91 115 mariner high rpm problem

[Keep'nitreel]

so here is the deal: motor runs fantastic under 2000 rpms, idles and starts great. when you bring up the rpms to the point when the 3 and 4 cyls. activate it starts to miss and every once in a while the motor has a couple of seconds of strong power but then it goes right back to kind of a bogie misfire. I have replaced plugs and wires and towards the end of last season replaced the switch box due to a no idle problem. Any help would be great. On a side note there is always excess fuel in cyl 4's carb. i do alot of trolling so for the longest time chocked it up to being just build up from long periods of low rpms use but its starting to get kinda bad.

 

[Iceman66]

Re: 91 115 mariner high rpm problem

Time for a carb clean: highspeed jet blocked?

 

[CharlieB]

Re: 91 115 mariner high rpm problem

First verify you have a fat blue arc at each cyl at least 7/16 inch. Disconnect the throttle cable and swing the lever from idle to WOT and back while checking spark on each cyl as a trigger wire can be broken, come apart and fail to fire at some point of its movement.

Once you verify a good spark you need to verify the high speed windings of the stator generate sufficient voltage for the ignition to keep making that hot arc under the increased loads at higher throttle and speed.

CDI Electronics has a very well laid out guide to checking the ignition system, available free here

CDI Electronics Practical Outboard Ignition Troubleshooting

You will need a DVA meter or a DVA Adaptor to use with any Volt/Ohm meter, and a remote starter button or a helper to turn the key.

Repost your progress and any questions.

 

[Keep'nitreel]

Re: 91 115 mariner high rpm problem

o.k so here we go with round two. I tested for spark and got good spark (used a .060 spark tester) But what i failed to mention before was that my tach was on the frits when this whole problem started also my batt gauge they would jump all over the place so in the process of fixing my battery problem i traced it to the main engine harness plug i would wiggle it and the dash gauges would go in and out so I used marine male and female wire terminals and eliminated the harness plug. fixed my batt gauge but i had no tach... the sig wire from the tach was a gray wire re checked my splices and wires good ohm tested wire from dash side of engine harness to tach and wires good. still no tach in this whole process of trying to fix the tach i ran it with the sig wire at the tach disconnected. Well what do you know it dose not go dead after 2500 rpms any more. I do still have a random miss when all four cyls are running and a serious dead spot on three and four right when they kick in but give it a little more throttle and it goes away then just becomes a random miss. i figured that i fouled out the plugs in the process of this whole mess so i replaced them 3 and 4 were washed but that did not fix the prob. so i think that the tach shorted something out! now the Question is what.

 

[Keep'nitreel]

Re: 91 115 mariner high rpm problem

i did install a new tach and it dose not work. here is the wire diagramView attachment wire diagram.pdf

 

[quicktach]

Re: 91 115 mariner high rpm problem

Have you checked the stator and trigger coils ? Rectifier OK ??

 

[Keep'nitreel]

Re: 91 115 mariner high rpm problem

not to sound dumb but how would i do that? i dont have access to a pc so i can not open the cdi file listed above. if i could get a step by step that would be great.

 

[Keep'nitreel]

Re: 91 115 mariner high rpm problem

RECTIFIER'S bad thanks for the help guys. that CDI manual is very nice i printed the whole thing. Never a bad idea to have that info on hand. so do any of you have an opinion as to which company has the better part. CDI, Mallory, or Sierra?

 

[CharlieB]

Re: 91 115 mariner high rpm problem

CDI parts are of the best found on the market.

The 2 + 2 system idles and runs on only the top 2 cyl's until airflow through the carbs increase enough to draw sufficient fuel for combustion to occur in the lower 2 cyl's.

There is an accelerator pump feeding injectors hidden under the electrical plate for those lower 2 cyls.

That accel pump linkage must be adjust exactly as specified in the factory service manual, otherwise you may have that couple of seconds of misfire hesitation when opening the throttle.

Do you have a copy of the factory service manual?

 

[Keep'nitreel]

Re: 91 115 mariner high rpm problem

no i do not

 

[CharlieB]

Re: 91 115 mariner high rpm problem

Send me a PM with a good email address.

Also check out the CDI Ignition Troubleshooting Guide here

CDI Electronics Practical Outboard Ignition Troubleshooting

A spark must be enough to make a hot blue arc across a 7/16 INCH GAP in free air. It takes a lot of voltage to make that big hot spark which is what is needed inside the cyl under the increased compression of full load running at WOT.