mid 80's mariner 115 staight 6 bogs in forward but runs great in reverse

Markrhoades · Aug 14, 2013

If anyone could shed some light on this it would be helpful as stated in the title its a mid 80's mariner 115 I have great power in reverse and it idles in gear I have done the link and sync process which got me where I am now it will take off great for the first run down the river but evetually bogs starts sputtering like its to rich or too lean but only in forward gear reverse it runs like a champ I have adjusted the carbs an eighth of a turn out each time and nothing seems to work after that first good run of about a half mile or so I have good compression and spark I am just not sure what it could be where should I start diagnosing

Markrhoades · Aug 15, 2013

Re: mid 80's mariner 115 staight 6 bogs in forward but runs great in reverse

So no one has any idea where to start with diag

DamianJP · Aug 15, 2013

Re: mid 80's mariner 115 staight 6 bogs in forward but runs great in reverse

Whens the last time the carbs were done %100 and fuel pump?

Does this bog / sputter happen at the same RPM approx?

Reverse is probably not getting high enough in the RPM range to recreate the symptom(s).

Coils can fail at higher RPMs only sometimes and at idle they are fire fine.

What I would do is put inline spark checkers on and check each cylinder , fire the engine up in neutral and bring the RPMs up to the trouble spot to see if each coil is still firing when you get your symptoms. If all light up fire thru the 'trouble spot' then we can focus on fuel delivery.

Hope it helps,
DamianJP

Markrhoades · Aug 15, 2013

Re: mid 80's mariner 115 staight 6 bogs in forward but runs great in reverse

I did suspect the fuel pump at first because the carbs are clean but even pumping the primer bulb while its studdoring does not help and the primer is hard as a rock while its running it takes both hands to even sqeeze it I have not checked to see if it is firing while the studdor happens but at idle with a timing light it has spark on all 6 plugs I will pick up a spark tester on the way home and test it tonight

Markrhoades · Aug 18, 2013

Re: mid 80's mariner 115 staight 6 bogs in forward but runs great in reverse

so I had some time this weekend to test the boat I am getting spark even when the bog happens I had my brother in law spray fuel into the carbs while it was doing it as well but the issue is still there I can put the boat in neutral and rev the motor then quickly put it in gear and it will be able to power up and get on plane for about a half mile or so again could it be the rectifier and the only reason I ask that is when I put my truck battery in it I was able to stay on plane for about 3 to 4 minutes then the motor started to bog out again then I could rev it and when my volt gauge gets up to 16 again it will take off.

Markrhoades · Aug 19, 2013

Re: mid 80's mariner 115 staight 6 bogs in forward but runs great in reverse

Ok so it's not the rectifier I did another test run tonight if I rev it in neutral a few time the let it come back down to idle then slam it wide open sometimes it will take off but some times it won't any ideas of what could be going on with it

Markrhoades · Aug 20, 2013

Re: mid 80's mariner 115 staight 6 bogs in forward but runs great in reverse

Any ideas would be helpful im at a loss all electrical components check out good carbs look to be clean and ths plugs arent dirty I found out it is an 80 model 115 straight 6 serial number 5794820

calvinator · Aug 20, 2013

Re: mid 80's mariner 115 staight 6 bogs in forward but runs great in reverse

Really sounds like fuel delivery. I had a similiar problem on a Merc Mariner a few years back. At higher RPMs, it was fuel starved, sputtered, died. Fuel diaphram was the issue.

Check all your pre-carb fuel delivery. Tank vented, primer bulb not collapsed, filter not plugged, check valve OK, fuel diaphram working. If all that checks out, then you are at the carbs. Floats and high speed jets are next on the list to research.

You mention electrical.... Coils and rectifiers have straightforward multi-meter testing process. Sounds like you did that, but double check so you can cross it off the list and focus on fuel.

Markrhoades · Aug 20, 2013

Re: mid 80's mariner 115 staight 6 bogs in forward but runs great in reverse

Thanks I will try all this stuff tonight and let you know how it goes. I will also double check all the coils and stator and trigger and switchbox bias circuit again just to be sure that it not those. I have an inline filter right after the primer bulb before the pump. should I try taking that out and running it with no filter?

calvinator · Aug 20, 2013

Re: mid 80's mariner 115 staight 6 bogs in forward but runs great in reverse

I would keep the filter. I'm amazed at all the tank crud mine catches. I have a filter between primer bulb and engine chek valve, but on my Mariner there is another filter under the engine cowling too. Maybe you have two filters, maybe not, maybe one is plugged up.

