Mercruiser 525 won't start intermittently
 

Hey folks, new to the site and wanted to see if anyone had this problem or can help. Boat starts every morning no problems. Three beep code, scanner shows fuel pressure ckt high. Cracked the water separator line and started. Any idea where to start? Haven't called Nordic yet, couldn't find anything on the web. When the boat starts no problems, just scared to shut it off, bad feeling.

Sounds like vapor lock but have never heard of vapor lock being an issue on 525EFI's. Are you running ethanol fuel?? E10 will cause vapor lock more easily.

Nope, just 91 from the pump. Thought about vapor lock.

Could be the sensor or fuel pressure is high. Don't have a 525 manual but other manuals list 2 beeps per minute with the error

525EFI Owners Manual:
http://download.brunswick-marine.com.../841196060.pdf

525EFI Service Manual Serial # 0M953620 & Above:
http://www.ibs-ny.com/freedom/Engine...e%20Manual.pdf

Id put a fuel pressure gauge on it and see where its at, fuel regulator ?

Doesnt start is vague. Does it crank over at full speed. Does it sound like it tries to fire alittle. Does exhaust smell like unburnt fuel etc.

Keep in mind, some states only sell E10 fuel on land. MO is all E10 fuel on land unless it specifically says non ethanol premium. Learned that the hard way on 100* day.

Mercury spec on octane rating for a stock 525 EFI is 87..........91 might be giving you some issues

Does it not start after a hot soak (raft up)? I'm a little confused at when the problem is happening.

My 700sci's (different induction, of course) would certainly vapor lock, almost every time we were at a raft up for an extended period. But cranking and key cycling to help push the air through the injectors would resolve until the next hot soak.

Ethanol content in fuels aggravate vapor lock due to the lower boiling point of ethanol.

That is a good point.

It cranks at full speed, like normal. Can't really smell gas,it's like it doesn't have spark. Thinking the computer is not letting it start. I thought I was doing good by putting 91 in it.

Still need a bit more info to clearly understand what is happening.
It starts when cold, go it

It doesn't start some times when warm.... Only after sitting after running and rafting up or other, or maybe just shut it down and 5 minutes later it won't start.

What happens between after the last time is started and this time it will not?

In the slip fires up, drive 10 miles at 4000 rpm up to wot. Get to beach let it cool down in no wake zone open the hatch. Hour later wouldn't start, checked everything cracked the fuel line at separator then it started. Next day fired up same went to the beach a couple hours later it started drove for a few miles stopped jumped in the water, then it wouldn't start got towed back to the beach. Went to go back home and it started. Thinking vapor lock?

Yes, sounds like VL
Can fix it by taking the return line and route it back to the tank (mines fixed this way). Otherwise take a rage and small screw driver or other. Remove cap off schrader valve, place rag over valve and press in on it. Turn key to ON a time or 2 until you get all gas come out


https://cimg9.ibsrv.net/gimg/www.off...51aec41b60.jpg

Yup many complaints of 52%EFI vapor lock issues over the years.
Try this for a search:
https://www.google.com/search?q=525E...hrome&ie=UTF-8

If that doesn't work, go to Google search or etc and type in: 525EFI Vapor Lock
and it will bring up many OSO threads

Awesome thanks I'll check it out.

I only run 87 octane Chevron pump gas in mine, in central TX, 100+ degree days. Ditto on the comment re 91. maybe start by lowering down to the reg unleaded. Merc Racing told me the 525 was built specifically to run on 87, and nothing more (needed).

I'd say if you are cracking the fuel sep filter open and it starts right after that, then its 99% for sure vapor lock.
87 octane non ethanol is the best fuel to run in them, but use whatever octane you have available that is non ethanol.