Pontoon Boat & Deck Boat Forum

Well after having a motor that ran perfectly for the first month plus of use, I'm now seeing some problems that I need help with.

The last two days that we've taken the boat out I've had a problem with a rough running engine until it warms up.
If I try to accelerate the engine sounds as if it's missing.....sputtering, bogging down and surging and it also idles a little rough as well.

Now I've found that I can just let it sputter around for a couple of minutes and then I can advance it to about 3/4 throttle and it will eventually smooth out with only a little bit of sputtering. Then, after about 5 minutes or so of running at 3/4 throttle I can go WOT and the engine runs perfectly. The idle smooths out, I can go quickly from idle to WOT and it basically runs perfectly throughout the entire range.

Now we have had some cool nights here, (in the upper 50's), and I'm running 25W40 oil in the crankcase. Having said that we've been warming up into the low 80's during the day and this is a problem that has happened first thing in the morning and also later in the afternoon.

Any idea what could cause this?
From what I've searched it sounds as if most people have a problem with a motor cutting out and sputtering AFTER it warms up. My problem is the exact opposite.

Any advice is appreciated.

Dave

Update:

Today we went back to the boat with a couple of different things I wanted to try. First of all I found the engine ground point and cleaned up all of the connections. Nothing looked to be terribly corroded but the surfaces of the terminals were not shiny. Like I said I cleaned them all up and tightened everything down.

I'd also wondered about moisture causing my problems. When my motor latch screwed up the cowling seal got pushed up into the cowling, (yeah, I did that trying to fish for the latch). Nothing appeared to be overly wet inside the engine compartment but I still sprayed some Gibbs penetrant over the plug wires just to make sure any moisture was repelled. Oh and if you've never tried Gibbs it is probably the best multi purpose spray known to man. Look it up, online.

One other thing that I did was to leave the gas cap a little bit loose.....not flopping loose but not cranked down tight. I have one of the newer cans that will swell up like a balloon if you leave it sealed in the hot sun so I tightened the cap until it was tight but did not tighten it until it "clicked". I always loosen the cap when leaving the boat so that the tank does not swell. I guess I need to just remove the check ball in the cap and call it good. I'm sure that the great fraud Al Gore would understand my reason for doing so.

Anyway, I don't know what worked but we took the boat for a test run and it performed flawlessly. When I hit the no wake buoys and went to WOT the boat jumped out better than it has since we've owned it. There was a couple of times that it sputtered a little bit but after just a minute or two that went away. I could drop the motor to an idle and punch to WOT and it never hesitated.

One other thing I thought I would mention.....

As I said previously we've been having some cool nights. Last night we only dropped into the low 70's and this afternoon it was in the low 90's instead of the low to mid 80's like we've been seeing.
I still would have a hard time believing that this motor is so cold blooded that it can't operate in temperatures ranging from the 60's to the 80's.

So, if anything changes I will give another update. Hopefully you don't hear from me again, concerning this problem.

sorry, double post

Could be that you had some iffy fuel. The temp should not have mattered. Are you using vented portable tanks? If so make sure the vent is open when you are using the motor.

Those motors have a pretty complicated carburetor system with each cylinder having its own adjustment. I think they call it link and sync. If one is off it can cause the problems you are having as you could be starving or flooding one cylinder.

mpilot wrote:Those motors have a pretty complicated carburetor system with each cylinder having its own adjustment. I think they call it link and sync. If one is off it can cause the problems you are having as you could be starving or flooding one cylinder.

Yeah, I don't think I'll be tackling anything with this type of carb system, anytime soon. Just looking at it makes my head spin.

I'm hoping that I've nailed the problem down to moisture in the ignition system. I had a faulty seal on my cowling and I've had success with spraying my wires with Gibbs, twice. Each time I sprayed the wires down the engine has ran flawlessly. But, with the cowling seal still bad the problem would return because of re-introducing moisture during the test drive, (at least that's what I'm hoping).

Today we pulled the cowling and made a repair on the seal. It is now sealing like it's supposed to. The motor was left in the sun, uncovered for a couple of hours so hopefully that dried everything out. If the problem reappears during tonight's test drive I'm going to spray it again and hope that the repaired cowling seal will do the trick.

The only other thing that might be happening is that the plug wires are extremely bad and the Gibbs spray is "making" continuity on the wires. Having said that, the wires look like they are in good shape so I doubt that is the problem.

If repairing the cowling seal works I'll give an update so that this thread will hopefully help someone in the future.

jrolin1 wrote:Could be that you had some iffy fuel. The temp should not have mattered. Are you using vented portable tanks? If so make sure the vent is open when you are using the motor.

I thought about the fuel problem as well....

I'm using one of the newer portable tanks that do not vent into the atmosphere, (thanks Obama!). Because of that I have to leave the gas cap cracked or the tank will blow up like a balloon in the hot sun.
I was afraid that the fuel had drawn moisture because of that but I don't think that bad fuel would run good one day and bad the next.
As I said above I'm thinking the culprit might be moisture but only time will tell.
I do appreciate your response and suggestion and I'm not ready to discount the fact that you might be right.

Also, I did try running the motor with the gas cap on very loosely with no success. The only thing that has helped is spraying the plug wires with a moisture displacement spray.

You may want to try replacing the fuel line. An inexpensive way to eliminate that potential issue. If you have another fuel tank I would give that a shot also in case the pickup had an issue.

Likesspace wrote:

mpilot wrote:Those motors have a pretty complicated carburetor system with each cylinder having its own adjustment. I think they call it link and sync. If one is off it can cause the problems you are having as you could be starving or flooding one cylinder.

Yeah, I don't think I'll be tackling anything with this type of carb system, anytime soon. Just looking at it makes my head spin.

I'm hoping that I've nailed the problem down to moisture in the ignition system. I had a faulty seal on my cowling and I've had success with spraying my wires with Gibbs, twice. Each time I sprayed the wires down the engine has ran flawlessly. But, with the cowling seal still bad the problem would return because of re-introducing moisture during the test drive, (at least that's what I'm hoping).

Today we pulled the cowling and made a repair on the seal. It is now sealing like it's supposed to. The motor was left in the sun, uncovered for a couple of hours so hopefully that dried everything out. If the problem reappears during tonight's test drive I'm going to spray it again and hope that the repaired cowling seal will do the trick.

The only other thing that might be happening is that the plug wires are extremely bad and the Gibbs spray is "making" continuity on the wires. Having said that, the wires look like they are in good shape so I doubt that is the problem.

If repairing the cowling seal works I'll give an update so that this thread will hopefully help someone in the future.

If you download the service manual it's not bad actually. You basicallyou get them all set the same and adjust the idle and wide open from two spots. Don't try to do it without the guide like I did. Spent a week trying to get it right then got the instructions and it took me an hour to get it dialed in.

Likesspace wrote: I'm using one of the newer portable tanks that do not vent into the atmosphere, (thanks Obama!). .

??? EPA regs were updated in 2007 with a phase in date of 2009.