Intermittent power/performance loss 225 EFI

[Jajbs920]

2006 Opti 200L SN 1B379785 hanger with a mid to late 90's 225 EFI powerhead
2007 Triton 197 Magnum, 4 blade trophy 24P

I've been having issues since I changed my lower unit out. The first time I ran my boat after the LU change, I had 4 people in my boat and it wouldn't do the normal 50 mph at 4500 rpm's and it would barely get over 55 mph turning 5000 to 5100 rpm's. I thought that I had bought a LU with a different gear ratio. During that first outing, it performed as normal right after launching and my holeshot was normal. After fishing for a while, I went to go to another spot and it wouldn't come out of the water. Pedal to the floor and it would just plow through the water and wouldn't get on plane. I stopped, revved it a bit to clear it's throat and tried again and it made it on plane, but wasn't running as smooth and strong as usual. Also, it felt like I was running out of trim and not getting near as much lift as before. Since then I've changed the plugs, cleaned the screen on top of the VST and checked the TPS. Went out today, again with 4 people and it ran great, great holeshot, but still lacked on the top-end and wouldn't do 50 mph at 4500 rpm. I've had 4 people in it before and was able to do 50 at 4500 in the past. Then it started the same issue not getting on plane and running odd...kind of rough, or not as smooth as when we first started. When we finished not catching any fish, I dropped everyone off at the launch and ran it alone. Awesome holeshot, ran 50 at 4500 and ran about 68 mph at 5750-5800. It also wouldn't get up on the pad and that usually happens at 65 mph. When I went to load it and was trying to push it up that last little bit on the trailer, it seemed to have no power, kind of the same issue as when trying to get on plane. Before the plug change and screen cleaning, it would do around 5000 rpm at half throttle and the rest of the throttle seemed to just be wasted pedal and it would even seem to slow down at WOT. It did that today also, but would also run great...doesn't make any sense to me. Any thoughts or suggestions would be greatly appreciated. Thanks!!

[Gamblinman]

Why did you change LU? Did you strike something?

Was the VST screen clogged?

What gap did you adjust spark plugs too? Make double damn sure you have the plug wire seated properly on the spark plug.

[Jajbs920]

I broke the prop shaft in half. Turned out that I had an SEI LU and not an OEM. I got into some shallow water, trimmed the motor up and tried to get through it and it just quit moving...that was it.
The VST screen had some gunk or slime built up around the edges, but wasn't totally blocked off.
I put Champion QL77CC plugs in it with the gap at .035.

It ran like a top up until it didn't. After the first episode of it feeling bogged down and unable to get on plane, it felt different and not near as smooth. It's really strange. With just me in it, it felt good.

[Gamblinman]

Based on having gunk and slime build-up on your VST screen, I advise that you completely clean your fuel injection system. VST needs to come apart and cleaned, fuel injectors cleaned, flow tested, and balanced, and pulse pump rebuilt . If you haven't already, replace all fuel lines from tank to engine including bulb with ethanol resistant lines. With todays fuels, these items are becoming necessary on a more normal maintenance basis. Not cleaning, replacing or rebuilding any of the above items could leave residue that could start the process over again.

[Jajbs920]

Thanks. I'll have to put a plan together to start doing that. I'm also premixing. The oil injection has been removed from this powerhead...sorry I neglected to mention it, I stated in a thread about my LU issues and forgot to re-state it. I bought the boat used in Feb and I'm finding out all kinds of things I didn't know...it's definitely been an enlightening experience. I also just started using quikleen when I put fuel in it before the first run after the LU change. Could this have caused any of these issues? The part that's strange to me is the inconsistentency of it. Thanks for the help. My learning curve is standing straight up and trying to keep up. You guys are all brilliant in my eyes.
PS- To my knowledge it has only had non ethanol fuel in it since the efi powerhead was built and installed ~60 hours. Don't know if that makes a difference or not.