Mariner 100 1988 bogging

[Barton3000]

Hi,
I?m new to this forum.
I?m from Sweden and i have searched all swedish forums for help on this problem, with no luck.
My Mariner 100 1988 (4-CYL) can run forever on idle and up to about 1800 RPM then it starts to bog down, as it cannot decide if it should run on 2 or 4 cylinders.
Rpm falls and it starts to shake very much.
Does anyone here know what controls the shift between running on 2 or 4 cylinders.
It has a new (red) stator with the black box. and a new CDI box.

How the heck does it know when to run on 4 cylinders or not?:redface:

Regards: Magnus - Sweden

 

[sschefer]

Re: Mariner 100 1988 bogging

Hi,
I?m new to this forum.
I?m from Sweden and i have searched all swedish forums for help on this problem, with no luck.
My Mariner 100 1988 (4-CYL) can run forever on idle and up to about 1800 RPM then it starts to bog down, as it cannot decide if it should run on 2 or 4 cylinders.
Rpm falls and it starts to shake very much.
Does anyone here know what controls the shift between running on 2 or 4 cylinders.
It has a new (red) stator with the black box. and a new CDI box.

How the heck does it know when to run on 4 cylinders or not?:redface:

Regards: Magnus - Sweden

Oh Yeah, I got this one guys...... The way this engine is supposed to work is on a very fragile theory that the fuel mixture is not rich enough to burn but remains adequate to lubricate up to around 1800 rpms. At that point the throttle plates on the lower two carbs,which are tuned at the factory, are supposed to be open enough to provide enough fuel for combustion. However, the accelerator pump plays a big part in this in that it feeds two injectors on 3 and 4 that have check valves in them that can't open until fuel pressure is adequate. These two injectors are located in the block and are visible and accessible if you remove the electrical plate. There is also a hidden fuel filter between the accelerator pump output and the injectors. It is accessible if you remove the oil tank.

So, remove the oil tank and the electrical plate and then change the filter followed by removing the injectors, dissassembl them and clean and lube them with wd-40. Test them with a vacuum gauge to make sure the check valves are functioning correctly. Replace the injectors and the tubing that connects them to the "T" from the accelerator pump. The fuel line size is 7/64" and make sure you get fuel rated and not windshield washer hose.

Once you have all that done, rebuild your fuel pump and accelerator pump and you should be back in business. Just an FYI, doing only half the job will only result in frustration so do the whole job and you'll be back to great boating in no time.

 

[Barton3000]

Re: Mariner 100 1988 bogging

Great
Thats precisely the answer i was looking for, Thank you very much.
I will be on to it as soon as possible.
Thank you so much for your effort and time to write down such a detailed answer.

My best regards to you/ Magnus - Sweden.

Its a pity the boating season is almost over here in sweden.

 

[sschefer]

Re: Mariner 100 1988 bogging

One last little tip. The fuel line that goes to the injectors loops back into the main fuel line before the fuel pump. This is wierd but there is a plug inside the tube immediately after the last fitting on the injector side. It needs to be there so if you think the lower tubing going under the lower carb to the main fuel line is plugged, you're right and it is supposed to be.

 

[Barton3000]

Re: Mariner 100 1988 bogging

Are you still here?
One more question about this.

If the injectors provide extra fuel for 3 and 4 while accelerating,
what gives fuel to 3 and 4 while the engine is on idle?
if the carburetor is completely shut and there is no idle circuit on the lower carbs.
Are they adjusted to let some fuel trough even if they are closed?

 

[sschefer]

Re: Mariner 100 1988 bogging

Are you still here?
One more question about this.

If the injectors provide extra fuel for 3 and 4 while accelerating,
what gives fuel to 3 and 4 while the engine is on idle?
if the carburetor is completely shut and there is no idle circuit on the lower carbs.
Are they adjusted to let some fuel trough even if they are closed?

The carbs will spray adequate fuel for lubrication but not combustion. There is a factory set air mix screw on the upper left side of the carb. It has a red seal over it and is never supposed to be adjusted. The lower carbs do not have idle mixture screws either.

It's one weird setup if you ask me. My thoughts are that it is totally dependent on the quality of the available fuel and very precise timing.
I've recently dropped my initial timing to 20deg max at cranking speed (300 RPM) the previous tech note say's to set it at 22 and thats well down from the original that say's 27 or the sticker on the attenuator cover that say's 25.

Pretty much, once you have the injectors working properly the rest is voo-doo. Just keep playing with small timing changes and idle screw adjustments until you find the sweet spot.

 

[Barton3000]

Re: Mariner 100 1988 bogging

Thanks for your reply,
Yes it is one weird setup, I agree.
I have rebuild the fuelpump and replaced both fuelfilters and today i received the kit for the acceleratorpump

I ordered new injectors a few days ago as one of them was leaking constantly, thats why it took so much fuel.
Number 4 was completely soaked.
Hopefully I can give it a try this weekend.
Wish me luck.
About the sparkplugs they are NGK BPR7-HS10 are they not supposed to be 8 in heatrange?

I wish you the best/ Magnus-Sweden

 

[sschefer]

Re: Mariner 100 1988 bogging

Thanks for your reply,
Yes it is one weird setup, I agree.
I have rebuild the fuelpump and replaced both fuelfilters and today i received the kit for the acceleratorpump

I ordered new injectors a few days ago as one of them was leaking constantly, thats why it took so much fuel.
Number 4 was completely soaked.
Hopefully I can give it a try this weekend.
Wish me luck.
About the sparkplugs they are NGK BPR7-HS10 are they not supposed to be 8 in heatrange?

I wish you the best/ Magnus-Sweden

I run 8's in mine. I don't know what it called for originally but that's what they say to use now. NGK BPR8-N-10 gapped at .040 but please double check with NGK first, I don't want you to go on my word and burn a hole in a piston.