Engine bogging, need new ideas

[SpartanSki]

I've posted before about the engine troubles I've been having with my Malibu. 335 monsoon in a sportster lx, occasionally it will bog and lose power, giving it more power just causes it to backfire. Pull to neutral, idles smooth, pull up again and it runs fine, most likely will do it again though. It doesn't do it cold, only after running for about 30 minutes or more.

 

I started with the easy stuff, cleaned out the inlet screen on the fuel pump (external pump), changed the fuel filter. Then pulled the tank and cleaned it out, replaced the anti-siphon value, new fuel lines. Still doing it so I replaced the fuel pressure regulator, still doing it.

 

Put a fuel pressure gauge on it and it reads 5psi at prime, 35 at idle, 38 at ski speeds and just over 40 above 40 mph. when it bogs the needle is shaking but that could be because of the vibration of the engine while bogging, but there is no noticeable change in fuel pressure when it loses power.

 

Do I just suck it up and put a new fuel pump on it (it's about 300 bucks for my model), or do I start looking else where? Ignition maybe? I'm pretty much out of ideas so any help would be appreciated. Thanks guys.

[rayn]

Do you have the ability to read the codes from the computer. I had a similar issue a number of years ago and it turned out to be the computer itself. I fried it when I connected the battery when the key was in the on position. I was lucky as there are a number of Monsoons around here that helped me by just exchanging parts until like you eliminated basically all possibilities. I also tried the fuel pump route but that didn't fix it either.

[skosney]

I have a couple of thoughts.

 

1. Water in the Fuel - I'm not familiar with your particular boat/engine configuration. Is there a water separator/filter (in addition to a traditional fuel filter)? If so, remove the canister and check for water mixed in with the fuel at the bottom of it. Even if you don't find anything there, I would remove as much fuel as possible from the tank and replace with fresh fuel and a bottle of gas dryer (i.e. "Heat").

 

2. Ignition Coil Condenser - Typically when these start to go bad, they act up once as the warm up. The fact that the problem goes away for an extended period of time after you bring it down to idle leads me back to bad fuel/water, but electrical components can also display sporadic issues.

 

The backfiring leads me to think it is something other than fuel pressure/pumping so I would not replace your pump just yet.

 

My two cents based on past experience over the last 35 years of being around inboards.

[SpartanSki]

Thank you guys. I think I can cross off water and fuel because I pulled the tank drained it and cleaned it, and it dried for about 2 weeks before going back in to the boat completely empty. There is no fuel water separator either.

 

Computer is a good thought, can the codes be read from a regular automotive scan tool?

"2. Ignition Coil Condenser - Typically when these start to go bad, they act up once as the warm up." This is an interesting one and I'm going to look at that next.

 

The problem doesn't go away after it sits at idle. From cold when I first leave the dock I have no issues, but about 30 minutes into running the issue will start. The boat never stalls when you pull to idle and I might have full power to get back on plane but it will act up shortly after that.

[skosney]

Ok then it sounds like a classic case of a failing coil condenser ... Easy and inexpensive repair.

I'm surprised there is not water separator. Might be a good add-on at some point.

 

I hope that solves the issue!!!

[LeonL]

Malibu huh? Just wait til @ilivetoski reads this one. He'll give you a horror story of parts hanging.

[evolski]

Is your monsoon fuel injected - if it is - does it have metal cross overs in front and back of the air intake - if it does, they need to be replaced by the new rubber ones. If this isn't it, I hope you find the solution.

[DmaxJC_ski]

Sounds like a lean backfire caused by a air/vacuum leak.

[LeonL]

Yeah, backfires are most generally caused by a lean condition. I've even heard of an exhaust leak causing the ECM lean out the fuel flow, sniffing the exhaust makes it think it's too rich.

 

[SpartanSki]

@LeonL and @DmaxJC_ski‌ if it helps the diagnosis, it only backfires if you give it more throttle once it starts losing power. It will start bogging and have trouble staying on plane and if you just pull the throttle back it won't backfire. If you try to give it more to stay on plane, then it will backfire. In any case, where do I start looking for possible leaks?

 

@skosney‌, is the coil consdenser just the ignition coil or is there more to it than that? The boat is an 03 so should I do the cap and rotor as well?

 

@evolski‌, yes it's fuel injected, I guess I don't follow. The air intake is on the back passenger side of the engine and is the semi cone shaped K&N.

[evolski]

ok, different intake, there are 2 fuel lines the go from the left to the right side of the engine, one in front the other in back - if these are metal they could be causing the problem.

[LeonL]

As far as exhaust leaks just run the engine, open the cover and smell. Vacuum leaks (I doubt that's the problem) use a propane torch (not lit of course) moving it around the intake area and listen for a change in rpm. Some will scream about safety, but really no problem.

[rayn]

I never bought this, as I just brought it to the dealer eventually and had them check it and replace it. The connector is different than in a car, and the dealers have the cable and PC. My understanding from the guys at skidim that this will read the codes, it was not something i wanted to try since it was such a time synch already. Good luck.

 

http://www.skidim.com/prodinfo.asp?number=RIN94008

 

 

[skosney]

Cap and rotor are probably fine but if they are from 03, you may want to do a complete tune-up of your ignition system including new plug wires. Take a look at the cap/rotor and clean any corrosion at least.

