Loss of Power

[Wavey Davey]

I bought a used boat and tried it out for the 1st time.

It ran OK at first, but after a while it lost power. It started and ran, but with the throttle all the way down it would not go wide open. It's a 1994 Mariner 90hp 2-stroke

with oil injection. I'm looking for any help or suggestions on what the problem could be. I'm going to put in new spark plugs, fresh gas with Seafoam and see if it helps.

[marine_man]

Does it sound like it's trying to get to WOT, but boggs down? Or, does it seem like moving the throttle lever doesn't do anything?

If it's more of a bogging type of issue doing what you're planning on doing will probably help, but may not be enough.. do you know the history on the motor? Was it wintereized? Was there fuel stabalizer added to the gas? If not you might be looking at a carb cleaning... but try what you've got planned first. One option would be when you hit WOT and it doesn't do much.. then hit the choke - if the motor picks up then the engine is starving for gas and is likely in need of a carb cleaning.

Gas doesn't last very long anymore before it starts breaking down...

marine_man

[swampman]

If it has'nt been used for awhile I would guess that your carb might need to be cleaned, had the same problem when I bought my boat ,did the same thing started fine , idled ok but at full throttle I had about half speed. also make sure the bulb is'nt collapsing in your gas line. could be alot of things but I still would guess carb.

[Wavey Davey]

Marine Man, what do mean by "WOT"?

I don't know the history of the motor. I don't have the owners manual for it either. The boat has a built-in gas tank which was 3/4 full from last season. I don't know the fuel capacity of the tank but would guess around 15 to 20 gallons. That's a lot of old gas...

[TommyJ33]

also....check to make sure your gas vent is open!

[TommyJ33]

drain the old gas an put it in your truck.

Add new ethanol free gas with a heavy concentration of sea faom. Run 5 gallons worth then add more gas. should clean up the Carbs. if not, take out the carbs and clean em up.

oh and make sure you change the oil with new quicksilver 2 cycle oil injector brand oil.

[FRESHWATER PETIE]

Maybe over heating?? If so, the impeller might be bad or clogged. Does it start fine after its cooled down?

[marine_man]

WOT is wide open throttle...

marine_man

[Wavey Davey]

I don't think it's overheating, impeller spits out water strong. I thought about the vent on the fuel tank, that would explain the problem, but there isn't one. This is the first boat I've owned with a built-in tank. The gas cap doesn't have a vent. Maybe someone who has a boat with a built-in tank can shed some light on this. Thanks for your replies, it's going to be Saturday before I can check things out again, the boat's up north.

[upnorth]

Sounds more like vapor lock. Be sure your venting it working. Check to see if the fuel bulb is collapsing. If it is you are not venting correctly.

[marine_man]

It could be a fuel delivery problem... try this next time (in addition to the choking method I explained above) when it happens, have leave the motor at WOT and have someone squeeze the primer bulb... if the motor picks up it's likely a plugged fuel filter (not real likely) bad primer bulb (somewhat likely) or a weak fuel pump (somewhat likely).

Built in gas tanks have vents as part of the filler neck... they used to have the vent on the outside of the boat, but the trend recently has been to vent the tank back to the filler neck, presumably to head off envrionmental issues from fuel coming out of the vent...

marine_man