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2007 Mercury 90HP EFI 4-stroke idle issue shuts off

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slowride56

New member
Hello Forum, I have a 90 efi 4 stroke Ser# 1B475763 I bought this motor knowing it had fuel issues. Replaced both pumps and float checked hose and cleaned regulator, flushed out injectors and rail, new filters. engine starts and runs if you give it some throttle, fuel psi is 42-44psi. has good compression and new plugs. Took it to the Lake it runs fine above no wake speed real smooth no issues, but when you throttle down to no wake speed it start to get a little rough and then shuts off like you turned the key off. starts back up but barely idles. I checked the IAC valve and it appeared to not be opening all the way when energized. So i replaced the IAC valve and MAP sensor. Neither helped my situation. Leaning toward injectors anyone have any ideas?
 
johnnygjr said:
Have you checked for trouble codes?
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No I do not have the means to do that and the boat is in the water will be a while till i can get it back out. washoping that someone had a similar issue to mine. I am leaning toward injectors or TPS as there is not much else Left.
 
slowride56 said:
No I do not have the means to do that and the boat is in the water will be a while till i can get it back out. washoping that someone had a similar issue to mine. I am leaning toward injectors or TPS as there is not much else Left.
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Did you ever figure this out? I'm having a similar issue on a 30hp EFI.
 
I also am having this exact issue. Cleaned tank, changed all filters, new fuel ran good for one day then back to doing it again. Kinda dangerous when docking
 
Same problem with my 2007 Mercury 90ELPT 4S! I drained my fuel tank & filled it with non-ethanol. I replaced both of the in-line fuel filters. Engine still cuts off when I shift from “in gear” to neutral. It happens every time. It doesn’t seem to make a difference whether I’m shifting from forward or reverse into neutral. Obviously, this is a problem when trying to dock or put on the trailer. It will restart in neutral & idles fine. It doesn’t cut off when I shift from neutral into gear (F/R). Otherwise, it runs fine at any speed. I would think the idle is too low, if it cut off when shifting from neutral into gear, but my problem is just the opposite! Any thoughts or suggestions? Thank you in advance!!!
 
ChrisSupple said:
Same problem with my 2007 Mercury 90ELPT 4S! I drained my fuel tank & filled it with non-ethanol. I replaced both of the in-line fuel filters. Engine still cuts off when I shift from “in gear” to neutral. It happens every time. It doesn’t seem to make a difference whether I’m shifting from forward or reverse into neutral. Obviously, this is a problem when trying to dock or put on the trailer. It will restart in neutral & idles fine. It doesn’t cut off when I shift from neutral into gear (F/R). Otherwise, it runs fine at any speed. I would think the idle is too low, if it cut off when shifting from neutral into gear, but my problem is just the opposite! Any thoughts or suggestions? Thank you in advance!!!
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That stinks, totally frustrating I know. Mine actually still did it over last summer and this past summer. I talked to mechanic that knows Tohatsu (which is what mine is a rebranded Tohatsu) and he said it's common on my engine, and to just raise the idle 50rpm. I will try that, but haven't yet. Yours sounds more like a throttle position sensor error, or safety switch issue since it does it every time.
 
Thank you for your reply. I got so frustrated with this issue that I paid “JustAnswer.com” for a mechanic to reply. BEWARE if you ever do that. It only costs $1, but when you sign up, you agree to a $39 monthly subscription! Anyway, the mechanic says that it’s 99% probability of the Neutral Safety Switch. It’s a small plunger switch in the bottom of the upper cowling. There’s a cam at the end of the shift cable that activates it. He said that it causes the motor to quickly stumble when shifting from gear into neutral, which unloads propeller force load for a split second, allowing an easy shift to neutral & keeps idle rpm steady. He said to use a small flathead screwdriver & push the plunger in & release when idling in neutral. Engine should stumble for a split second if the switch is working properly! I haven’t tried it yet, but I’ll reply to this as soon as I do. This is the first outboard I’ve ever worked on. My previous boats have all been V-8 I/O’s. Thoughts on this are much appreciated!
 
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