2001 Mercury 90 hp 2 stroke 3 cyl Bogging

[gydatree]

Hi. I have learned a lot reading these forums over the years, and I am at wits end trying to track down whats causing my 90 hp 2 stroke on my 25 ft pontoon to bog, so I figured I'd post and see what we get from the pros.

So, I bought this boat and motor as a project, tore down the boat to the toons and rebuilt/reupholstered everything. It definitely sat out of the water for at least a year before I got it, and I dont think it got all that much use before that.

When I got it, it would crank and run, though like crap, it did crank and run out of the water. When we were close to finishing rebuilding the boat itself we started to look at the motor. First, I replaced the fuel line with bulb and in line filter, got it to start up, but still sounded bad, so i rebuilt the fuel pump and carburetors and added new plugs. Put it in the water and though it had a rough idle and low speed it got up and ran beautifully across the lake for maybe 4 or 5 trips over maybe 3 weeks.

Not sure if its coincidentally or not, but one day we put ethanol gas in it, maybe 9 people on board and headed out. It started missing lightly on the way out when we would hit waves, and on the way back in it wouldn barely go ver idle speed without bogging. I then rebuilt the carbs and replaced sparks again and secured all fuel line connections. Put it back in this weekend, and at first it bogged when i gave it any gas, but after very very slowly accelerating I got it up to about 15 mph, ran like a dream for a bit, then bog. After re priming I can get it going again and do the same thing.

However, after being out for a few hours, it begins to not want to go at all. I rode for a while with my hand on the bulb and most of the time when it bogged it lost pressure, and with some pumping right when it happens I can keep it going and re prime the bulb and so on and so on.

The battery seems to maintain strong voltage, so I dont think its the stator. I have also replaced the starter, cleaned all electrical connections in the motor (always starts right up and runs no problem), added new battery cables, and changed the gear lube with new seal gaskets. Ive got the carb screws a little over 1 1/2 turns out evenly, no smoke really ever comes from the motor, timing sounds good when it is running.

So, the only ideas I have are:

*When I rebuilt the fuel pump, I didnt add the rubber circular gaskets in the kit as they were not on it when I pulled it out; could it be an ethanol issue where just those plastic gaskets cannot handle the ethanol alone? Would the bulb lose pressure if so?

*The long gold needles in the carbs that run all the way through them permanently and dont move, not the float needle that hangs from the float, leans to the side and touches the inner wall of the nozzle coming up in the middle of the carb on two of them, and it looks like the top one is headed that way. Again, not the nozzle that the float attaches to. It is in the middle of the carb. Could this be an issue? Mercury said it is, most mechanics seem to think its ok, as I see them for sale like that.

* Pin hole leak in the fuel pump diaphram? when I secured all fuel lines, I pressure tested through the pump with it mounted and it was very air tight. The plugs did seem to have oil on then, the old ones had a lot (1st set i put on). I was thinking it was due to having to drive so slow so much) and the bottom one did seem to have more. After running all plugs are hot, letting me know its hitting all cylinders.

* Oil fuel mixture? I could try to bypass the oil reservoir and pre mix the fuel?

*Worst case: Bad gssket in the powerhead? It does seem to let out excessive fuel, it is a two stroke, but it does seem to let out a good bit after running.

Also, when the motor is off it is hard to get the bulb primed if it isnt already. I can see it go through the filter, and seems to not want to make it all the way through it. however, once it is running it will usually prime up.

Any suggestions would be greatly appreciated!

 

[ondarvr]

Forget about just about everything and get the fuel system cleaned again, nothing sounds electrical.

By running the E-10 in a system that may be dirty and have junk it, plus may have never seen it before, you can loosen all that stuff sitting in the tank and lines and clog things up again. Ethanol is a very good fuel system cleaner.

Every component in the motor can tolerate E-10, so don't worry about that.

If you had trouble priming the system with the squeeze bulb, and had to pump it to keep the motor running better, then look at junk in the tank, a bad bulb, air leak, plugged pickup tube, etc.

