1989 merc 115 inline 6 bogging down

[bassman14]

took the boat out last weekend, ran great until...
while on plane the motor died, would restart easliy but would die when engaged to run. Any suggestions on what the issue(s) could be. Thanks

 

[Chris1956]

Re: 1989 merc 115 inline 6 bogging down

It sounds like you got some water in the gas, or some dirt broke loose and clogged your filters or carbs. Try cleaning the filters and pumping the primer bulb while trying to plane the boat. If that works, rebuild the fuel pump. If it does not cure it, post back.

 

[electricjohn]

Re: 1989 merc 115 inline 6 bogging down

I thought the I6 disappeared in 1988?

 

[bassman14]

Re: 1989 merc 115 inline 6 bogging down

it is a 1988 a typo, anyways....
Thanks Chris1956, i did try the primer bulb with no avail. i will look at the filters and carbs.

 

[bassman14]

Re: 1989 merc 115 inline 6 bogging down

Filters and carbs are both in good shape. I broke down and took it to a service center. i am being told that i am not getting spark to three cylinders and they are wanting to replace a power pack. Does this sound right?

 

[Vairpilot]

Re: 1989 merc 115 inline 6 bogging down

The power pack sounds right to me. Exact same thing happened last year on our 1986 90hp I6. We had been out tooling around and had no problem. Shut down to fish for a while. Noticed it was a bit hard to start, but would idle ok once it was running. Died every time it was put in gear. Turned out to be a bad power pack. I bought a pair of new ones off of Ebay and they worked just fine. I've read that you should replace both and not just 1 of them. If they are both original, I'd consider replacing both if you can afford it.

 

[ZigZaggin]

Re: 1989 merc 115 inline 6 bogging down

Sounds right to me as well. I just went through a similar situation on my 1985 inline 6 90 HP which is basically the same motor as the 115 but with different porting. The carbs on these inline 6's are so simple that I have a hard time believing these motors have many fuel issues. With a screen on your tank pickup and also another one inside the fuel pump I think it would take some real neglect to mess up their fuel systems. I store my boat for about 3-4 mos out of the year and have always just added the stabil marine additive to the fuel, run the motor for a while so the carbs are full of the treated gas and left it in while stored. Have never had a problem. Plus, the mercury carb kits are all metal needle seats instead of rubber so wear is minimal.

I originally had a dead #4 cylinder and diagnosed the #4 coil myself. About a week after that I lost the #4 cylinder again. Thinking I might of had a short or something wrong under the flywheel I took it to a mechanic. What I'm finding out is that the ignition systems on these motors seem to be their weakest point. He ran a full ignition system test and sure enough I had a bad switchbox. He charged me $128/piece for 2 CDI switchboxes. I was told it's a good idea to replace them in pairs. Mechanic charged me $50 for an hour of his time to run the ignition diagnosis. Will probably pay him an additional hour to install the boxes and perform a test run on the water. If I'm up and running for the rest of the season $100 + parts is well worth it to me.