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2006 25hp mercury EFI 4 stroke

L

Lfaber4

New member
Hey all hoping I can get some help here with my engine, I bought a 2007 legend at the end of the season last year with a 25hp Merc on it, took it out for a run and it would top out at about 21mph which I was quite happy with.

Fast forward to this year and the first real fishing trip I spent any time out in it, starts, idles runs perfectly when I first start it and head out from the dock.

I was typically trolling for a few hours at a time and when heading back to the dock for lunch/dinner whatever it wouldn't give me full power, I would be sitting around 13mph and it would sometimes drop down to like 10mph and seem like it was missing fuel then rev back up, but wouldn't speed up to its original top speed.

I checked all spark plugs and they are all in great condition, oil level is good, fuel was fresh... I'm kinda stumped at this point. My dad currently is using the boat up north til sometime today, I had him bring up his fuel hose to see if there was an issue with mine and am waiting to hear back at this point, but if there was no difference I'm not sure where I should be looking to see where my top end range has disappeared off to.
 
You seem to have a fuel issue. Make sure that the fuel system is cleaned out. Tank, lines, filters, including water separation filter. If those are up to par and you still have issues, it could be low pressure pump and or VST (vapor separation tank). Start from there and see what happens.
 
Thanks, that's sort of the line I was thinking of going in terms of diagnosis but I'm no mechanic, if it's fuel related, it should be something I can tackle in my driveway I hope. Local Merc dealer is $115 an hour lol
 
If you don't have codes or beeps going off, then I would stress the above. Check some YouTube videos as there are lots of helpful information.
 
I have already been looking into it lol, and there have been no codes or beeps whatsoever happening so it hasn't indicated something in particular. When I get it back I'll take a look at the vst and low pressure pump, watched a YouTube video and it seems pretty straightforward
 
I managed to get everything apart 2 weekends ago, and while not totally clear it was very clean in the vst, and in general. Took it out for a rip after cleaning everything suggested here and it persisted.


I replaced the gas line and cut open the old one and it was probably half the size it should have been due to what I can assume was old gas or the inner lining of the fuel hose. It was amber and translucent, and it also broke apart into pieces (after I cut the hose apart obviously) it was sort of rubbery.

https://photos.app.goo.gl/G46KhaZL7ujscs2w9

I'm not sure how to post pictures on this forum, so here's a link.. I thinks hahah

Thanks everyone for your suggestions and help!
 
RickM46 said:
So, did the new fuel line solve your problem??
Click to expand...

Yes I guess I left that out haha. Took it out in the river nearby (grand River) and had it out for probably an hour, going WOT most of the time and then trolling down slow intermittently to try and see if I could recreate similar conditions to how it was being used. I was hitting 19-20mph again and planing nicely.

Would I lose a little bit of top end speed with the installation of a hydrofoil? I put one on but only under ideal current conditions will it go much past 20mph
 
Glad to hear you found that it was the fuel line; good to keep the solution in the toolbox for the future. Another fella found on his top end problem, it was the fuel lines and primer bulb.
 
Was your RPM’s running about half and would it do the same thing in Neutral or reverse? I have a thread on a 50hp engine with a similar symptom i’m Trying to fix.
 
X96mnn said:
Was your RPM’s running about half and would it do the same thing in Neutral or reverse? I have a thread on a 50hp engine with a similar symptom i’m Trying to fix.
Click to expand...

I don't have a tach unfortunately, but the rpms would just disappear, it would tail off and go lower than half (by the sound of it) then kinda pop back up and down randomly.
 
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