1993 Yamaha Pro-60 help!!

[rodbuilder]

Hi all. I have a 1993 Yamaha Pro-60 thats acting up. The other day, right after leaving the dock, I opened the throttle and just before the boat reached plane, I lost a cylinder. The motor kept running but only on 2 cylinders. I threw it into neutral and kept the throttle at approx. 50% just to keep it running. After about 30 seconds, the 3rd cylinder started to fire again and the engine ran/idled fine. Again, I opened the throttle and just as before, right before plane, the cylinder (not sure which one) died again. I then shut the motor off and changed the plugs (glad I remembered to buy some!). I fired the motor back up and it ran flawlessly the rest of the evening. Well, that was last week. Last night, I am out in the middle of Cass, and it happened again!! I only had about 2-3 hours on the new plugs. I didn't have spare plugs with this time so I kept the motor running on 2 cylinders but held it at WOT in neutral. After about 30-45 seconds, the 3rd cylinder began firing so I threw it in gear and hauled a$$ for the landing. The motor ran great all the way back (2 miles). I have also noted that since I got the engine (about a month ago), everytime I open the throttle to launch, the thing will cough at around 3500 RPM. When I say cough, it feels like 1 hard misfire and then acceleration resumes. Now for my questions:

I cannot believe that the plugs are to blame. I think it is coincidence that the plug change at the first occurrance temporarily fixed the problem. With that said, does anyone know of any "known issues" with these Yamaha's? WHile the motor was running on 2 cylinders I wanted to pull the plug wires one at a time to see which cylinder it was but I didn't have any insulated pliers in the boat and didn't feel like getting buzzed so I didn't pull anything. Could it be a coil going bad? I had always thought that once a coil goes bad, it is just dead, not intermittently bad. But I am no expert in this area.

I appreciate any/all info!!

[Surface Tension]

The coil can go all at once or just go weak. Look for loose wires at the coil.
After the engine is warm and its been misfiring for a while you can which cylinder it dead by feeling the plugs.
I'm not so sure your coil is the problem. I think you have water in the gas. Let me guess inboard tank? Siphon some gas off and look for water. Raise the tongue jack up and let the boat sit for a while, all the water will settle to the lowest point in the tank with should be toward the transom. Get your siphon hose in that location and on the bottom.

[united jigsticker]

As soon as the motor bogs on you, stop and shut it off. Pull all 3 plugs out and inspect them visually.

The one that is wet, darker then the others, or has any type of build up (hopefully not) will indicate the cylinder responsible. Look for any difference in one out of the three.

Since it is an intermittant problem and seems to quit once the motor is shut down and fires back up, I would say that pulling coil leads isn't going to get you far very fast in this case unless it wil still run foul at idle.

It could be simply just a faulty coil lead wire with a bad connector in the boot, a coil itself, or a fault in the power pack.

It could also be something in your carb, since you say that it always happens before acceleration. If you can find the responsible cylinder, you can pull the drain plug and that carb and purge some fuel through there and see if that makes a difference. I have had some funny things happen on motors in the past that acted similar to this, and purging the carbs did the trick.

You are correct in your thought that typically when something electrical goes bad, it just goes bad. But that's typical, and not all the time.

On a 93, she's probably do for a tune up and some maintenence anyways.

When you say gun the throttle to launch and it bogs, do you mean when you're loading?

I have a 2002 Yamaha that does the same thing when it's tilted up and loading in shallow water (bogs when given throttle for a second). But it also has a faulty primer bulb, so I don't put much stock into that.

------------------
Good fishing,
UJ
[email protected]

[rodbuilder]

ST/UJ,

Thanks for the input. There is something I forgot to add. Everytime I go to start the motor for the first time when I first get to the lake, it takes forever for fuel to reach the engine. I have to give the primer bulb at least 10-12 squeezes, then keep squeezing it while cranking the engine. Eventially, she'll start firing and run. I have had mariners and johnsons and you hardly ever even had to even pump the bulb to get those started. With that in mind, could I be losing fuel flow intermittently because of a bad primer bulb?

