115 Mercury Optimax problem

[MR. Bass]

I have a 115 optimax 2004 (DFI) run rough at Idle, Checked fuel pressure reading 30psi should be reading 88 psi to 92 psi, clean water sapartor out found, parts of old fuel line in chamber where filter is clean filter and chamber, looked at both fuel pumps screen they are clean. Changing the filter will this help and does anyone know what the reading on the pumps should be checking with a meter to see if on had failed.

 

[steelespike]

Re: 115 Mercury Optimax problem

Welcome,your in the wrong section.This is boat topics 'not engine topics'.
You will get much better help in the Mercury outboard repair forum.
good luck.

 

[Philster]

Re: 115 Mercury Optimax problem

When you get over to the Merc Outboard section, be ready to understand Direct Injection. Your engine drives a belt, which drives a compressor which helps inject fuel directly into the combustion chamber... so just be prepared in case the issue is more complicated.

Read up on Direct Injection. Can't hurt. http://airinjectors.com/aircompressors.html

 

[MR. Bass]

Re: 115 Mercury Optimax problem

When you get over to the Merc Outboard section, be ready to understand Direct Injection. Your engine drives a belt, which drives a compressor which helps inject fuel directly into the combustion chamber... so just be prepared in case the issue is more complicated.

Read up on Direct Injection. Can't hurt. http://airinjectors.com/aircompressors.html

I have over 80 psi on air compressor so I don't think this is the problem. Thanks

 

[Faztbullet]

Re: 115 Mercury Optimax problem

First off get rid of the fuel line, Merc had problems with the earlier lines, if it has RED writing imprinted on it,its bad! Since you found these pieces in the water separator ,these are the first things I would check if you brought it to my shop:Fuel supply line, mechanical fuel pump for debris damaging /holding check valve open since debris came thru it to get to separator, replace water seperating filter to insure not clogged internally and finally the inlet needle of VST float as if any of the above fuel flow to VSTwill be restricted, causing the high pressure pump to aerate/cavitate due to VST is not filling and result in low fuel pressure at schrader valve .

 

[MR. Bass]

Re: 115 Mercury Optimax problem

First off get rid of the fuel line, Merc had problems with the earlier lines, if it has RED writing imprinted on it,its bad! Since you found these pieces in the water separator ,these are the first things I would check if you brought it to my shop:Fuel supply line, mechanical fuel pump for debris damaging /holding check valve open since debris came thru it to get to separator, replace water seperating filter to insure not clogged internally and finally the inlet needle of VST float as if any of the above fuel flow to VSTwill be restricted, causing the high pressure pump to aerate/cavitate due to VST is not filling and result in low fuel pressure at schrader valve .

Thanks I have replaced the fuel line and bulb, have not replaced filter yet that was my thought, Did not see any debris in second chamber were low fuel pump is. I think that is what your calling the VST Float chamber.

 

[MR. Bass]

Re: 115 Mercury Optimax problem

Also I was wondering with the question come more even if I didn't have a fuel pressure problem could a low voltage Battery cause a Optimax to run rough at idle?

 

[Faztbullet]

Re: 115 Mercury Optimax problem

Yep!!!!

 

[jeffersondodson561]

Re: 115 Mercury Optimax problem

If you were getting your reading from the vapor seperator you were reading the low pressure (boost) pump, which is correct for that pressure. You should post your serial number because your air pressure might need to be 95 +/- 1 psi and your fuel pressure should be around 110psi. But I doubt you would be able to check it without the special fuel gauge attachment.

 

[MR. Bass]

Re: 115 Mercury Optimax problem

Ok replaced filter, hose, bulb, gas and high pressure pump still not running right. belt looks like it may be worn cracking and plugs my be fouled, is my next step.