Proper Plugs for 1975 135HP

[Randyg123]

I have seen quit a bit of posts regarding which plugs to use as replacements in the older engines. There's enough variances in these to prompt me to ask this question. It seems pretty common to agree that the UL77V (or equiv) is not really optimum unless high-speed use is the norm. But with the L77JC4 (or QL77JC4) should the gap be set at 0.030 or 0.040?

I have them at 0.030 right now because I thought this was an 85HP.

 

[Gary H NC]

Re: Proper Plugs for 1975 135HP

Here is a great spark plug guide,The first plug number listed is the preferred plug,
http://www.boatsetup.com/SparkPlugChart.html

it shows these only,UL77V or L16V Surface Gap

 

[Dhadley]

Re: Proper Plugs for 1975 135HP

On that motor on todays fuel I'd use the (Q)L77JC4's. The gap, either .030 or .040 depends on what you do with the motor. You might even set it at .035 and go boating.

Regardless, .30 is a bit wide.

 

[Randyg123]

Re: Proper Plugs for 1975 135HP

On that motor on todays fuel I'd use the (Q)L77JC4's. The gap, either .030 or .040 depends on what you do with the motor. You might even set it at .035 and go boating.

Regardless, .30 is a bit wide.

Ooops! I meant 0.030. I guess I should edit that.

But hey, it's only an extra zero, what harm could that be?

What would be the reason for selecting either one?

 

[F_R]

Re: Proper Plugs for 1975 135HP

Back around 1970, they came out with the L77J4 (Now L77JC4). That plug was a godsend to us outboard mechanics that were going nuts trying to make motors run on the surface gap plugs that came with the motors and shown in the plug charts.

More recently, the Q was added to the number. That Q means it has an inductive (not resistive) radio noise supperssor built in and are the current choice.

 

[jtexas]

Re: Proper Plugs for 1975 135HP

.040 if you do mostly trolling, discourages fouling