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 37 EFI GTR Issues 
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Post 37 EFI GTR Issues
So up until this morning I haven't had many issues with my mudmotor. Granted, it's a 2015 model and I only have 53 hours on it. Headed out this morning I noticed it was running full speed and wasn't turning RPMs. Shortly there after I had a sputtering/backfire type of noises consistently coming out of it and it would only creep. I went ahead and serviced it when I got home. New fuel filter, new spark plugs, changed oil, checked lash etc....

Decided to go run it again and it ran like a top until I started idling around my neighborhood. It started sputtering again etc... I've read a lot of threads on the getting air issues. I tightened all my worm gear clamps, my lift pump is pumping gas to the filter, I don't have any quick connects, no water in the gas, etc.... Not real sure where to go from here? Any advice would be greatly appreciated.


Sat Aug 04, 2018 2:31 pm
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Post Re: 37 EFI GTR Issues
Also, is a 2015 model with 53 hours still under warranty?


Sat Aug 04, 2018 2:32 pm
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Post Re: 37 EFI GTR Issues
Sounds like you may have a sensor issue. Will or Maxxis ought to chime in soon and be more accurate as to what to check or do.

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Sat Aug 04, 2018 2:54 pm
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Post Re: 37 EFI GTR Issues


Sat Aug 04, 2018 4:07 pm
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Post Re: 37 EFI GTR Issues
dont know what years were affected by the bad harness, but this is the same issue my buddy had with his when his harness went out. pretty sure its covered under recall or warranty. I would bring it to andy at boat dr and get his advice on it, he can point you in the right direction


Sat Aug 04, 2018 9:21 pm
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Post Re: 37 EFI GTR Issues
Maxxis is a lot closer. Cleveland, tx now, I think.

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Sat Aug 04, 2018 9:50 pm
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Post Re: 37 EFI GTR Issues
Since you have checked the valves it could be a few things. 2015 prob doesn't have the check engine light but you may have a code. Find your purchase receipt. 3 years from the date on it


Sat Aug 04, 2018 11:56 pm
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Post Re: 37 EFI GTR Issues
Yea I remember people talking about the harness issues. I’m hoping it’s something like that and is covered somehow. Figured I would have issues right at the 3 year mark...


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Sun Aug 05, 2018 8:39 am
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Post Re: 37 EFI GTR Issues
Try loosening your gas cap too to eliminate that as a possible issue. My go devil runs like it threw a rod if I don't have the gas cap loose once it gets over 2k rpms


Sun Aug 05, 2018 8:51 am
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Post Re: 37 EFI GTR Issues


Sun Aug 05, 2018 9:40 am
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Post Re: 37 EFI GTR Issues
Ahhhh I see. If you can somehow put a crack in it, try that and see if that helps you. It may be creating a vacuum. One way to tell is if your bulb is collapsed when you are running wot, you arnt getting any air


Sun Aug 05, 2018 4:04 pm
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Post Re: 37 EFI GTR Issues
2015 will for sure need a purchase date to verify warranty. I can about guarantee you will need a harness. Briggs has had 3 versions I know of. Newest ones have tach plugs and rubber dampened fuse blocks.


your 15 can check the codes with a test ight.
There is a wire in the lift pump harness that dead ends at that plug. probe a test light and attach the other end to the starter post.
Turn key on-off and keep it in the on position after 5 sequences and the test light will blink the 4 digit codes
10 blinks is 0. Each blink is the number there is a 1 second pause between digits and 2 seconds between each code if multiple are present.
6 1 means no codes present.

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Mon Aug 06, 2018 5:32 am
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Post Re: 37 EFI GTR Issues


Mon Aug 06, 2018 6:30 am
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Post Re: 37 EFI GTR Issues
Doing some searching online... the wiring harness is Briggs Part# 847336? Shows they are around $220.


Mon Aug 06, 2018 6:43 am
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Post Re: 37 EFI GTR Issues
You are out of warranty. That's the correct harness. Its about a 2 hour job.

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Mon Aug 06, 2018 6:59 am
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Post Re: 37 EFI GTR Issues


Mon Aug 06, 2018 8:43 am
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Post Re: 37 EFI GTR Issues

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Tue Aug 07, 2018 6:29 am
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Post Re: 37 EFI GTR Issues
Well it appears it wasnt the harness. Looking like the fuel line is the issue. Replaced all the fuel line tonight. Ran great in the driveway. Gonna dunk it in the bayou tomorrow and run it but I think it’s good.


