1997 Mariner 200 EFI running rough

1997 Mariner 200 EFI SN OG468820 would intermittently have a rough idle and when you would throttle up at the lake it would bog. This happen last year and I changed all the fuel lines and filter and plugs. It was fine untill a couple days ago and did it again. Got it home and it would barely crank and run and would not throttle up. The Fuel pressure was at 39 psi with the pump running and 36 when not running.I changed the plugs to NGK BUZ8H Resistor plugs from BU8H. I checked the spark with a timeing light on each plug wire and had fire. I then started checking connectors. I unplugged the connector from the ECU to the main harness. It is just a rubber push together connector with long pins. All the pin looked good with no burns. When I plugged it back together it cranked and ran great at home. I took the plug back apart and spread the pin a tiny bit with a knife blade and put it back together and tyrapped the connector together so it could not work loose. It cranked and ran great at home. I guess I am ready to put it in water and try it again. Any thoughts of anything else to check? It is so intermittent I still am a little concerned if that was the problem. By the way it is on a Nitro 896 bass boat with very low hours. I bought it new and did not use it a lot untill I retired last year.

Re: 1997 Mariner 200 EFI running rough

Well, took it out on the lake and it ran perfectly except one time for a 1/4 second it glitched. The RPM dropped suddenly and then picked right back up. It only happen that one time. It makes me think something is still going on. Question, does the ecu on the 97 Mariner 200 EFI store codes. I was thinking of getting the scan tool and take a look at the the sensors. I guess I will go back through the connections one more time. I was thinking that if a sensor failed that it would not be intermittent. Any thoughts, I just don't feel comfortable that the issue is fixed.

Re: 1997 Mariner 200 EFI running rough

EFI's do not like old fuel. Stabilizers prolong fuel shelf life only for a short time, a few months.

If you have old fuel, drain it out, drain the VST, use the old fuel in your truck or lawn mower.

If you continue to have low speed problems you may need to send your injectors in to Tony Brucato for proper cleaning.

Re: 1997 Mariner 200 EFI running rough

it is fresh fuel and I put Quicksilver fuel conditioner in at ever fill up. The engine runs great and then suddenly it will mess up and then start running great again. I am fairly sure it is an electrical problem. I don't think the injectors are clogged .when it is working it run and idles great. It starts with a quick bump to the starter. Thanks for the suggestions.

Re: 1997 Mariner 200 EFI running rough

get the injectors flow tested,especially if you never have,you run one lean and bye bye mota' !,those were known for that issue.

Re: 1997 Mariner 200 EFI running rough

Definatly found the problem. The Blue wire to the injector plug in the wiring harness just pulled loose with a little tug. That means the #3 and #4 injector was intermittenly not firing. I pulled the pin out of the connector and soldered the wire into it and reinstalled it. Concerned that there may be cylinder damage I ran a compression check. #1 112psi #2 105 #3 120,#4 115 #5 120 #6 105. This was on a cold. Engine is running good and started with one bump of the starter in the driveway. Hopefully this will resolve the issue. I will definatly get the injectors flow tested at the next tune up in the spring. I just hate to mess with it now it is running so good, it is fishing time.

Re: 1997 Mariner 200 EFI running rough

Hey there, so is the problem still fixed? Im experiencing the same issue

Re: 1997 Mariner 200 EFI running rough

Yes,it is fixed. I have not had another issue