There was a post on here a few weeks ago where someone had a big blob of ethanol goop that clogged his filter. It happens.

Markrhoades · Aug 20, 2013

Re: mid 80's mariner 115 staight 6 bogs in forward but runs great in reverse

could this be a prop issue the reason I ask is the only number on the prop I can make out is a 23 on the front of the prop it is a SS prop but no other numbers can be seen due to the thrust washer wearing them off what pitch should I be running with a 115 mariner 6 cyl on a 84 skeeter sf150 the boats dry weight is 1050 according to skeeters booklet online

Markrhoades · Aug 20, 2013

Re: mid 80's mariner 115 staight 6 bogs in forward but runs great in reverse

Its not the diaphram just chaenked it no holes or and sign of wear oand I checked everything from the tank to the carbs for cracks and leaks and everything looks good and like I said in an earlier post even spraying fuel in the carbs from a spray bottle doesnt help I keep thinking it could be the prop my local shop comfirmed it is a 23 pitch they had a 13x19p aluminum prop I am gonna test tomorrow after work and will let you all know what happens any other suggestions on next troubleshooting steps if the prop doesnt fix it

Markrhoades · Aug 22, 2013

Re: mid 80's mariner 115 staight 6 bogs in forward but runs great in reverse

The prop change helped a little but once it on plane for a few second it bogs back down and sometimes if I let off the throttle and hammer it again it will pick backup and run good for a few more seconds what height should the floats be set on this motor I keep finding different suggestions so if anyone has a manual and could tell me it would be great im also going to try moving the inline filter from before the pump to after the pump

Markrhoades · Aug 26, 2013

Re: mid 80's mariner 115 staight 6 bogs in forward but runs great in reverse

I have been testing electric components again everything in within spec I checked compression cold and all cylinders are within 3 psi of eachother at 120 psi being the highest stator is charging the battery and the is firing even when the bog happens I have removed the inline filter and put 3/8ths fuel line from the tank to the fuel pump but still have the bog is here a way to test the trigger other than just resistance at closed throttle can I open the thottle and still get a reading or is that something that is not possible if it is possible what should my readings be on the multimeter at first pickup and final advance

Markrhoades · Aug 27, 2013

Re: mid 80's mariner 115 staight 6 bogs in forward but runs great in reverse

I really need help on this im at a complete loss carbs are clean gas is new all electrical checks out as per the manual specs new plug and a prop change made it smoother at the bog and I have adjusted the carbs a blade width at a time from 3/4 turn out one at a time all the way out to three turn and nothing gets better or worse could a bad rectifier still charge and give a tach signal but cause this issue?

mercurymang · Aug 27, 2013

Re: mid 80's mariner 115 staight 6 bogs in forward but runs great in reverse

Ok, stupid question but I have to ask. Are your fuel tank vents open?

Markrhoades · Aug 27, 2013

Re: mid 80's mariner 115 staight 6 bogs in forward but runs great in reverse

Yes fuel tank is venting correctly I have even tried taking the gas cap off and running it but does not help anything stator resistance readings are good
Red wire to grd is 158
Red/wht wire to grd is 147
Blu to grd is 6460
Blu/wht to grd is 5900
Between the two yellow wire I get .9

Trigger readings are
Brwn to white is 1390
Wht to purple 1384
Purple to brown 1399

Could the trigger be going out with that high of a reading I have tried heating it up and the resistances drop a few ohms when I do

Markrhoades · Aug 27, 2013

Re: mid 80's mariner 115 staight 6 bogs in forward but runs great in reverse

Also like Isaid earlier the primer bulb always stays hard while its running compression is good all cylimders are within 2 or 3 psi of 120 the carbs have been cleaned and floats set correctly and do not leak and ive adjusted them one at a time like described in the link and sync posts that I have read the only thing I have not tried is replacing the rectifier and buying a new battery but want to make sure that it could cause this issue before I do

mid 80's mariner 115 staight 6 bogs in forward but runs great in reverse

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