 

[gydatree]

ondarvr, thank you for your response. We did empty the fuel tank before ever running the motor, though not deeply cleaned or anything, but lifted upside down and emptied. I have no idea if it ever had ethanol in it or not before, but I think the first couple gallons I put in to get it running on the hose might have been. I filled it with non ethanol and some mercury cleaner stuff west marine gave me before I put it in the water, and it ran like a dream through maybe 2 or 3 full tanks. Then, the day we put maybe 5 gallons of ethanol in and headed out, it started with the slight hesitation and eventually to the bog we have now.

I havent visually inspected the fuel coming out of the tank or anything inside the tank, as there does not seem to be any strain in the line from it at all. Although, we did paint the frame of the boat, and some paint chips could have gotten in there when pumping gas as it chipped putting the pump in there. Also, when we filled the tank yesterday, I did notice some liquid getting on top of the tank. Couldnt quite tell if it was water or fuel, but there was something there.

If the tank is that trashed from the ethanol loosening things up, would it immediately start bogging like that right after I air compressed the carbs clean? Would it lose pressure on the bulb when it boggs?

It seems like it loses pressure downstream. I was able to pressure test from the tank up through the filter to the carbs with no air getting through with my finger over the end and squeezing the bulb, and put solid connections on the lines going down the carbs.

When trying to prime the bulb, you can see fuel getting up through the filter, but seemingly sputtering and not making it all the way through. But you can get it started just fine, and it will prime after running a bit. When it bogs, it is not primed anymore, and unless you pump the bulb it will stall, wait a few minutes, re prime and it will run. Also as I said above, after a couple hours running, mostly at low speeds, it will barely run in gear, and the bulb hardly stays primed.

*I know I took the piece of fuel line between the carbs and pump with the filter in it and put my finger on one end and tried to blow through with no air escaping whatsoever. I also held my finger on the port from the fuel pump to that line and tried to pump the bulb with no air escaping. However, when I put that line on and put my finger on the end of it (the end that would attach tl the carb) (couldnt get the connection and tighter) it seemed to maybe be losing a tiny bit of air.

-I feel like Im self diagnosing here as I type, but I know I tested that piece alone and it was air tight, and that port seemed tl be solid as well, and the connection couldnt be any tighter. Guess it might could be doubled up, but it still ran fine just like it was through 2 or 3 full tanks. Blows my mind

 

[DavidMoore]

No Title

So what exactly is happening to the primer bulb.

When running the primer bulb will loose some of its stiffness, perfectly normal. But if it feels empty / collapsing it would normally mean a leak / blockage upstream from the primer bulb.
If this is the case I would be starting from the tank and work my way downstream to look for the problem, first by checking the fuel tank vent is open / not blocked.
Then check the strainer on the fuel pickup and work my way forward.
You can confirm a problem with the tank by running of a temporary portable tank and see if the problem disappears.

If your squeezing the primer bulb and it seems to be filling with fuel nicely but not going stiff or nearly going stiff then losing the pressure then the leak is in the engine, probably the pump.
You can check this too before tearing into things, remove the pipe from the inlet to the fuel pump, plug it off and see if the the bulb will pump up hard.

What do you mean by "I didnt add the rubber circular gaskets in the kit as they were not on it when I pulled it out" you mean the rubber valves marked c in the sketch.
If so I would go ahead and fit those, it's difficult for me to see how the fuel pump would be working without them.

 

[gydatree]

Thank you for your response DavidMoore. The bulb never does feel like its straining (deflating or anything like that), usually it will stay firm once it is firm for the most part, on or off, but when keeping my hand on it while out running on the lake it seems to lose firmness when it bogs, and usually it will stall at that point if you dont pump the bulb, and if it does stall you can pump the bulb and start it right back up. Eventually it will get firm again, but lose pressure and bog after a short period. It is a new line and bulb from west marine, and I have secured the connections going to the carbs as best as I can.

