1986 Ski Nautique engine troubles (misses under a load)

[Todd_86Nautique]

I have 1986 Ski Nautique 2001 with a Ford 351 engine. The engine misses badly when under a load (runs great when sitting in the driveway). It had the same problem last year and the following was done to try and fix it:

1) Took out points and put Pertronics HEI unit in
2) Replaced spark plugs
3) Replaced plug wires
4) Replaced distributor cap
5) Replaced ignition coil with one having an internal resister and bypassed the ballast resister.
6) Checked, cleaned, and put back in the Fuel/Water separator
7) Had carburetor rebuilt
8) Replaced distributor (which put it back to points).

After replacing the distributor the problem was fixed for about 10 engine hours, then it slowly began to miss again... and got worse and worse. I thought the fix was due to the new mechanical advance in the new distributor.... but not certain.

Last year, the engine would not rev up past about 3200 rpms. This year it will rev up to whatever, but misses and putters the whole time, when under a load.

Both the old and new distributors are Prestolite. As I said, on the old distributor I changed out the points to an HEI system and then back to the points trying to find the problem. The new distributor had to be points because the HEI adapter didn't fit with the new rotor and I had the same problem with all the different set ups.

On Monday night I ran the boat in the driveway. It was really tough to start but when I got it running I put the timing light on it, revved the engine and looked for it to cut out (timing light not flash when it should). It never did, and the engine sounded great! I started it up several times and checked all the cylinders with the timing light, but didn't see anything wrong and it ran nice... except that it was tough to start, until I disconnected the tachometer, then it fired up easy every time. (Is that just a coincidence or is there a reason that might have an effect?) So it didn't make a whole lot of sense to me, but thought maybe that had fixed it.

So, my buddy and I took the boat out to the lake Wednesday night for some more
diagnostics. We put the boat in the water and the first time we tried to take off (thus the engine being loaded by the prop in the water) the engine cut out and sputtered as it climbed up the rpms. (We were discouraged even though we figured beforehand it was probably not fixed) Next we put the timing light on and watched it as we took off. We did this for each cylinder and found that cylinders 1 and 2 never cut out, but cylinders 3-8 sporadically did cut out. As the engine would sputter we could see the steady flashing of the timing light miss a flash one time then miss 2 or 3 in a row others (this is our assumption since the 'cut out' appeared stronger sometimes then others). It was easy to see cylinders 3-8 cut out, and we tested cylinders 1 and 2 a lot but never saw them cut out. The firing order is 1-3-7-2-6-5-4-8 so the good cylinders are not next to each other on the distributor... thus I’m thinking the problem is not associated with the distributor... maybe...???

Any ideas?

Other notes: The HEI unit is Pertronics, but not currently utilized in the engine due to it not fitting the new distributor rotor (will put it back on ASAP, but have to manufacture an adapter to make it fit)... and again, I saw the same problem with the old distributor too with and without the HEI unit.

Thanks in advance… this problem has been plaguing me for over a year and I’m really frustrated!

[hdultra]

RE: 1986 Ski Nautique engine troubles (misses under a load)

Im sure with all you have done you have allready checked this. But when you pull the cap off is their moisture in the cap. If so that will cause some of the problems listed above. If this is the case there is a vent screen on the distributer that gets clogged up with belt dust. Clean the screen and try that. Sorry not that much help.
Good luck

[TRDon]

RE: 1986 Ski Nautique engine troubles (misses under a load)

Had the identical problem in my boat and I put the timing at 12-13 degrees at 650 idle and it took care of it. Sounds dumb but it worked for me, what is your timing at?

[Nautique2001]

RE: 1986 Ski Nautique engine troubles (misses under a load)

I had the same issues with my '86 Nautique. Correct Craft did a leak down or compression test and found that two of my cylinders had lost about 80% compression. It ran worse under load. The dipstick kept blowing out too. You may want to have a compression test done. Good luck.

[Nautique2001]

RE: 1986 Ski Nautique engine troubles (misses under a load)

Also, BTW, the Pertronics EI kit is well known for having high-end issues. I had put a Pertronics kit in mine and it would skip like crazy around 3,400 RPM. It ran great under 3,400 RPM's. I can tell you that two of my friends also had Pertronics kits and the symptoms were identical. I had a Prestolite kit installed and the high speed skipping went away. If you go on www.correctcraftfan.com there are threads about this problem. There's a spacing issue with the module causing the timing to get thrown off. It looks like you went back to the points, which would have corrected this issue.