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Fri Aug 24, 2018 8:35 pm
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Post Re: 37 EFI GTR Issues
Something that may have already been covered here but drain the fuel and refill with what we here in Michigan call recreational fuel, meaning no ethanol. It's typically 91 octane, I think. I didn't even know I had it around me until recently, but am switching all of my small engine stuff over to it. I read that you replaced the fuel filter, but if the fuel was old, (ie 50ish hours in three years) and the fact that you have a built in tank could mean bad juju in the lines and re-contaminated your new filter... just a thought. I would drain/clean the tank, purge or replace your fuel lines and filter (again), and see where that gets you... It would be a heck of a lot cheaper than a harness, especially if that isn't the problem...

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Sun Aug 26, 2018 1:42 pm
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Post Re: 37 EFI GTR Issues
So, if it were the wiring harness would it definitely throw a code?
Installed all new fuel hose thinking that was it. Ran great up and down the bayou a few runs. I decide to idle thru one of the cuts and check out a few houses. Once I tried to get back on plane it started sputtering and doing the same crap again.


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Tue Aug 28, 2018 10:49 am
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Post Re: 37 EFI GTR Issues
It’s probably he harness. I have a 2015 model with 55 hours so I am just waiting until mine goes out. Maxxis you might know the answer to this, could I call Briggs and have them send me a harness under warranty before mine runs out? Or would I have to take it to a dealer and have them do it? Also being that I put a delta level3 would they not cover the harness even though the harness is a know issue and the mods wouldnt cause the harness to mess up. Thanks


Tue Aug 28, 2018 1:16 pm
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Post Re: 37 EFI GTR Issues
Not always. Usually the older motors have a solid mounted fuse block that rattles the relays and caused bad terminal connections

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Tue Aug 28, 2018 1:16 pm
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Post Re: 37 EFI GTR Issues
For whatever it's worth, I had a 2015 that I sold about a month ago. When I sold it, it had 145 100% problem-free hours.


Tue Aug 28, 2018 6:20 pm
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Post Re: 37 EFI GTR Issues
I’m in the process now of draining all the fuel. Gonna try all new fuel and see if that helps.


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Tue Aug 28, 2018 7:09 pm
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Post Re: 37 EFI GTR Issues
IMG_0025.JPG

Pulled the cover off to look around and found that this had broken at the bracket and was loose. I checked the little black relays inside and the fuses. They looked good and tight so I secured this back in place with some zip ties.


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Tue Aug 28, 2018 7:11 pm
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Post Re: 37 EFI GTR Issues

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Wed Aug 29, 2018 5:51 am
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Post Re: 37 EFI GTR Issues


Wed Aug 29, 2018 6:24 am
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Wed Aug 29, 2018 6:26 am
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Post Re: 37 EFI GTR Issues
Yes, I would replace the harness. your motor will leave you stranded. Those old one are also known to have breaks in the wires going to the high pressure fuel pump. $220 ish for a harness and brackets

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Wed Aug 29, 2018 7:26 am
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Post Re: 37 EFI GTR Issues

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Wed Aug 29, 2018 7:26 am
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Post Re: 37 EFI GTR Issues
also fuel line that's too big usually leak air at the filter that is designed for a 1/4" fuel line. make sure all you fuel connections are solid. Replace the harness.

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Wed Aug 29, 2018 7:29 am
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Post Re: 37 EFI GTR Issues

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Wed Aug 29, 2018 7:40 am
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Wed Aug 29, 2018 7:41 am
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Post Re: 37 EFI GTR Issues
a harness swap takes about an hour if you done it before. First time... about 2.5

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Wed Aug 29, 2018 8:07 am
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Post Re: 37 EFI GTR Issues
Does the harness assy come with any kind of dampeners to help offset the vibration on the ecm/connections? Good luck on the replacement, I hope you get it figured out.

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Wed Aug 29, 2018 8:20 am
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Post Re: 37 EFI GTR Issues


Wed Aug 29, 2018 8:34 am
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Post Re: 37 EFI GTR Issues
Well the harness is installed. I had some guidance and help from a couple guys who have replaced it before. Now I just need another afternoon to run it for a while in the water and see if all is good. Ran fine in the driveway.


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Wed Aug 29, 2018 8:19 pm
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Post Re: 37 EFI GTR Issues
I'm assuming that the harness was the issue?

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