At this point, based on what you guys have said and lots of wondering, I think my next move is to get the fuel tank off the boat, empty and thoroughly clean it. The extrrnal tank test sounds like a great idea, but im not sure I have a spare tank to use for that. Any suggestions on what to do and not to do when cleaning the tank? Im hoping that running some high octane ethanol gas through it from the clean tank will clean out anything still in the pump lines or carbs from one day of running with what we think is a dirty tank after being cleaned and rebuilt etc.

I did as much pressure testing as I could from the tank through the pump/filter to the carbs and all seemed to be good except for what may have been a tiny leak getting to the end of the line going into the top carb, but i checked that piece of line individually and it was air tight, as well as everything else leading up to it. Seemed like an elevation thing or something. Ill check it again, maybe double it up with zip ties, but the tank still needs to be cleaned.

It only makes sense that after going through 2 full tanks of non ethanol and running flawlessly that as soon as we put 5 gallons of ethanol in we start to get the bog, even after rebuilding and cleaning the carbs twice in one month, rebuilding the fuel pump and changing the filter and spark plugs twice. The first filter I pulled off did seem to have crud all in it and had changed color in a short time.

But hey, Ive diagnosed this thing very logically about four times now with no luck so who knows, just have to keep narrowing the possibilities I guess.

Yes, as far as the gaskets in the fuel pump go, when I pulled it off, there were only what would be C or E in the diagram, the white clear plastic one, so I only replaced those when I rebuilt it after the bog started. I went out alone after I did the pump, and after a faint bog at first it went to WOT 2 or 3 times for me just fine, but the next time it was out we were back to the bog. Is it possible that the rubber gaskets had dissolved somehow from the ethanol after having sat for a long time or something?

Thanks guys! Ill be sure to post any results when I have some!

 

[gydatree]

So I inspected the fuel tank today, and low and behold there is a thick nasty dark colored layer of gunk all across the bottom, and you can see where it is slowly coming up, may have seen some floating around. So this week I will get the tank out and either clean it or get a new one and report my results.

Thanks again guys!

 

[gydatree]

Allright, so one more item off of the list that is not the main issue:

I got a new, clean tank and switched it out with the other one. It was to tall to be plugged into the vent and fill ports, so they were left open, just hooked up the fuel line going to the motor. When we first started out, I didnt push it very hard since there was minimal gas and we just rode over to the fuel pumps, but it was running super smooth at a mediocre speed. I put more gas in and headed out, hit the throttle, it responds and sounds great getting up to high speed, but start to bog out again pretty quickly. The only difference now, is the motor is much smoother overall, and when it starts to bog you can pump the bulb and it will stay at the high speed. Before, it would just bog all the way down before you could get it going again.

So, now that I cleared the tank of being any issue besides the fact that the vent and fill ports were left open, it seems there is a loss of pressure somewhere between the tank and the top carb. I say that because when it bogs they all go out at the same time, not any missing or smoke or anything. Like I said before, when pressue testing it did seem like a tiny bit of air may have been escaping at the top of the line going into the top carb.

So, what do you guys think?

*Fuel pump diaphram?

*Missing rubber gaskets in fuel pump?

*Bad fuel pump?

*Double up connections from fuel pump to carb?

*Pressure in tank?

Any input would ve greatly appreciated!

 

[DavidMoore]

The ethanol in the fuel will not affect the rubber gaskets, and the symptoms do indicate a fuel pump problem

My only advise at this time would be to rebuild the pump as the designers intended with the rubber valves and check the diaphragm for holes. When the fuel pump is off also check the pulse hole in the block is clear.

Do you have an anti-siphon valve fitted?
It could be clogged with the debris from the tank. I am assuming all the fuel lines are higher than the tank, if so try removing the anti-syphon valve, if the problem goes away fit a good quality replacement.

 

[gydatree]

It does seem like maybe the pick up and sender in the old tank were bubbled up on the inside just like the original fuel line to the motor I pulled off, as well as clogging from stuff in the tank and maybe strained the pump when it was running strong those first few weeks. Doesn't really explain how it ran without the rubber gaskets if that is an issue though.

