1968 18HP Fastwin Irregular Powerloss

[Eagle14]

Howdy all,

Recently my '68 fastwin began performing poorly at high RPM. 90% of its use is trolling and it does it very well even down at 600 to 650. We had finished trolling and throttled up to let the boys zip around before going in. It ran like a champ as normal but after a few minutes I noticed the RPMs fluctuating and a marked powerloss. In times past, on rare occurrences this would happen and a quick flip or two on the electric choke would clear it up. However, this time the problem just progressed as to where I can only reach about 50% of WOT before powerloss.

What I've done:
1. Checked compression. Cylinders within 1-2 psi of each other
2. Checked plugs. Ceramic and electrodes clean and dry, metal slightly damp. Plug gap verified at .030
3. Checked points. Point gap verified at .020 Slight discoloration on 30% of point surfaces. No visible erosion.
4. Checked synchronization. Flipped the cam follower over because of groves starting to form on follower. Verified synch.
5. Always run 100% gas. i.e.: NON-ETHANOL with E/J mix
6. Always store motor after fogging with seafoam (store approx. 4-6 months)
7. Ordered new points and condensers but haven't installed them.

I initially suspected a fuel delivery issue like water in the fuel/carb preventing flow through the H/S jet so I wasted some money on fuel treatment product.

What's next??
1. Carb kit?
2. New plugs to go with new P/C?
3. Fuel lines?

Any and all suggestions are appreciated.

Best Regards,

JR

 

[twocyclemania]

Re: 1968 18HP Fastwin Irregular Powerloss

Could be one of your coils is going. How old are they? It may kick in and out at times as it's dying and you may be running on one cylinder. They can run on one cylinder. When they do they won't reach top speed and idle won't be great. Try disconnecting one plug wire at a time when it's running a 50%. If it's running on one cylinder you'll know which one when you disconnect the plug wire. Also, I had an 18 years ago that on a long run started to run poorly. Long story short; one of the plug wires had deteriorated at the plug boot. I cut a small piece off the end and re-attached and was good to go. If it's not electrical you may be having fuel problems (pump, junk in the carb. clogging the flow).

 

[kbait]

Re: 1968 18HP Fastwin Irregular Powerloss

Choking a warmed-up motor and seeing increased performance is definitely a fuel delivery issue. Choking an already warmed-up motor should flood a properly tuned motor out immediately.

 

[tomhath]

Re: 1968 18HP Fastwin Irregular Powerloss

I assume you have the fuel tank properly vented.

My guess (for what it's worth) is that the fuel pump is getting weak. Could also be a bit of crud in the carburetor's float valve.

 

[racerone]

Re: 1968 18HP Fastwin Irregular Powerloss

Run with a timing light and observe the flashing light when it looses power.----May have one coil sparking to ground in the magneto.-------Can you post pictures of the coils ?

 

[Eagle14]

Re: 1968 18HP Fastwin Irregular Powerloss

kbait: let me clarify that periodically while running at or near WOT the motor would hesitate. During that rare occurrence I would hit the elect choke and it would clear up for a while, like 3-4 months.

I am working on it now and will give the timing light a try. Yes the tank is vented, thank you I've found myself cursing the motor for this reason...

 

[Eagle14]

Re: 1968 18HP Fastwin Irregular Powerloss

Just finished with the test light. Turns out the top cylinder is the culprit for loss of power. Does this isolate the source as a bad coil? Or, should I replace the Points/Condenser first?

 

[oldcatamount]

Re: 1968 18HP Fastwin Irregular Powerloss

Not a bad idea to replace both coils and both sets of points and condensers while you're in there. If one coil goes, the other isn't far behind.

 

[Eagle14]

Re: 1968 18HP Fastwin Irregular Powerloss

Yes, I agree.

I try to replace everything with E/J parts but I can't afford EYE shop. Shipping is more that parts!! Where else can I get E/J parts??

What about Sierra and Teleflex??

 

[oldcatamount]

Re: 1968 18HP Fastwin Irregular Powerloss

Do you have a NAPA store near you?

 

[Eagle14]

Re: 1968 18HP Fastwin Irregular Powerloss

Sure do, just never tried them for outboard parts. Can I give them the OEM part numbers?

 

[oldcatamount]

Re: 1968 18HP Fastwin Irregular Powerloss

Ya, that's what I do. I have found they are reasonable and usually have the parts by the next day. They'll even deliver to you. However, having said all that, it's good to buy here at Iboats if you can.

 

[Eagle14]

Re: 1968 18HP Fastwin Irregular Powerloss

What's your take on aftermarket OEM replacements? Sierra, Teleflex and others... any brand to stay away from?

I will get the coils coming. In the mean time, I've got the new Points/Condensers installed and the motor is running well so far. Once it warmed up I got it to idle down in fwd gear to 500-550. This is where I had it when I first resurrected it and where it ran for many years. Eagle Lake Trout bite best when you troll really sloooooow. So far so good, but I agree that I should replace the coils.

Thanks for all the help guys, much appreciated!!

 

[nwcove]

Re: 1968 18HP Fastwin Irregular Powerloss

OEM Cross Reference

i would avoid sierra impellers.

 

[Eagle14]

Re: 1968 18HP Fastwin Irregular Powerloss

Here's a link showing how it idles with the new P/Cs installed. So far no loss of power but will take the advice and replace the coils. Thanks again all. JR

1968 Evinrude Fastwin 18HP test - YouTube

 

[racerone]

Re: 1968 18HP Fastwin Irregular Powerloss

These coils crack with time or burn out and ground to the magplate.--Remove coils and inspect the bottom of that top one.------- Picked up a very nice 1973 6 HP Johnson.-------I made no attempt to start this motor as I know they all need work.----Both coils were cracked and I have about 20 new coils on hand , so not a problem.----Honed out the cylinders and after assembly it will run like new again.