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1999 Mercury 125 2 stroke Outboard throttle issues

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StevesLX

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So we just test drove a 99 pontoon boat with a Mercury 125 2 stroke outboard. It took a minute or 2 and a lot of cranking to get started. The guy had to squeeze the bulb about 10 times or more on 2 different occasions and then it started. A lot of blue smoke for a little bit and then it went away. The boat seemed to idle fine. We idle out of the no wake zone and off we went. I noticed he would gradually bump the speed and hold it there for a few and then do it again and hold it there and do it again and so on. The motor sounded good and seemed to run fine. We went about a mile down the lake total and then we slowed down and turned around. The guy never did go back up through the throttle then. He kept it part way and the motor would throttle up and then come back down all by itself and it would do this back and forth until he would move the throttle lever forward more. Then it would start doing it again. He then tried to just go straight forward with the throttle to WOT and it wouldn't throttle up. It acted as if it was going to stall if he didn't pull back on it. A few times it would sputter also. So before I go and drop $5000.00 on this thing I would like to know if I should run or is this a simple fuel issue or spark issue or what? Any help would be appreciated.
 
Sounds like a fuel issue or multiple fuel issues.

First off he is selling the boat, so it's not perfect - if it was it wouldn't be for sale. Second, he is selling the boat - that tends to indicate "unused with little to no routine maintenance".

Based on the symptoms it could be 1) clogged carbs (lack of speed, hitching, gagging, having to pump it up to get fuel ultimately to the cylinders), 2) bad, old fuel lines that need replacing 3) old gas in a motor that wasn't (winterized) when it was last laid up 4) bad fuel pump 5) crud in the gas tank, bad vent, toasted anti-siphon valve, clogged pick-up or 6) clogged fuel filter - and that's just the first half dozen things that come to mind.

Probably a new set of spark plugs, a water pump service and gear oil change would also be in order.

What might it cost if you need a dealer to address all the possible issues?

If the carbs need cleaning and rebuilding count on $750 plus parts - will kick the snot out of almost a grand there if you add in a fuel pump rebuild.

If it's just the tank/lines they might be easily cleaned up/replaced for a hundred bucks or so - if it's a built in tank with issues, keep throwing 100 dollar bills at it until it's cured.

Servicing the lower unit including the water pump and gear oil should be about 200 bucks depending on what parts you need - somewhat less if it was done in the past few years.

Other little odds/ends usually bill out at about 100 bucks an hour, plus parts (sparkplugs, carb adjustments etc), 1 hour minimum.

To truly determine if the price for the "whole package" is fair you need to put a fair value on the boat itself, any trailer if included and then the going price of a fully tuned 1999, 125 Merc. From there I would deduct about a grand from the motor value to address the issues you note.

If that come out at or above the 5K he is asking, then it's still a good deal - as long as you fully realize that you may need to put another grand into it before it's seaworthy...
 
I am not great with two strokes but I own this motor and have been around boats all my life so I'll give my 2 cents.
This could be a whole lot of different issues ranging from very inexpensive right up to throw the motor away and start by bolting on a new outboard.
Mine has been a solid performer but I have maintained it thoroughly!. Lots of gear case oil changes. Lots of fresh fuel. I never store with un-stabilized fuel. I fog mine at the end of the season. I use a fuel pre-filter to remove water and particulate etc. Back to your application.

Might just need a fuel filter.
Might just need a set of plugs.
More likely it needs at least All four carbs cleaned and or rebuilt They have to be synchronised which requires some tuning and a manual.
If the previous owner ran ethanol blended fuel the carb bowls could be rotted out and it may need four new carbs.
the boat could have sat with ethanol fuel and you may have a complete tank of stratified garbage fuel and water ethanol mix which will dissolve metal fittings including aluminum tanks.
If it has been running poorly for long it could have one or more cylinders running in a lean condition which will destroy your rings and cylinders.
What is the compression? Could be serious issues here too.
It's been a long time since I was in my carbs but as I recall this motor runs on two cylinders at idle and only fires up four when it hits a certain rpm 2,200 ish? Mine shows a marked difference when the four cyl all fire up. Its not smooth on the throttle but just the one substantial power jump when they all light up. It has done this since i bought it 14 years ago.
I use my primer ball once a year to prime the pre-filter after I change the filter. After that it starts flawlessly with a brief application of choke. 2-3 seconds max.
Mine is stinky, it's loud but it gets the job done and it's not too bad on fuel.

This could be a huge can of worms and a $5000 repair cost at the dealership is not out of the question.

If you are not mechanically inclined DO NOT buy an old boat and especially DO NOT buy a broken old boat.
I would highly recommend a pre-purchase inspection if you are not a mechanic.
Consider asking the buyer to get it running right before the sale.

Good Luck but get some answers before you buy it!

Jeff
 
Well this guy did tell me that he failed to use in stabilizer in it. We live in Ohio so we don't boat year round normally. He did say he pulled it out of the water and put it in storage but no real WI terization done. He said the boat is not his top priority. He did say this problem started last year. I drag race and build race motors and trans so I am mechanically inclined but I have never messed with boat stuff.
 
10-4 I'd do the compression test for sure. Just in case it was leaned out. Check the plugs too. if you have a bore scope check inside. look at how easy it is to access the fuel tank. Mine for example requires cutting out the floor if it fails. Bank on siphoning and cleaning the tank. There is lots of info on the forum on ethanol and phase seperation. Long term I would suggest a fuel pre-filter with a spin on cartridge. I would also open the bottom gear case screw and see if there is water there. It should be should be clean clear gear oil maybe blue maybe gold. If there is water or emulsified oil and water it could be trouble. You don't need to let much out and the vacuum will hole most of the oil in unless you open one or both of the vent screws. I rebuilt my leg with all new bearings and seals over the winter. Bank on a couple hundred dollars if the gears are still good. I cross referenced most parts and bought them for about 1/2 price at my local machine shop.

outboard carbs are not hard to rebuild and clean as long as they have not been eaten up by ethanol and water. Maybe pull an easy one and open the float bowl.
Consider a full set of fuel hoses too, How accesable are they? Not a lot of money but on my boat they are VERY unpleasant to work on with dark remote stretches full of glass fibers.

A four stroke is a LOT more pleasant. The exhaust stink on mine is unpleasant for tubers and skiers. I wish I had a four stroke but it has been very reliable for me for 14 years.

Good luck with it!
 
I would do compression test followed by a thorough spark test and go from there with carb removal as Jhanratt suggested.
 
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