Crappie are hot, my motor is not.

Well, This is the time of year I love the best for chasing crappie. I was doing pretty good using DK’s single pole technique and now my boat motor is failing me. 2007 Optimax has always run great. Now it will run ok for about 15 minutes then dies and won’t stay running....won’t even idle. Let it sit for about 15 minutes and it will start perfect and will run at an idle long enough to get it on the trailer. Fuels good, no trash in the filters or in the fuel pump chambers. It’s sure got me scratching my head.

Maybe the inside of your fuel line has degraded.

Happens all the timeAttachment 387358

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:hesaid

No. I replaced it all a couple of years ago . I’ve also cleaned the fuel pump housing and all screens and filters.

I had a similar issue with my 89 yamaha 150. Went through all the easy fix fuel lines, filter, rebuilt the fuel pump stuff myself. Finally took it to a mechanic. He said it was a piece of something (probably file line) in one of the carbs that would settle and then get sucked into a jet and block the fuel flow while it was running.

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Thanks for the suggestions. I guess I’m going to have to find a good mechanic. Any suggestions?

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Originally Posted by Grumpygramps

Thanks for the suggestions. I guess I’m going to have to find a good mechanic. Any suggestions?

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Glenn Gamble. Outboard Docs I think is the name of the business.

I’ve been out of town a couple of days and just saw this. I’ll sure give them a call. Thanks DK

Try pumping the priming bulb when it begins to stop running. If it picks up and runs ok, it is almost always a hole in the fuel line. Doesn't matter how old it is. I have seen new ones with a hole in them. Cheap check before you take it to a mechanic. Mine would run fine for 10 minutes or so then begin spitting and sputtering until it shut off and it was tough to get it started back up. But if I kept pumping the bulb it would run ok. The hole was causing an air pocket cutting off the gas.

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Originally Posted by Grumpygramps

No. I replaced it all a couple of years ago . I’ve also cleaned the fuel pump housing and all screens and filters.

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Just because you replaced it 2 years ago is no guarantee that it is still good. Some of the fuel lines being sold now are crap and they can go from OK to bad in a heartbeat.

Did you make sure your fuel filler cap is venting properly? If it is not... it will pull a vacuum inside the fuel tank... after just a few minutes which will prevent fuel from moving freely through the fuel line.
Because you said it will usually crank after sitting for 15 minutes: This could mean the fuel tank equalizes some due to the vacuum pulling some air through the fuel cap allowing it to start and run only briefly.
Try loosening the fuel filler cap to allow more than normal air flow and see what happens.

One more thing. It appears that you have not yet run the ultimate definitive test for problems like this - that being the temporary fuel supply. Find a buddy that will loan you a good portable tank with hose, disconnect your fuel fitting at the motor and plug in the portable. If the problem returns, then you know for sure it is in the motor somewhere. If the problem goes away, you know for sure that it is somewhere in your fuel storage/delivery system. Diagnosis by the process of elimination.

When you are having this issue...Are you getting any alarms? I've had mine do similar to that twice. Both times it was the 100amp linked fuse between the alternator and the battery giving juice back. I would get 4 chirps every 2 minutes telling me my oil resovior was low. And I know it was topped off. Them engines will do squirely things when the voltage supplied is low. A simple ohms test between the terminates will rule this out.

My engine is a 2008 75hp Optimax

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My fishing partner just spent nearly 6 months trying to trace down a similar issue of running fine and then not. After several expensive mechanic bills, it was discovered that his low pressure fuel pump was not operating properly. May not be the problem but his is an Optimax and did exactly what you stated. Might be a good check.

I had to change all fuel lines around my engine,,,found most were closed solid from alcohol/ ethanol....

I had the same motor and same problem. I was sure it as fuel, replaced fuel lines and filters emptied gas and started with fresh. Nothing helped. Took t to a shop spent over a $1000. They replaced fuel pumps and it was slightly better but still died after 10-15 minutes. I did a lot of web searching and found my issue.
I don't know if your coils were ever replaced but there was a recall on them and Mercury replaced them for free for original owners.
You can get the number off the coil and do some web surfing it maybe your issue. I sold that boat a few years back but after replacing coils never had another issue. I got 3 off of Ebay for around $100 a piece. Easy to replace yourself.