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Help! Mind boggled

Ciera2450

New member
I have a Penta 5.7osi-af Fuel injected engine. Here is my issue. When the boat has been parked in the driveway for a couple weeks, I take it out and leaving the launch, I wants to bog done and comes down off plane. So I idle back down and try again, well now it gets on plane but the rpms fluctuate 200-400 rpms for about another 5-10 min. After this its runs flawless all day. So I am anchored out over night and when I take off the next morning after everything cooled off and cold and no issues at all. Problem only happens after boat sits parked in driveway for awhile. I have changed the following sensors... IAC, MAP, TPS ad fuel filers. Idles and revs up fine in the driveway also every time. Any suggestions?
 
how old is the boat?

when parked in the driveway, how is the boat inclined?

I'd be inclined to get a fuel pressure gauge and watch it when you expect your issue to occur.
 
Boat is on level ground in driveway. goes out on the water at least once a month. I have tested the pressures idling in the driveway but not on the water. Its almost like "something" sticks after sitting for a couple weeks then frees up
 
Has to be something with the amount of time it sits between trips. Voltage issue? Have you looked into the batteries? Low voltage can cause some pretty strange issues at times. Maybe once they have been juiced up enough by the alternator, they are good to go for the rest of your trip? But then when they sit for 2 weeks they get drawn down again. I'd check for a parasitic draw, and also have them load tested. Also check your cable connections if you have not done any of this already.
 
Has to be something with the amount of time it sits between trips. Voltage issue? Have you looked into the batteries? Low voltage can cause some pretty strange issues at times. Maybe once they have been juiced up enough by the alternator, they are good to go for the rest of your trip? But then when they sit for 2 weeks they get drawn down again. I'd check for a parasitic draw, and also have them load tested. Also check your cable connections if you have not done any of this already.

This is some good advice! I would just add don't forget about ground wires. I've seen grounds corrode inside the insulation and wire looked fine, give it a little tug and breaks off!
 
i was thinking something gets 'stirred up' every couple of weeks.

how old is the boat?

5.7OSi-AF shows as 2001-2002 model years. Probably could have squeaked into a early 2003 model year boat also I suppose.


"Stirred up". Hmmm...Fuel and water? Maybe change the fuel filter/separator? Add some stabilizer to the tank?

EDIT: I see he has changed fuel filter, but I have seen where this might need to be done 2-3 times to get all the water out.
 
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EDIT: I see he has changed fuel filter, but I have seen where this might need to be done 2-3 times to get all the water out.

I've had good success just dumping the fuel filter in a glass jar ( for later examination for water) and then just reinstalling ( and re-oiling the gasket) the filter. If you have a mechanical fuel pump, fill the filter with fresh fuel before reinstalling. After the filter dump does not show any new water ( by looking in the glass jar after about 20 mins) , THEN I replace it with a new one. The fuel water barrier inside the fuel filter is a gas but not water permeable membrane and has a relatively long life. If the fuel dumped from the filter is dirty, then I'd replace the filter immediately the first time.

I had one experience where I had so much water in the tank ( don't ask!!!) that I ended up pulling the fuel sender and pumping it out with a small hand pump.
 
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Thanks guys, I will check out the wiring. It is all on a master disconnect switch. I have dumped stabilizer into the gas as well as new gas. Engine only has 40 hours on.
 
Thanks guys, I will check out the wiring. It is all on a master disconnect switch. I have dumped stabilizer into the gas as well as new gas. Engine only has 40 hours on.

40 hours on a rebuild or 40 on the original engine since new? That's super low hours for what I'm assuming is a 2001-2003 boat. Either way, nothing worse for a boat than sitting. Take it out and run the hell out of it. Get some hours on the clock and the problem may go away. Did you pull any spark plugs and read them for rich or lean conditions?
 
40hrs on a rebuild, been running this way for the full 40 hours, runs awesome after everything has warmed up an been run hard. then it sits for a few weeks and back to the same problem
 
40hrs on a rebuild, been running this way for the full 40 hours, runs awesome after everything has warmed up an been run hard. then it sits for a few weeks and back to the same problem

So I guess the rebuild may open up a different set of questions.

What caused the rebuild to be needed? Did it exhibit any signs of this or similar signs before the rebuild? How long was the engine out for? Was the boat stored outside during the rebuild? Any chance it got rain water in the fuel system through an open line or hose?

Were all wires labeled when removed and double checked that all put back clean and tight in all proper locations?

How warm are you letting the engine get before you take off on the first run where you get the stumbling? Is it getting up to normal operating temp first? Or is it still pretty cold? Any chance the thermostat is sticking? Maybe the intake manifold isn't sealed or torqued well but gets better once warmed up. Could recheck that torque spec. Just throwing stuff at the wall now.
 
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