Hey guys, I'm having an issue with the motor running at idle, and also just trolling in gear. If I do this for any length of time, the motor runs very ruff, and it isn't running on all cylinders, but when I give it more throttle to get the boat up on plane, it spits and sputters, and even backfires sometimes, but once on plane, it runs perfectly fine. It almost sounds like the motor is "bogging down" like loosing ignition on certain cylinders, and they as I give it more throttle, they pick back up again. I can back off plane slowly and go back onto plane very slowly, trying to get the motor to stumble and it won't, but of course after I idle for a while, it will spit and sputter when trying to get on plane. I'm fairly certain it has to be electrical. So far I've replaced the fuel filter, water fuel separator, trying to see and eliminate water in the fuel possibilities. I brought it to a shop, so far they replaced the distributor cap, and put new spark plugs. That asked me to run the boat yesterday, and it still had the same symptoms. Could it be possible that the fuel pump is going? It doesn't make sense to me though because you would think the boat wouldn't run correctly at all. Could it be the ECM? But even with that you would think it would run right at all if the timing was off. I believe they ran a scan on the ECM, and they said it reported no faults. Any ideas guys? Btw, the boat is a 2001 fountain with hp500efi

I ran the boat tonight to put it on the trailer. It is definatly an over fuel condition. The motor is being dround with too much gas at idle. I could smell raw fuel and of course the engine was stumbling terribly even at idle. With it running, you could sometimes hear the engine trying to correct itself, sounding as if it was trying to suck more air to compinsate. When it did this, you could hear the other cylinders pick back up and it would idle just fine for about 10 seconds, and then again loose the cylinders and dround out with gas. Is there a sensor possibly in the fuel pump that could be going bad?

I had the same thing on my HP500EFI. It was a bad pressure regulator in the cool fuel box. It is supposed to run 40 PSI and mine was running 60 PSI. Exact same symptoms, plus REALLY poor fuel mileage.

Ted g, thanks for the info. May I ask, about how many hours did you have on the boat when the regulator went bad? And what do you think caused it? The reason I ask is because I had the motor pulled to fix a front seal oil leak, and when I got the boat back, the first time I ran the boat, the main water hose above the cool fuel system wasn't tightened properly with a hose clamp, and it worked its way off of the fitting, then was sawn in half by the serpentine belt, spraying water all over the alternator and cool fuel system. My haul has about 325 hours on it.

Check all your wires on the coil and distributor. I had a bad connector that connects to the coil and mine ran exactly like you are explaining. Crank the boat on the hose or in the water then start wiggling the wire that connect to the control module on the back of the distributor there is one connector that has 4 wires and one that has 2 wires. Then check the connectors on top of the coil there are 2 each 2 wire connectors one gray and one black. If it stumbles while you are moving them that could be your problem. The black connector on mine was bad and the weather tight washer was missing off the control module plug.

check your fuel psi at the rail will tell you if regulator working,should be around 30 at idle 40 with the vacuum hose removed if everything else checks out fine you may have a leaking injector,we clean and flow check injectors and see a lot of bad ones in the 500 motors,give me a call if we can help 410-956-5381 Dave

Thanks guys for all the responses. I will be working on the boat after work and will check on those places in particular. I'm leaning towards the oil cool regulator since the shop I brought it to said they changed the distributed cap and checked all the wiring but I will double check since they obviously are not very competant. I also do run injector cleaner so I'm fairly sure they are clean. Also, when I bought the boat last year, the injectors were tested ok and I received that paper work upon purchase and ive probably only put around 12 hrs on the motor so far this summer and I almost always run stabil ethanol treatment too. Thanks again guys.

ok guys, tonight i checked the air hoses from the manifold to the fuel pressure regulator. the hose itself seemed ok, with no holes or tears in it, but where the hose went onto the fitting on the fuel pressure regulator, right on the fuel cooler, the end looked as if it had been torn, so i cut a small amount off and put it back on, by the small chance it wasn't holding vaccum due to this. Put the boat in the water but it ran with the same outcome, being drowned out. Next I plan on checking the fuel pressure. I know a couple of you guys have mentioned to do this there is a fitting/ schratter valve on one of the fuel rails. I looked around but wasn't able to locate it. Maybe it is right infront of me and I'm half blind.

Could someone point me in the right direction where to locate the valve exactly? tomorrow I'm going to buy a fuel pressure gauge and hopefully test it.

Check your PMs

Thanks again