1977 Evinrude 70 HP, Ethanol, Octane and such...

[rbser]

Hello,
Recently was playing around with my 1972 16' Baja equipped with a 3 cylinder 1977 Evinrude 70 on it...

I noticed that I wasn't getting all the WOT rpm's that I used to get from the OB... seems that the plastic jacket over the wires going up to the timing advance plate, were getting "hung up" on the clamp just above the sync rod...

After opening up the clamp a little to allow the wires to float in the clamp, now my advance plate went all the way to the stop screw with no problem...

Soooo, now here's the question.... when running on 87 octane regular gas mixed with TCW3 oil in correct mix, at WOT I hear what I believe to be "pinging" or knocking....

I know I have no carbon issues on the top end and just put a set of fresh plugs in before yesterday's run...

I have heard through the grapevine (internet) that E10 fuel (obtained at a local automotive gas station on the way to the launching ramp) has a lesser ability to burn as well as older E0 fuel did of the same octane rating.... the BTU's produced by the E10 fuel are measurably lower than those of E0 fuel and have been reported to cause detonation or "pinging" in older engines such as mine...

Other than re-sync-n-link'ng and retarding the timing one revolution of the clamp screw and living with reduced performance of my engine, would anyone recommend using higher octane fuel (such as 89, 91, 95, CAM2 racing fuel) or an octane booster (104+, Gumout octane booster) to stop the pinging??

Would the boosters, or the more expensive fuel pose any problems regarding the health of my old OB??

Anyone else ever have a similar situation and how did you fix it???


Rich

 

[JimS123]

Re: 1977 Evinrude 70 HP, Ethanol, Octane and such...

E-10 provides poorer economy vs. E-0, holds more water and can clean the gunk out of an engine. Octane is not on the list of problems.

I regularly run Evinrudes in the 1964 to 1977 vintage and never had such a problem. I also have an older car (1980) that is very sensitive to pinging - certain types of gas from only certain stations, and this problem goes back 30 years - long before E-10. This car does fine on 87 octane E-10.

 

[rbser]

Re: 1977 Evinrude 70 HP, Ethanol, Octane and such...

Understood, I also run older vehicles on E10 and other than the things you mentioned haven't had any issues with it. I was asking if anyone had similar experiences with fuel/engine/pinging. Here on Long Island the fuel supplies are subject to change and I was looking for a longer term solution other than retarding the timing on the OB.

Rich.

 

[gm280]

Re: 1977 Evinrude 70 HP, Ethanol, Octane and such...

Actually E10 or even E15 fuels are less prone to pre-ignition then E0 fuels are. So when you talk about your engine pinging at WOT with E10 mixed fuels, you may need to read (with a timing light) the exact advance timing you are running. It could be too far advanced from original specs now... And you can prove that one way or the other by not changing anything (as far as the timing goes on the engine) and swap your fuel over to E0 fuel. A lot of Pure Gas Stations (at least around me) sell ZERO ethanol fuels still and you could buy some of that fuel to see what happens at WOT then... Just an idea... :watermelon:

 

[rbser]

Re: 1977 Evinrude 70 HP, Ethanol, Octane and such...

In the Long Island area I haven't seen a single gas station selling E0 gas. Not that there might not be a few marina gas docks that have it available here, but I usually purchase my fuel in automotive gas stations. I will check the timing with a timing light the next time I am out. If I remember correctly max advance is 17 degrees BTDC.

Rich.

 

[Silvertip]

Re: 1977 Evinrude 70 HP, Ethanol, Octane and such...

Ethanol has a higher octane than regular gas. E-85 for example is 104 octane. People confuse octane with power and that is simply not the case. Higher octane reduces the tendency for an engine to ping or pre-ignite fuel. That also means it is harder to actually ignite. The benefit of higher octane is that it allows ignition timing to be advanced to take advantage of the higher octane which MAY allow the engine to produce more power. In engines with knock sensors, timing can be advanced automatically to the point just short of preignition. Unfortunately - ethanol does indeed reduce fuel economy somewhat since more of it is needed to produce the same power. Your older engine will suffer from degraded rubber parts unless they are replaced with ethanol tolerant replacements.

 

[metriccrescentwrench]

Re: 1977 Evinrude 70 HP, Ethanol, Octane and such...

ethanol does indeed reduce fuel economy somewhat since more of it is needed to produce the same power.

But it's such a minor difference I doubt it would be noticed. I did the math on E10 vs straight gasoline a while ago, and while I can't remember the exact number it was very small, something like 1 or 2 percent as I recall.

As far as the original question of a 'pinging' noise at WOT, I have an '81 90 HP Johnson that makes a noise similar to that. It's been doing all 7 years that I've had it with no ill effects (checked compression a few months ago and it's unchanged from when I first got the engine).