73 Evinrude 6hp power struggle

[crxess]

Now I'm lost. Motor lays flat around 2000 RPM, maybe less. Nothing increases RPM except running in neutral.

Basstender 10.2 rated 7HP Max

Work done:
Head Gasket replaced
Thermostat replaced
Impeller replaced
Carb rebuilt w/kit
Points set to .020
New plugs .030
lower oil changed
Replaced tiller arm
Prop tightened

Test:
Compression 60/60
Fuel pump flows well
Bulb pumps up tight and holds
Good spark
Idle setting decent

Power test under load:
Pull lower plug wire motor lays down - keeps running
Pull upper plug wire motor lays down - keeps running
Good hot spark. refired either plug from 1"+ knocked me silly.
Spray pre-mix into carb motor bogs down
Spray very lightly into carb RPM drops.

Noticed slight wear on throttle cam. opened carb further by hand - no change.

At this point I will gladly entertain any and all suggestions, speculations......etc.

 

[jonesg]

Re: 73 Evinrude 6hp power struggle

Given all that, I'd say its on the richer side.
How do the plugs look after a 2K rpm run?

One thing we used to do with racing engines was pinch the fuel line briefly to lean the mix , it will indicate a rich condition by picking up the rpms.

You sure the float isn't upside down in the carb?

 

[crxess]

Re: 73 Evinrude 6hp power struggle

Plugs are staying clean. 2 1/2 mile - 1 hour run @ wot.
Float is correct. Deep reach into bowl. Starts easy ,1-2 pulls.
I will try pinch test today and see if any significant change.

What would an internal exhaust leak do or act like?( Grasping at straws )

 

[crxess]

Re: 73 Evinrude 6hp power struggle

No luck yesterday.

Winds were up, current was strong and wife was on board.

First thing I noticed on start up was it was idling smoother than previous trips. Left the ramp heading down river/down wind. RPM seemed higher and boat moving a bit faster.
Brought it to an idle and putted around a bit. Turned upriver and opened it back up. RPM came back to about the same as down river.

Seems to be running a little over 1/2 RPM now.

My thinking is - correcting the loose Prop stopped wobble and allowed increased RPM/Speed but motor problem still exist.

Didn't attempt pinch test under these river conditions.

 

[F_R]

Re: 73 Evinrude 6hp power struggle

No solutions but just a couple of thoughts. First is, I have no idea what a Basstender boat is. Has the motor ever ran right on it? Maybe it is the boat and not the motor?

Second, running at half power almost always is a result of running on one cylinder. Your pulling the plug wires contradicts that. Have you tried pulling an grounding one at WOT or only idle? Could be losing it at WOT.

 

[crxess]

Re: 73 Evinrude 6hp power struggle

Thanks F_R

Bass Tender is a small Plastic Trihedral hull boat. Not a planing hull, but still should allow motor to reach operating RPM, at least with just me on board.

1 person no gear, 2persons loaded - speed changes very little but RPM does not.
Me alone 135lbs, 2 gal fuel, 50 lbs of trolling battery/motor/tools.

Definitely not losing spark at WOT - ouch, ouch and ouch.

 

[crxess]

Re: 73 Evinrude 6hp power struggle

Found more questions than answers. Posted it a new thread. I'll save and update this one on what has been done and did/did not help.

 

[crxess]

Re: 73 Evinrude 6hp power struggle

Back with more info.
1)Ran a decarb on motor. Still ran about the same.
2)Repaired/reset Throttle cam - worn down.
3)Repaired Follower - grooved.

4)Replaced Head today due to Heli-coil issues.
Rechecked Compression.
Now 80/80 Looks like seafoam helped.
5) inspected both plugs. Both look equal in operation/color. One electrode was off center. aligned and re-gapped.

Still waiting on lower pitch prop to arrive.

May try it out again this afternoon if weather holds.

 

[crxess]

Re: 73 Evinrude 6hp power struggle

Finally results I can live with.

After getting everything else tested/repaired - still had poor performance. A few hundred rpm gain at best.

Installed new lower pitch prop and took it out today.

RPM approx. 4000
Speed 8 mph into wind and current with full load. Up from original 2.5 mph.

Obviously the boat design falls under Working/Heavy class due to non-planing Hull Design.