[SPBFAN]

RE: 1986 Ski Nautique engine troubles (misses under a load)

I have extensive mechanical back ground and I ran in to this issue with a TIGE owner that has a PCM 6.0L 2004 model. They were replacing everything on the engine except the ECM. I had him check his gas. Turned out on his first trip to the lake his boat ran fine and he stopped to fill it up after that . He took it out another day after filling up from his first trip for the year and his boat started acting just like you are describing.

He drained his fuel tank bought new fuel and it worked fine runs like it is brand new. All the misfiring and popping went away. It is possible you have the same problem and may need to pump your gas tank and get new fuel in the boat.

He did tell me that it took about 20 minutes of running with the new fuel and it all of a sudden stood up and took off once all the old fuel and crap pushed through the system.

One other thing. Be sure to buy the mid grade gas. The high grade fuels do not sell and their is a lot of times refineries are taking high grade fuel back from the service station because it does not sell before it starts to loose all of its properties. You can buy bad gas from the gas station if you buy high grade gas. It happens more than you know. They just keep that under a silence order so know one finds out. This is becoming a bigger and bigger problem now because of the fuel prices.

[TRBenj]

Re: 1986 Ski Nautique engine troubles (misses under a load)

it was tough to start, until I disconnected the tachometer, then it fired up easy every time. (Is that just a coincidence or is there a reason that might have an effect?) So it didn't make a whole lot of sense to me, but thought maybe that had fixed it.

The firing order is 1-3-7-2-6-5-4-8

Ive heard of a bad tach backfeeding to the ignition system and causing strange symptoms. Disconnect it for further troubleshooting (gray wire on - side of coil).

Is your engine original? Youre using an automotive (LH) firing order, which is backwards if you have the original RH engine in the boat. The correct firing order is 18456273. Verify which prop you have on the boat- if you have a RH prop (spins clockwise when viewed from the rear), then you have the original RH engine. You'll get better technical info on CCFan, by the way.

[Todd_86Nautique]

Thanks guys!

I'm going to try some of these suggestions tomorrow at the lake.

also, i've already wired a wire straight from the battery to the positive side of the coil with an in-line on/off switch. I was thinking this would check all the existing wiring from the battery to engine by bypassing it. (Does that make sense... can i do that?)

I compression tested all the cylinders last summer right before i replaced the distributor and they were good, can't remember the numbers right now but they were all within about 15% of each other... maybe around 100 psi... i can't remember

I'm gonna hold off a bit before i try draining the gas tank since i'm certain i have used probably 5 tanks worth of gas since i started having the problem.
----- Should i run a carb cleaner fluid through it?

maybe this is stupid question, but if i have the firing order backwards... would it even run?

I guess i'll try advancing the timing some... but that seems like it will cause problems with it running smooth at idle. I can see the timing advance when i rev the engine... it probably advances around 20 degrees.

[TRBenj]

maybe this is stupid question, but if i have the firing order backwards... would it even run?

Very possibly- but probably not very smooth. An incorrect firing order will potentially idle *ok*, but wont like it when you put a load to it. Please do check that first before you go screwing with the timing and fuel. It is very easy to tell which firing order you should be using.

[SPBFAN]

maybe this is stupid question, but if i have the firing order backwards... would it even run?

Very possibly- but probably not very smooth. An incorrect firing order will potentially idle *ok*, but wont like it when you put a load to it. Please do check that first before you go screwing with the timing and fuel. It is very easy to tell which firing order you should be using.

I have to agree. If you have the firing order set up incorrect you will have that problem as stated above. Check the firing order very first.

[knowscc]

Check the condition of the riser gaskets. If compromised, they can leak water into the combustion chambers via exhaust valves. It will run great on a hose, lousy under a load.

[Todd_86Nautique]

also, i've already wired a wire straight from the battery to the positive side of the coil with an in-line on/off switch. I was thinking this would check all the existing wiring from the battery to engine by bypassing it. (Does that make sense... can i do that?)

Well, looks like the mysterious problem is bad wiring somewhere between the battery and coil. I hooked up my bypass and she ran great! Hooked back up the original wiring and it cut out like usual!

I am extremely excited!!!

Thanks to everyone for throwing in their ideas. The only good thing from all this is that i learned quite a bit about engines :-)

I'm planning on re-wiring everything under the dash because it's a complete cluster.... with the stereo and amps and alarm that doesn't work and fat sack pumps.... So that should be a fun project :-)
Also, i'm going to buy the adapter to fit my 1581 Pertronix Ignitor so it will fit my new distributor (or go back to old distributor if i can't get the right adapter).

Any other ideas for improving my engine performance?

Thanks again !