Mercury Optimax 75 fuel question and question about shifting forward reverse

AZcamperguy

Petty Officer 2nd Class
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Feb 28, 2009
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130
I just got this boat and the previous owner told me to only use expensive gas. I looked in the ,manual and it says 87 octane is fine. Now, if he has been using high octane the since he's had it for the last few years does it matter if I use lower octane or do I need to put the higher in? Also, can I use seafoam and marine sta-bil as well as the mercury suggested fuel additive all at the same time?

He also told me that when shifting from forward to reverse and back to always do so quickly so as to not grind gears? What if I am trying to make minor adjustments like when approaching a dock?

My previous motor was a tiller and an older one at that so this is new to me. Thanks!
 

Philster

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Sep 15, 2009
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Re: Mercury Optimax 75 fuel question and question about shifting forward reverse

If it calls for 87, you can use that. It does not matter if he ran premium.

When shifting from NEUTRAL into gear, or from IN GEAR into NUETRAL... always do so quickly and deliberately. You never go forward to reverse or reverse to forward. You move it quickly/deliberately from neutral or into neutral. You never slide the shifter softly/slowly to feather it.

Approaching a dock, you move quickly/deliberately to nuetral; then you can move deliberately/quickly to reverse, just as an example.

If Merc calls for a fuel additive, then you use one (I believe they do for all Optis) It's either to control carbon, stuttering, start-up, low-speed operation or other issues with modern 2-stroke engines.

.
 

AZcamperguy

Petty Officer 2nd Class
Joined
Feb 28, 2009
Messages
130
Re: Mercury Optimax 75 fuel question and question about shifting forward reverse

Thanks Philster. That makes sense about the shifting now. I was a little confused about what he was saying.

What about putting in the seafoam and marine sta-bil at the same time? No issues as far as that is concerned?

I always used Sta-bil on my other one but on this one the fuel gauge appears to be stuck. I was thinking the Sea Foam may unstick it. My buddy said on his boat that the gauge was stuck and he put a whole bottle of Sta-bil in it and it started working.
 

Philster

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Joined
Sep 15, 2009
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3,342
Re: Mercury Optimax 75 fuel question and question about shifting forward reverse

Well, I never heard of Stabil fixing a gauge or the sender unit before. Check out the electronics section here, or maybe someone will chime in on how to trouble shoot a bad gauge. It's easy. I don't know the exact details.

Who said to put Seafoam and Stabil in it? Oh, plus the Merc stuff? BAH! Pick one. If the Merc stuff is available, just grab that. I use Stabil. Mercury just makes a general recommendation to use a fuel stabilizer.
 

AZcamperguy

Petty Officer 2nd Class
Joined
Feb 28, 2009
Messages
130
Re: Mercury Optimax 75 fuel question and question about shifting forward reverse

OK, I'll just throw the sea foam in there since I already bought it and then I will get some more of the merc recommended stuff and use it with sta-bil. I will take a look at the gauge and sender too. Thanks for all of the help Philster
 
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