www.iFourWinns.com

I got the fuel pump off,I see the screen at the bottom,,I can see some stuff in there,,Not sure how badly its clogged. But I cant see light from one end to the other and im also trying to blow through there and it is completely sealed and no air is coming out the screen side. Now it may have the pump in the way and thats just the way it is or its extremely clogged?

Also can you remove this screen? I'll scrap some of the paint away but looks like it may be kinda crimped on and not removable?

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1999 Four Winns 245 Sundowner

The screen is not removable. Best is to replace the assy or have it refurbished, I got my assy from here https://mancavemechanic.com/

Also remove your fuel pressure regulator on the fuel rail for the same paint chips.

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2008 H200 Frenzy Edition 5.0 GXi

1993 Horizon 190 5.0 EFI (Sold)

When all esle fails, go back to some basics. Which should include an engine compression cehck. I had exactly the same issues on on my 99 VP 5.7 GSI. Played the parts chasing game for a while, then did a compression check. Turned out I had a cracked head on one bank and a burnt valve on the other. Both head were replaced with reconditioned ones and it now runs the way it was designed.

Im thinking your right on the compression check.Took it for a ride today and still no better after checking both high and low pumps. Both pumps looked pretty clean. Changed out the Map sensor " code is still gone" fuel pressure still good, new wires..plugs,rotor and cap last season,fresh gas and separators changed. All hoses connected,Im at a loss. Compression check is next!

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1999 Four Winns 245 Sundowner

Replace the distributor cap.
They can have a crack inside that prevents power from getting to one or more plugs.
I had a new one after about 6 months go bad one time.
I keep a spare on the boat now.

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The Dance II
2007 278 Vista
6.2L Mercruiser

Sorry to hear it's not been fixed, i went around the houses for a long time with my 4.3Gi engine with the same, primitive TBI Fuel Injection - and eventually after a head gasket fix and new manifolds ripped the whole lot out and re-engined it. I hope you can get yours sorted without continual issues.
It's very difficult to diagnose over the internet without the engine in front of you.
If you need that TBI Manual, let me know.

Good luck

Phil

As I said, I chased this problem for several weeks with lots of research and replacement of lot of parts that could have been an issue such as the fuel pumps. My idle was particularly troublesome and was the cause of much consternation and angt while trying to dock at or load at busy ramps where there was a wait. I also had the “bog” down and could not reach above 2500 RPM at WOT. I finally gave up and had the Marina folks take a look. Their initial thoughts were the TBI injectors but the compression test revealed the real culprit. Once those head were changed out and the engine reassembled with cleaned injectors, it runs like a champ whether at idle or WOT.

Well I gave it a compression test and all 8 cylinders looked good. The lowest was 135psi and the highest was 145 and the rest was all in between that. So I assume I can eliminate some internal wear or blown gaskets valves etc.?
I'll check for cracks in the cap...But somebody told me I should change out my pick up module " not sure of exact name" I thought they work or they dont..Could it be possible that that part is causing power loss?

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1999 Four Winns 245 Sundowner

You won't be able to see the crack. Mine was internal to 2 of the cylinder leads.
I found the problem by way of intermittent fire on a couple of cylinders using a timing light.
Once it got warmed up, they stopped firing all together.

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The Dance II
2007 278 Vista
6.2L Mercruiser

Well I tested everything I possibly could,and still no change.
Only thing I did not check was if the flapper valve in the Y pipe was stuck or broken. From what I hear they dont away with these flappers in 99' and my engine/boat is a 99' so im not even sure if I have them. I looked at a assembly diagram and from the picture it looks like there is a bolt that goes through the Y pipe and has a nut on either side and the flapper rides on that bolt inside the pipe.
So im assuming that if I did have flappers,I would be able to see the nuts on the outside of the pipe? Can anyone confirm this?

It is way back there and very cramped,but I felt all around just below the boot that goes on top of the Y pipe and I didnt feel any bolts,also stuck my phone down and around there for pics and seen nothing.

I did find a mechanic shop on the river where im docked and dropped the boat off so they can test it out and look at it,So I'll be sure to post when I hear back from him with hopefully fixed boat. But if you have experience with these flappers,,let me know!

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1999 Four Winns 245 Sundowner