1999 90 HP Force Issue

[craazy]

I'm pretty sure this is a fuel related issue. Started noticing something fishy a little while back.. if I would idle for a long period of time I would notice a small miss upon take off, other than that the motor would run great. If I idled with the motor trimmed up for a decent amount of time, the rougher the miss would be upon take off. But a perfectly smooth ride other than that. Now the problem seems to have worsened. I don't have to idle nearly as long and the miss is a bit more noticable. But once you get going it's a smooth ride.

I started off checking my fuel flow all the way up to the carbs. My main fuel line is only a year old along with the filter. The fuel pump looked good, no tears on diaphragm or torn gaskets. It appeared my fuel flow to the carbs is fine. I replaced all of my oil lines that run from cylinder to cylinder, they looked a bit rough and noticed a little oil that seemed to be mildly seeping out of two of the lines. Compression is good. 125-130psi on all cylinders. Adequate spark on all cylinders as well. Decided to pull the carbs off and clean them out. Had a little gunk come out of the jets on the middle and bottom carburetors. The floats weren't perfectly level, they were all set about 1/16th of an inch downward (as if the carb were mounted). I made sure they were set exactly the way they were when I put the carbs back together. The needles all seemed to be seating down properly afterwards as well. I pumped the bubble tight after I mounted them back on and nothing was being released. I assumed all should be good to go.

The idling seems to be slightly better now, but still a little bit of a miss during take off after a bit of an idle. The motor will run perfectly fine for a few minutes, then all of the sudden it will lose power for a second or two then pick back up. It will only do this after running approx. 5/8th throttle to WOT for a few minutes. When it loses power, it's not missing at all, just a smooth loss of power. First time it did this, I pulled the cowling off and noticed a milky white liquid all over the middle and bottom carbs. After a while sitting down and not running the motor, it'll just evaporate. I decided to see if it would show up again by only idling for a few minutes. And yes it did. As long as the motor is running for a few minutes, this white milky stuff appears on the bottom two carburetors, while the top one has plain water condensating around it. Yes, sounds like water in my fuel. But I want to learn why it only shows up on my bottom two carbs? Would you think that my motor would run perfectly fine for a few minutes every time before it loses power for a second or so if there was water in my gas? I would think it would cut out immediately as soon as I mash the gas. Maybe I didn't put the carbs back together properly and something is releasing pressure after running for a few minutes? Just wonder if I possibly have more problems than one. What do you think?

I plan on draining my gas tank, cleaning it out, and replacing the vent hose. Other than that, I would like to hear a few suggestions. I have been running ethanol 87 grade fuel as well. I would have to back track a long way to get 100% fuel unfortuantly. Thanks in advance!

 

[Jiggz]

I do not believe that milky stuff is coming off the fuel tank. But more likely a leaky cooling water system coming off the exhaust manifold that is not too severe to stop combustion at high speed (meaning having more fuel entering the cylinders) but enough to cause misfires during idle (less fuel entering the cylinders). The next inspection should be on the spark plugs and it should be done immediately after idling the motor for awhile. Check if there is any water wetting on the face of the plugs. Additionally, I believe you might have some damaged reeds especially on #2 and #3 cylinders. You can also do an inspection through the carb or intake openings.

 

[craazy]

Appreciate the reply. I inspected the reeds while I had the carbs off. They appeared fine. I didn't notice any cracks, but I'm told the only way to truly know if they're bad is through some type of smoke test? I did forget to mention that I have noticed a very small pool of water towards the back of the cowl below the plugs. Not sure if it's coming through my cowling when I come off plane or if it's being spit out of a blown gasket. I will check into that further. I may also take a sample of my fuel and try to find water in it. Another question I have, how does the milky liquid form on the carbs? Seems to be some sort of condensation as the carbs stay cool while the motor is running. No gas or oil is coming out of the carbs anywhere that I can tell. Water is condensating onto the carbs, but how is there fuel/oil mixing with that water to produce the milky look? Sorry for all the questions, but I'm always willing to learn more. Thanks again!

 

[Jiggz]

I am surmising it is probably #1 cylinder that has the water leak and bad reeds. With bad reeds, some fuel oil mix and water will get blown back out of the carbs. Since the milky stuff is only on #2 and #3, this tells me it's most likely coming out of #1 and just running down on the carbs below. One thing for sure, the milky stuff cannot just be plain water otherwise it would just be plain clear water. Condensation from the outside will not produce milky stuff unless of course it gets mixed with fuel oil. So the question is where does the fuel oil leaks from? Unless if it is leaking from the base of the carbs meaning the gaskets are either damaged or not torqued properly.

 

[craazy]

Gives me a lot to keep looking for, thanks for the insight. Very much appreciated. I will report back in a couple days when I get to look around at it.

 

[jerryjerry05]

The carb/float you say the drop is only 1/16th of an inch??
The drop can be as much as 1/2in.
The carb upside down the float should be level .
Try running with the cover off.

 

[craazy]

Sorry, was not very clear on that. With the carbs upside down, all of the floats are about 1/16th of an inch from being perfectly level. You can hardly tell unless you look at them very closely.

 

[craazy]

Have not been able to look around anymore yet. Hopefully tomorrow. I got a chance to talk to a very respectable local mechanic here and told him what all I have done and what the motor was doing. He thought that my bottom two carbs may be lean. He also said that the loss of power sounded like the powerpack was getting hot. Since I stated that it wouldn't lose power until after I run the motor on plane for a couple minutes. I'm thinking I may have possibly created a loose connection somewhere as I unbolted the plate that holds my coil packs, etc. to get to a couple oil lines that I replaced. I just tugged the wires to pull the plate out far enough to get to those oil lines. Didn't actually pull it completely out and disconnect anything. Anyways, I will probably start there and try to find something. Will report back as always. Hopefully with good news. Thanks!

 

[Jiggz]

Great. Hopefully like you said it will all be good stuff to report back.

 

[craazy]

Well everything seemed to check out electrically as I had previosly thought. Did find that my # 2 plug wire was a little loose on the coil pack end. I replaced it with a spare coil pack just for good measure. Made sure all wires were tight and secure. Decided to run to the lake and see if that did anything, or at least learn more about how the problem was occuring. Note: I was by myself this time, no heavy load, etc. Seemed as if I could feel my motors performance better with the boat being lighter. Anyways, idling out from the launch area I noticed the motor would speed up and slow down repeatedly with the same amount of throttle given. Took off to WOT and my gps speed was 3-4 mph slower than it should be. Ran down the lake, turned back up.. Finally came back up on my wake, started bouncing over the waves and the motor started to speed up... finally picked up that 3-4 mph that it was lacking. Kept running for a couple minutes until I came upon some more waves. Motor began to cut in and out on each wave I would bounce over. Turned back around and made a good run back towards the ramp, came up on my wake again and the problem occured once again. Other than that, the motor runs smoothly, sometimes with a 2-4mph loss of speed. Have you or anyone encounted a similar problem before?

 

[craazy]

Either way, looks like nothing is running hot. But still seems like it may be an electrical problem? I would think there's a loose connection somewhere, but have not had any luck looking for one so far.