gasolin octane

[riv56]

Hi fellas, I am kind of new to boating an I just bought a 1987 bass tracker with a 70 h.p. mercury on it, my question is the boat runs fine at high rpms but it is a little hestitant at taking the gas from an idle also it idles pretty rough even after the motor is warmed up, if I use gasoline of a higher octane than regular which is 87 here, is there a chance it will run any smoother an take the fuel a little better. Any help is appreciated.

 

[EJ3]

Re: gasolin octane

I don't think your problem is the octane of the gas. It sounds like a fuel delivery problem. I have a 60hp Merc and 87 does me just fine. Has the motor been sitting with gas in it for a while? This could cause a gunky film in the carbs, restricting the gas flow. A small hole in one of the gas lines? Misadjusted idle spped screw in the carb? It could be a number of things, but it definetly sounds like fuel delivery is your problem. Do a search on Seafoam on this forum.

 

[DJ]

Re: gasolin octane

I don't think your problem is the octane of the gas. It sounds like a fuel delivery problem. I have a 60hp Merc and 87 does me just fine. Has the motor been sitting with gas in it for a while? This could cause a gunky film in the carbs, restricting the gas flow. A small hole in one of the gas lines? Misadjusted idle spped screw in the carb? It could be a number of things, but it definetly sounds like fuel delivery is your problem. Do a search on Seafoam on this forum.

Octane isn't your issue. You have other issues, as stated above.

87 is recommended.

 

[DJ_Allatoona]

Re: gasolin octane

I got an '86 motor in January, had similar problems as yours. Definitely fuel delivery. I replaced the fuel line/bulb, added a glass inline filter, and replaced the fuel pump diaphram. All very easy. Also, throw in some new spark plugs just for icing on the cake. If your carbs are clean, you'll likely see some noticeable improvement.

 

[EJ3]

Re: gasolin octane

WOW, my first quote, a shining moment for me! Especially since a veteran agreed!!

Anyways, I thought of something else. I have ready some posts where Merc owners have adjusted their idle slightly higher for this very reason, low idle.

 

[j_martin]

Re: gasolin octane

If it idles rough, something's mechanically amiss. Could be anything from a dirty carb to worn reeds to a worn out motor. If it were mine:

1. I'd run a compression test on it to see if it's even fixable. If it comes up low, have a mechanic borescope it. If it looks OK, look up the sea foam decarboning on this site and do it. Might ressurect it. (how's that for a Good Friday comment)

2. I'd throw a set of plugs in it, especially if the old ones looked fouled or old.

3. Check out the link n sync. If you set that up right, and it won't idle, then

4. Clean the carbs and throw in a fuel pump kit.

You need the factory repair manual to do this stuff, but it's basic back yard mechanic level work.

hope it helps
John

 

[riv56]

Re: gasolin octane

thanks for the help, I will try some of these ideas, but that makes more questions, what is link an sync?

 

[j_martin]

Re: gasolin octane

thanks for the help, I will try some of these ideas, but that makes more questions, what is link an sync?

Carburettor and timing linkage adjustment. Get the shop manual for your motor, preferrably genuine mercury. It's in the book.