Need opinions about 1973 18hp Evinrude-UPDATED

[G DANE]

Re: Need opinions about 1973 18hp Evinrude

Re: Need opinions about 1973 18hp Evinrude

I Would start with a spark test, I battled with a 1973 25 HP almost an entire spring. The true problem appeared when I made a spark test, makin both sparks jump longer and longer gap, just to find one was weak. Turned out that one of the new condensers were weak. With that fixed and coils as near to magnets as possible, and a correction of armature plate wobble, it ran like new and still does. Before it used to shake and cut out at iddle, hisitate on low end at hole shot, and plugs shoved it loaded up.

 

[dwagner47]

Re: Need opinions about 1973 18hp Evinrude

Re: Need opinions about 1973 18hp Evinrude

G DANE:
Your advice rings true somewhat as once I was trying to do a crude spark test and I observed that the motor idled better when I held the spark plug boot around an inch away from the plug versus when it was on the plug snug. This confused me as I didn't know if it pointed to a spark problem or timing issue. As I had already replaced the points & condensers and set timing carefully I didn't think that would be the problem. I assume I can do a spark test by putting something conductive in the spark plug boot and observe the spark jumping to the plug while running? Doing this what constitutes a weak versus strong spark? How can I measure the gap between the flywheel magnet and sensor coil? I was just lining up the frame of the sensor coil with the bosses on the armature currently.

 

[iwombat]

Re: Need opinions about 1973 18hp Evinrude

Re: Need opinions about 1973 18hp Evinrude

Almost . . .

You'll want to watch the spark jump to the block, or something grounded to the block, not the plug end.

Something like this, or you can just make your own.

 

[iwombat]

Re: Need opinions about 1973 18hp Evinrude

Re: Need opinions about 1973 18hp Evinrude

In case you haven't seen one before. That's a ground clip at the bottom and an adjustable screw in a c-mount, with a spark plug sized connector on the very top.

You attach the clip to the block, adjust the screw to the correct gap, and attach your plug wire to the top.

 

[iwombat]

Re: Need opinions about 1973 18hp Evinrude

Re: Need opinions about 1973 18hp Evinrude

All that being said, you can also just shove a bolt into the spark plug boot and attempt to hold it a fixed distance from the block. It's far easier using a proper tool though.

 

[dwagner47]

Re: Need opinions about 1973 18hp Evinrude

Re: Need opinions about 1973 18hp Evinrude

It looks like the tool may prevent some shocks.

 

[casi77]

Re: Need opinions about 1973 18hp Evinrude

Re: Need opinions about 1973 18hp Evinrude

what about doing a de-carb & can of seafoam in the tank and run it..?

It looks like the tool may prevent some shocks.

 

[tashasdaddy]

Re: Need opinions about 1973 18hp Evinrude

Re: Need opinions about 1973 18hp Evinrude

i had until this weekend a '1955 15 hp rude. once i use the idle settings in the post, it never sneezed, coughed, or hesitated. you would have thought it was brand new.

 

[F_R]

Re: Need opinions about 1973 18hp Evinrude

Re: Need opinions about 1973 18hp Evinrude

Ahem.....your 1955 dumped the crankcase drains into the exhaust housing and lake. It was done through passages drilled in the crankcase casting. No hoses. That's one reason they ran so well compared to the '73.

 

[BF]

Re: Need opinions about 1973 18hp Evinrude

Re: Need opinions about 1973 18hp Evinrude

I just wanted to say that I've followed this thread with interest. I have a 1970 25 hp rude that runs great, except at idle. I've cleaned the carb (new float etc etc), re-did the ignition, replaced thermostat & water pump... none of which made any difference to the idle. The idle mixture can be adjusted from too rich right through to too lean (sneazing out/die) without the discernable "sweet spot" my other motors have. When it's set up the best that it can be, it doesn't idle down great, and will still sneeze itself out every 5 min or so.

I've just lived with it for a couple years, and used my 6 hp (on boat beside the 25) for trolling... It'll putt putt for the whole day without a hiccup.

I'll check into the recirc hose next spring... I'm already running a collection bottle on my old chrysler 45... otherwise it leaves a nasty gas/oil slick beside the dock.

Anyway, just wanted to let you know I've also found this thread interesting.

 

[iwombat]

Re: Need opinions about 1973 18hp Evinrude

Re: Need opinions about 1973 18hp Evinrude

The old flat-track racers I used to ride needed to run a collection bottle for the total-loss oiling systems. There's several tidy little commercial options available for around $50 if you look on some of the vintage racing sites.

 

[DJ]

Re: Need opinions about 1973 18hp Evinrude-UPDATED

UPDATE INFO. from dwagner47


Thanks to all those that responded to my previous post. With wonderfull weather (60 degrees, sunny, no wind) here in Michigan over the Thanksgiving holiday I got a few chances to tinker with my motor before putting it away. My issues were:
- Hesitation upon acceleration.
- Running rough and missing at idle.
- Starting when cold but then dying and hard to start.

From tinkering I found a few things. First of all the motor seemed to be running cold in a test bucket. The discharge water was cold. I put the restrictor back into the bypass passage as suggested by the dealer bulliten and the motor ran better an idled right down. When checking cylinder head temp after running at open throttle with an infrared thermometer I get 150 on top cylinder and 140 degrees on the bottom. After idling for a few minutes it reads 125/115 degrees. Is it normal to run cooler when idling? Is it normal for top cylinder to be normal while bottom cylinder is cooler? The water in the lake is pretty cold now (smaller lakes have been freezing lately) so I may have to evaluate the temp again next summer.
Second, I adjusted the flywheel/carb synchronization so the throttle plate is getting actuated sooner. Hesitation is almost gone! I may double check he timing and the synchronization again to see if I can improve things further.
After doing the above 2 thing now I can set the idle mixture a little richer so that lean sneeze is now gone.
So motor is running much better. The only issue is slight hesitation after idling and if letting the motor idle for a few minutes it seems to cool down and load up a little bit (bottom plug seems a little fouled).

Only thing I don't get is why the motor seems to run rather cold. I replaced the thermostat and I can see that it opens right at 150 degrees. Without the restrictor in it runs really cold now, never warning up at all at idle.

As suggested before I'd like to evaluate spark strength. All ignition parts are new. I haven't found a simple spark gap tool at the auto parts stores yet.

Cold weather is just around the corner so I'll probably put the motor in the crawl space soon and then tinker more next Spring.