I have wondered about water in the fuel. It only makes sense that condensation could develop in the tank. I'll see if I can siphon anything out tonight. Do they make an addative that I could put in my tank to cure this?

UJ, When I mentioned it bogs, its actually more of a stumble. As I am opening the throttle, just as the boat begins to come down on plane, the engine will mis-fire 1 time. The unique thing is that it always does this, but it always only mis-fires 1 time. Its never as if multiple mis-fires are occurring and the engine is falling all over itself. The acceleration is nice and smooth up until about 3500 RPM, then it'll hick-up once, then resume acceleration like nothing is wrong. I am not sure if this is part of the big problem but thought it was noteworthy for this discussion.

Again, I appreciate all of the input. I just spent $6K on this set up and would really like to see this resolved without dumping more money into it.

[Surface Tension]

After checking for water in the tank, replacing the filter and purging the bowls along with replacing the fuel line and bulb would be my next step as well. Oxygenated gas has ethanol in it. Thats fine small amounts of water but not large amounts. Condensation is one culprit but you can also get water right from the gas pump.
Let us know how this turns out and good luck.

[united jigsticker]

Never fear! That pro-60 is a great engine.

Change the fuel filter. It's a white tube in the middle of the fuel line between where the external hose connects to the motor and where the fuel lines run to the carbs. They are about $3-$4, and I am betting it's due!

Get some iso-water remover and add it to your fuel and top off with fresh gas. ($0.99 for a bottle)

If you know how, purge the bowls of the carbs out. There could be gunk and junk floating around in there.

If the fuel line looks old from the tank to the motor, replace it. I had one that gas sat in for 3 years. There was a bunch of white gunk that ran out of the line when I took the ends off and blew through it. If any of that stuff is in your motor lines, carbs, filter, etc...It really messed up my 1996 Johnson.

I had a 77' Johnson that was missing at one certain speed. All I did was turn each of the carb idler adjustments out 1/8 of a turn and it ran like a kitten.

Good luck.

Most of this sounds alot like a gas/detonation problem like mentioned above.

------------------
Good fishing,
UJ
[email protected]

[rodbuilder]

ST/UJ,

I think I got her figured out. This weekend, it happened again. This time, I thought just for kicks, I check the fuel filter. Well, the filter is mounted in a sediment bowl. There was very little dirt in the bowl...but it was FULL of water. Once I dumped it out and restarted the engine, the thing has been running great. Yesterday it hickupped one time during a launch so it looks like there is still more water running through the lines. I spoke with the local Lund dealer about preventing this. He stated that in order to eliminate future occurrances, I need to start filling the tank with the 92 octane "non-oxygenated" fuel (YIKES $$$). It cost me 80 bucks to fill the truck and the boat with 87 octane...hopefully this won't put me over the $100 mark!!

ANyway, thanks to United Jigsticker and Surface Tension for all the help.

Good luck on the water!

[196thDLR]

Rodbuilder: The problem you explained happened to me starting two years ago. My motor was a 1992 70hp Yamaha tiller. I went through all the same fixes that UJ/ST have suggested to you. The only difference, is , that I always filled my tank with 92 Octane NO gas. I purged the whole fuel system, to include, pulling the floor and pressure checking the fuel tank. Next came the fuel pump and fuel filter. That did not fix the problem. All electrical componets were metered to check for a weak part. this was done when the motor was cold and after running under full power until it started coughing. That was not the problem. I had the head planed and a new head gasket put in. That was not the problem.

As soon as the motor would reach operating temperture, it would **** out. A few minutes later when it cooled down, the motor would run like a top up to about 1500 rpms, and then it would run like that for as long as you needed to get back to your landing. I bought a new water pump and impeller thinking that not enough water was flowing through the jacket on the motor. That was not the problem.

I fought this motor for the the next ten months, until last July when I finally got the problem fixed. I bought a new 2003 75hp Yamaha 4-stroke. I had lost total confidence in the '92 Yamaha, and since fishing time is precious, I traded it off. I never did get the problem fixed. I hope you have much better luck than I did.

DLR