Evinrude 235 boggs out in WOT

[hotrodjohn71]

I had some issues with my motor on the lake today and Im hoping I might get some advice before I take it into a shop.
The problem is bogging out and cutout at wide open throttle.
It has run well in the past. Its possible that today I didnt let it warm up enough at the dock before pulling out but I dont recall warmup being an issue in the past. I also noticed today that several times after stopping and shutting it down a while, it will start and idle fine, but seems to need a while to warm up before it will rev up enough to get on plane and will just cutout when throttled so I back it off the throttle and eventually after a few tries were cruising fine.
It will cruse around all day at 3000-3500 RPM's, but when I go wide open, it boggs out and sometimes just cuts out so I pull back on the throttle and its Okay again in the lower RPM's (3000-3500)
This bogging happens about 75% of the time when I go WOT. Its kind of like someone just turned a switch off. Not really like a miss fire issue, but like a cutout issue. I pull back on the throttle and were okay again. There were a couple times it went all out and ran without bogging out.
I have from my research what I believe to be a 1985 Evinrude 235 motor with 2.6 XP / GT Heads.
Block : (on freeze plug) 396045
Carbs: 395465
Power Pack: 582510
Heads: 325638 / 325639
Gearcase: 330259
The color of the motor looks like factory metallic blue.:
Compression is right around 115 with one cylinder as high as 120 and one as low as 106
I have the motor set up for premix 50:1 using Evinrude outboard oil running about 5 PSI fuel pressure off an electric pump.
From my notes when I worked on it a few years ago I wrote that it might have Wiseco pistons because of deep oil grooves, and it has 2 stage composite Boyesen reed valves.
I wrote that it has square ports also.
I run a nose cone low water pickup on the lower and at 3000 RPM it will produce about 10 PSI water pressure (on my gauge) from the water pump while also having a good telltale stream.
What do you think I can check before having to take it in?
Thanks, John

[Joe Reeves]

The fact that the problem does straighten out eventually eliminates the carburetors as they do not come and go. It they act up once, they stay that way.

Check that the timer base under the flywheel isn't sticking.

On your next outing, pump the fuel primer bulb up hard before starting the engine to see if a full fuel system eliminates the problem (failing pump?).

There should be a anti siphon valve located where the fuel line connects to the tank. If jammed open or missing... or if there but someone has removed the internal parts, the fuel can siphon back into the tank.

[hotrodjohn71]

Hi Joe, Thank you so much for your reply. I appreciate you taking my problem into consideration. I don't have a primer bulb but I have a Carter electric fuel pump I turn on before starting my boat. I have a little fuel pressure gauge and the fuel pressure goes straight up to between 5 and 6 Psi instantly after turning on the pump.
I was thinking the same thing that it might not be a fuel issue but a spark issue. Later today I can remove the flywheel and inspect the spark advance. John

[Joe Reeves]

With the engine NOT running (Safety First), you can observe that timer base easily without removing the flywheel.... just have someone slowly move the throttle while you observe the turning action of the timer base.

Just in case...... The flywheel nut torque is 145 foot pounds.

[hotrodjohn71]

Hi Joe,
I had my partner help on the throttle as I observed the advance. It tracked back and forth just fine. I physically tested its travel with my hand and it went back and forth. It didnt snap back like a rubber band, but did go full travel.

[NRGNUKE]

could you maybe test to see if you are getting spark through the range, especially at wot?

[hotrodjohn71]

Hi NRG,
That sounds like a good idea. How do I go about doing that?
Do I just remove the plugs and ground them to see spark, then while cranking (with starter), push the throttle to WOT causing it to go into full advance and check for spark?
John

[hotrodjohn71]

My apologies as its been almost 1 year since I posted this question and I haven't made a move on this issue since. Our Folsom Lake is full and I'm ready to get back to trying to solve this issue. Considering the advice that the fuel supply is not probably the issue and looking into the ignition issue and ignition functioning throughout the whole advance curve, I have a new question. I have a big plastic bin I can idle the motor in while in neutral which is great for running the motor at idle. As soon as I shift into gear, it blasts all the water out. Not having access to a test tank, would removing the prop and running it in the test tank in gear to check the ignition system through the advance curve with the load of turning the gearcase be of any advantage?

[Joe Reeves]

No... DO NOT remove the propeller and apply throttle as the engine will over-rev and possibly become a runaway engine.

In re-reading over everything, it is very possible that the high speed jets, that are located horizontally in the bottom center of the float chambers, are partially fouled, allowing enough fuel to pa$$ through for that 3000 rpm scenario you mention... BUT... not allowing the full flow for the higher rpm which results in the engine bogging down.

Two HS jets to a carburetor, one on each side in back of the drain screws. Clean carefully with a piece of single strand steel wire. Let us know what you find.

[hotrodjohn71]

Hi Joe, thank you. I was think of going through the catbs too. I will remove, inspect and clean them and go from there. Thank you.