I am going to pick up a fuel pump kit and put the rubber gaskets in, as Im not sure Ill be able to re-use the white pins that the gaskets go on once I get them out. Ill also check everything else you mentioned.

Is the anti siphon valve the connector on top of the tank that connects the fuel line to the motor to the pickup inside the tank? The one on it now is new, but I guess I could see if some stuff came lose and clogged it even after I sloshed a bunch of gas around in it before I put it on. This new tank stands much higher than the old one, to high to hook up to the outside ports.

I run the bulb down the side to where its verticle on the side of the tank, and the point where it connects to the motor is mostly a downward path for the line. From there it goes upward to the fuel pump and then further upward to the filter and top carb, which I dont think is higher than the tank. Should the bulb be kept up higher?

Thanks man!

 

[racerone]

??---The bulb is nothing but a manual fuel pump.-----Used on outboards to save the starter motor from having to fill the carburetors.----Once running the bulb does nothing and does not need to stay hard at all.

 

[DavidMoore]

The pins will be in the kit.


Yep the anti siphon valve is normally on the top of the tank, it's there so if you have a fuel line failure you don't siphon out all the fuel your tank. Your fuel pump has to work to open it and let fuel through, so if they are too small, spring too heavy, blocked with crud etc they can cause running problems.

 

[gydatree]

CHECK VALVES IN FUEL PUMP! The gaskets that were missing in the fuel pump were the check valves. Without them fuel can flow backwards and lose pressure in the line. Must have the rubber and plastic ones together. Either way, I repaired a bunch of other stuff trying to find the problem, making it run like a top all day once I repaired the fuel pump. Sometimes it can be tough to keep going at idle and real low speeds, but it seems to be getting better the more we run it.

Thanks again guys!

Fair Winds and Following Seas!

 

[gydatree]

Allright guys, its amateur move Saturday. The oil reservoir float went bad a while back so we disengaged the alarm. Went back out tonight and it ran out of oil and seized up. No smoke or anything crazy, it started knocking and slowing down so we turned it off, put oil in and tried to restart with it seized. Before we scrap it, Im gonna go try and un seize it. From what Ive read so far, it seems you can tilt the motor horizontal and inject lubricant into the spark plug holes, let it sit for a day or so then try and move the shaft, possibly by poking something through the spark plug holes. Any suggestions would be greatly appreciated guys!

 

[ondarvr]

It makes no difference if you can get it to move...it's done.

 

[gydatree]

Is that because of the type of seizure we had or just that its seized period?

 

[racerone]

Remove the exhaust cover ( about 20 bolts ) and inspect pistons and rings.

 

[ondarvr]

Once seized there's damage done to the piston(s), rings and cylinders walls, maybe other parts are damaged too. While you may be able to get it to run again, it won't run well, and maybe not for long. If it it's actually seized and won't move, then the chances of it even starting again is slim. If only one cylinder seized, the others may carry it along for the ride, but it won't run well.

 

[gydatree]

Roger that. It looks like the gasket kits to rebuild the powerhead are pretty pricey, assuming thats what one would need to repair at least one of the cylinders, as well as tons of sweaty and nasty man hours. Would my best route be to try and get a couple hundred bucks for this one as a core or something and get a reman'd one for maybe around $1000? Or would it not be all that difficult to pull it apart and take it to a machine shop etc and put it back together? Or should I just give up boating overall?

 

[gydatree]

No Title

Finally removed the exhaust cover. Definitely only the middle cylinder is damaged. As seen in the pics, I pulled a fair amount of debris out, and there is a small piece stuck to the front of the piston keeping it from going all the way forward. Also, there is a small crack in the backside of the piston. Other than that, all 3 pistons look good and move freely, and the top and bottom are still clean and oiled.

My question is, if running it oit of oil were the issue, would the middle one be the first to go? Could there have been another cause?

 

[racerone]

I am not surprized to see that damage after running out of oil.---Motor needs to come apart to see what can be done.-----Take it apart for estimates.------Not many shops can fix that for less than $2000 or so.