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C90 Power Loss at Full Throttle

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stoney1356

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"I’ve got a ‘99 C90. I took i

"I’ve got a ‘99 C90. I took it out the other day and while it was wide open, it felt like it started choking for gas, so I dropped the throttle. When I pushed the throttle up it felt like it was going to get up and go, but as soon as it got up around 20k it did the same thing, and just hovered around 20k. I powered down, and thinking that my gas gauge was wrong, poured in 6gal’s of fresh fuel then tried again. It fired right up and rev’ed back up to the normal 35k, then only minutes later dropped again. I ran like this for a good 10min thinking that it’ll blow whatever was choking it out, but nothing. I took it out again yesterday and it started running fine, but went down hill from there, with the day ending with us limping home. When out of gear, I can push it all the way up to 40k.

I cleaned out the fuel filter today and hopefully (weather permitting) I’ll be heading out tomorrow, to see if that fixed it.

Anybody have any suggestions?"
 
"When i took it out over the w

"When i took it out over the weekend to test out some ideas i hooked up an external fuel tank to rule out a bunch of things, and it was still had issues.

What's strange is the fact that it comes and goes...it'll run fine for about 5min, then it'll bog down again until i let the engine sit for a while.

I finally got fed up and brought it up to the boat mechanic and he seems to think it has to do with a water temp valve being stuck. Saying that when it heats up, it's not letting the correct amount of water through the engine, and as a safety feature it's cutting the throttle back.

I've got my bet on the CDI (feels like electronics to me...with it being so erratic).

So i guess we'll see...should have it back by this weekend. I'll post what he finds out."
 
Talked to my dealer today. I h

Talked to my dealer today. I have the same problem on a 50hp. He said it was probably the cdi but there wasn't a really good way to test it. My luck
 
"Just got the boat back...i&#3

"Just got the boat back...i'm not exactly sure on the exact problem (i'm no mechanic) but they said that the 'ball valve' (i think) on the gas line was dirty. Something about a mercury rating of 7 when it should max be 4...make any sense? Something about it being starved for gas when it needs it at high speeds. They cleaned it(?) and took it out and ran it for awhile and couldn't get it to happen again.

As soon as the weather clears up (cold, windy and rainy...i love winter!) i'm going to run it hard to make sure that fixed the problem.

The DT's are starting to set in from not being out on the water so hopefully she's running like a charm!"
 
"I have a yammy 150 2/s (

"I have a yammy 150 2/s ( o4 )done 350hrs , mostly trolling out wide . Lately she has developed a problem .......We cruise along nicely in calm weather and then when it gets rough or we get a little air the engine dies down to about 1/2 revs. Not a good look crossing a treacherous bar , just one of her little moments ! Has been in to the doctor with a glowing report on cylnders , compression etc. I have recently changed the diaphrams on fuel pumps ( there was a little build up on these ), plugs , fuel pump and re-inspected the fuel.......200l underfloor tank. I wouldnt mind so much if it only happened in calm weather or if we stuck in close to shore . Mechanic guy said it would just be a matter of eliminating all possibilities ?????? I know little about mechanical stuff but for a mechanic to say this, humph !!!! What next ?"
 
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