
impeller_nerdPump GuruLake Elsinore, CA77 posts, joined Jun 2025
#2
same rpm and less speed with a soft launch is the pump, not the engines, almost every time. the engines are making the power and the pump is not turning it into thrust.
start with the cheap stuff. pull the intake grates and look for anything wrapped on the shafts, rope, weeds, fishing line. then put a light on the leading edges of the impeller blades. rounded over or curled from rocks is the classic river tax. if the blades look fine, buy a feeler gauge set and check the gap between the blade tips and the wear ring at three or four spots around, and compare it to your manual. if you lost the paper one the owner's manuals are on yamahaboats.com.
gap way over spec, or bigger at the bottom than the top, means the ring is worn out of round and that is a part. curled blades are a file and an evening.
J
rotax_shop_jenPump GuruOrlando, FL61 posts, joined Jun 2025
#3
listen to pete on this one. one thing from the dealer side if you end up taking it in: ask them to check both pumps and write the measured gaps on the ticket. not "worn," numbers. some shops sell two rings when only one side needs it, and the ring is not a cheap part on these, plus a few hours of labor per side.
and look at the grate itself while it is off. a bar bent up toward the impeller messes with the flow even if the blades are perfect.
T
twin_engine_dadOPSandbar CaptainCoeur d'Alene, ID29 posts, joined Jun 2025
#4
pulled both grates saturday. port side clean, blades sharp, nothing wrapped. starboard looks like a dog chewed it. two blades curled over and one has a nick about the size of a pencil eraser. the gap on starboard at the bottom of the ring is about double what port reads at the same spot.
so the St. Joe tax, with interest. ring is on order, i dressed the blades while i wait. will report back.
S
sandbar_weekendsSandbar CaptainTampa, FL33 posts, joined Jun 2025
#5
the ring is the one part i would not save money on. a buddy in Apollo Beach bought an aftermarket ring online for his SX190, it was a hair out of round and he never could get the gap even all the way around. ended up buying the Yamaha one anyway. paid twice.
T
twin_engine_dadOPSandbar CaptainCoeur d'Alene, ID29 posts, joined Jun 2025
#6
results. Yamaha ring on starboard, blades dressed, about four hours in the garage with my son handing me the wrong socket on purpose. 48.6 on the GPS this morning with the same load as the 44 run, and it grabs right away on the hole shot again. the nick is still there, smoothed out, pete said to run it and stop staring at it.
new house rule, no St. Joe trips in August. my son is not happy about it.
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