How much High Timing can I run?

[4link1955]

I have a 1973 115 Evinrude with a 1977 115 powerhead on it that has been modified with 135 heads, 135 exhaust, and the 135 carbs bored .030" over and a set of weisco pistons. I was wondering how much high timing can I safely run in order to get the most performance out of my motor without burning a piston? Also how id the best way to check it besides hanging off the back of the boat with a timing light in your hand running wide open down the river?<br />Thanks in advance:<br />Jason

 

[walleyehed]

Re: How much High Timing can I run?

in 75' the timing for the 115 was 25 or 26, and I think 28 on the 77'., BUT, you have added alot of parts that I'm not sure of the differance. On those years of engines, it may be exactly the same parts as your 115 had, with the exception of the carbs, which MAY BE slightly larger. <br /> In all honesty, I would contact someone who KNOWS performance modifications. There are too many variables to even guess- the port timing could be different, the deck clearance, Reed size....just too many diff parts to make a guess other than start at 25deg, and don't go any farther until the right answer can be found????

 

[thosch]

Re: How much High Timing can I run?

Walleye is right. A performance person would probably be able to take a crack at this question. Dhadley come to mind. He seems to have a lot of experience in OMC performance mods.

 

[vidar]

Re: How much High Timing can I run?

when you give the engine more air/fuel...the pressure in the combustion chamber will be higher and the flamefront will move faster..ie the ignition time can be retarded a few degrees..i woud try -2 from stock as a start and check plugs after a short run. disconnect gear cabel and throttel link on engine..hook up timing light..start engine..then if you give your controlbox full forward you will get max advancewithout opening throttel on carbs..hooope this can help you a littel..

 

[Mettaree]

Re: How much High Timing can I run?

Jason: Try to find someone that has a load prop to fit your motor. If you know an ob repairman he may have one to help you to check your timimg. That way you could do it in a static mode. ( i.e. motor in tank/drum or boat afloat but tied to dock.<br />Good luck

 

[Hooty]

Re: How much High Timing can I run?

Check the timing with the boat still on the trailer. Back it in until the water pick-ups are submerged, be sure it's secured to the trailer, put it in gear and advance throttle to about 5k rpm and time away. If you have access to a test wheel, us it or a smaller prop.<br /><br />c/6<br /><br />Hooty

 

[Hooty]

Re: How much High Timing can I run?

Time it on the trailer. Back it into water until the prop is submerged, be sure the boat is secured to the trailer, put it in gear and advance throttle to 5k rpm and time away. If you have access to a test wheel, use it or a smaller prop. Be careful and be aware of what you're doing.<br />... and I would set wfo timing to factory specs. No more.<br /><br />c/6<br /><br />Hooty

 

[4link1955]

Re: How much High Timing can I run?

Thanks for all the advice guys!!<br /><br />Jason

 

[MooseHootie]

Re: How much High Timing can I run?

Are you sure you mounted a late model powerhead on your 1973 outboard. I am trying to do this with mine everyone says the mounting bolts are different

 

[CharlesW]

Re: How much High Timing can I run?

Wo-max:<br />Does your statement, "disconnect gear cabel and throttel link on engine..hook up timing light..start engine..then if you give your controlbox full forward you will get max advancewithout opening throttel on carbs", apply to a 1986 40 hp Evinrude as well? Sounds too easy.<br /><br />Charles

 

[CharlesW]

Re: How much High Timing can I run?

It would still be good to know if the timing method suggested by Wo-Max/Motoraddicted applies to a 1986 40hp Evinrude.<br /><br />Charles

 

[Dhadley]

Re: How much High Timing can I run?

If you are running stock jetting stick with stock timing. You can run more timing but you have to dump more fuel to avoid pratice at changing pistons. <br /><br />Good luck!

 

[Walker]

Re: How much High Timing can I run?

CharlesW, the timing linkage is connected to the throttle linkage at the engine block. If you disconnect the throttle cables at the engine then the control box has no effect what so ever on the timing.

 

[CharlesW]

Re: How much High Timing can I run?

Walker:<br />I read his post to mean disconnecting the actual carb shaft linkage and leaving the cables connected. It seems that the timing advance would still be controlled by the actual cable/throttle linkage, but the carb throttle paltes would not open. As usual, I have no idea what I am talking about.<br />It just seems that if this procedure would work, there would be some mention of it in a service manual. I looked and didn't find it in Clymers, Seloc, or the OMC factory manual at my dealers.<br /><br />Charles