 

While the ignition coil is also a possibility, I would start with the condenser first, which is separate but connected to the coil. Typically it is a small cylinder about and inch long and maybe a half inch in diameter with a single wire that attaches to one of the coil terminals. They are relatively inexpensive and I don't believe there is any difference between marine and automotive (but I could be wrong). Make sure the mounting location is clean to ensure a good ground. If you can, I'd pick up a new coil as well and if the problem persist after replacing the condenser, try the new coil.

[DanE]

@SpartanSki‌ Are you sure it is backfiring?

Unburnt fuel combusting in the exhausts will make a similar moise and is usually caused by malfunctioning ignition.

[DanE]

And by the way, go ahead and replace cap,rotor,spark plugs and wires if you haven't already.

At some point you have to so now's a good time to save you some troubleshooting.

[MillerTime38]

@SpartanSki‌ to check the condenser run the boat until it gets warm and acts up, then take the condenser off dip in water to cool and put back. Try to run, if it is the condenser the boat should work again. If not, move on

[DW]

@Spartanski: As noted the symptom sounds very much as a lean misfire particularly when you give it more throttle opening, it sounds like it is not getting any more fuel. The TPS may be defective (more air but not more fuel). Might be a cracked distributor cap which may be hard to see. The comments on the rubber fuel rail lines is commonly called fuel hammer caused by lack of flex in the fuel rail and lines. Your data implies it is not the pump, but have you checked it for temperature when running well and when acting up? One of the cheap Harbor Freight infrared temp gauges is great for that type of diagnosis.

[SpartanSki]

@DW I don't think it's the TPS because this all starts before I move the throttle. The boat could be holding at 34mph the entire lake and then all of a sudden start losing power and bogging with no change in throttle position. If I then try to give it more throttle to try to stay on plane then it will start backfiring, or what sounds like backfiring to my untrained ears.

 

The temp is an interesting one, are you talking about the temperature of the pump itself?

 

Anyone know where to find a replacement condenser, are the automotive and marine ones interchangeable?

[gregy]

What altitude are you at? Those engines are known to vapor lock especially at higher altitude. Skidim sells a kit to add a pump near the tank. Also my 99 monsoon goes straight to 40 psi when I turn the key on when priming.

[SpartanSki]

@gregy, I'm in michigan, ~1000ft no altitude sickness here... And this engine has run flawlessly for 700 hours living on the exact same lake.

 

The pressures are interesting though because we are on the low end of what indmar shows as normal. But I could watch the pressure gauge rise as I give it more power and if I wanted, drop the hammer and it would shoot up to 40 run fine then halfway down the lake quit without any noticeable drop in fuel pressure.

 

I'm going to pull the cap and rotor, ignition coil and condenser tonight.

[gregy]

@SpartanSki‌ maybe a ground wire bad connection. One of my ski partners had a random problem that 2 dealerships could figure on a 08 ps197 525hrs. We got some monitoring software and noticed the timing was jumping around. Pulled the distributor and teeth were badly worn.

[GregHind]

@spartanski I doubt the fuel pressure is meant to change. Should be fixed at one pressure. This applies with key on engine off even and of course from idle to wot

[E_T]

My guess flux capacitor aka coil

[Winston]

Run engine in darkness see if any arking out on wires or cap area if not when you get it up to temp and problem arrisses again spray carb cleaner along intake mainifold seams to head if it makes a change in rpm you have a intake manifold gasket leak sometimes i have been able to tighten 8 bolts on each side and closed up air leak hope this helps

[Ilivetoski]

Same issue (kinda) with our 04 LXi. Started with huge loss of power, so we took it into the shop. Lets put it like this, we have an entire new ignition system, transmission plates, most of the fuel system was replaced, ECM was replaced 2 times, completely new throttle (incase you cant tell, they were just throwing things on the boat hoping it would work), and many many many more parts that I cant even think of. In the end it cost us near $3,000. After the power issue was fixed, the backfiring started. Listen to me on this. After $1,000 trying to fix this it turned out to be a clogged fuel injector. HAVE HIM CHECK YOUR FUEL INJECTORS. It would have saved us so much time and money as replacing the fuel injector was something like $100. I could go on for an hour about how frustrating the whole thing was for me. My dad was out last year due to a rotator cuff and bone spur surgery. So while it was annoying for him it really cost me ski time (and having to ski on a public lake.... I dont count that as quality ski time) it really hurt me last season and my scores showed it.

[DmaxJC_ski]

Good call @Ilivetoski‌, how I check for vacuum leaks, keep in mind I am a farmer and a hot rod builder, somewhat redneck too, is with the engine comp open run it to the point of bog, spray a bit of ether or WD 40 around the intake runners/throttle body, if you Hear the bog go away or the engine fire properly, you know you have a vacuum leak. That being said you have to be fairly precise to not start a fire... Beings as it starts doing so after its good and warm (expansion) makes me lean towards a vacuum prob.

[acmx]

@SpartanSki , check this out http://www.themalibucrew.com/forums/index.php?/topic/38790-03-xti-monson-335-loosing-power/

[SpartanSki]

Thank @acmx so his sounds similar and the issue was the pickup coil. What's a pickup coil? And a friend said that unless your engine has points which I'm fairly certain a 2003 monsoon EFI doesn't then it won't have a coil condenser, is that true?

[SpartanSki]

ARRRG! Pulled the cap and rotor and they were in terrible shape. The metal contact on the rotor was completely rusted away, with the contacts on the cap covered in corrosion and oxidation. Replaced both thinking this has to be it...no. Replaced the ignition coil...no. So it's on to vacuum tests I guess, that and injectors.