frustrating as hell out on the bay last weekend-yamaha f150 outboard starts fine cold, idles smooth, but as soon as i punch it past 2500 rpm, it bogs down hard, like it’s choking on fuel. black smoke pouring out, no power, had to limp back on one engine at half throttle. thought it was classic fuel starvation or clogged carbs.
first thing, checked the obvious: fuel filter clean, primer bulb firm, no air leaks in lines. swapped the inline filter anyway. marina buddy swore it was the vsts (variable speed something throttle? nah, vapor separator tank) getting clogged with ethanol crap, so i pulled it apart-nothing but clean fuel. online forums screaming “reeds” or “low compression,” so i yanked the plugs (fouled but not dead), gapped ’em fresh, even ran seafoam through twice.
towed it to the shop monday, $800 later? turns out the damn ecm relay was intermittent-tiny corrosion on the pins from salt spray. they cleaned the contacts with deoxit, reseated it, and boom, rips to wot no problem. insane how a $5 relay socket kills your whole day on the water.
tip for anyone with yamahas: before tearing into carbs or injectors, yank the ecm fuse/relay and inspect those pins under a magnifier. spray with contact cleaner religiously after every salt trip. game-changing if you’re solo-saves a haul-out nightmare. anyone else seen this on 4-strokes?