1985 evinrude 115 vro bogging after a perirod at WOT

[fishing again]

Ok brains, here is one for you. I have a recently purchased a 1985 Ranger 350V with a 1985 Evinrude 115 VRO so I do not have any history on the boat or motor. Here is the problem, The first time out with any length of extended run time, 8-10 minutes at 5000 + RPMS the engine started to loose power i could throttle back and the engine would pick back up, like it was starving for fuel but my glass fuel filter was full. This has happened the last 3 times I have run the engine for any extended length of time, I have a feeling it is heat related. There is a good strong stream coming from the water circulation hose on the lower cowl which I know does not prove a whole lot. Running on the muff at 2000 RPM the engine does seem to get a little hot after a few minutes so i'm thinking there is a flow problem. I am thinking rebuild the water pump, pull the heads and replace the water flow directors and the thermostats. Any and all input will be greatly appreciated. Oh one more thing, do I have to pull the power head to get to the thermostat housing I know where it is located just not sure how to go about removing it. What is the best way to get to the thermostats? Thanks

 

[jakedaawg]

Always replace the impellar on a new to you engine. Sounds like something is getting warm. I wouldn't worry about pulling the heads to replace the the rubber diverters or whatever we call them yet.

Start with a compression test before you spend money on the impeller. Spark test wont hurt either.

 

[emdsapmgr]

The telltale indicates that the impeller is pushing water up to the powerhead. It does not indicate whether the water is circulating completely through the powerhead and is being discharged back into the midsection. If either of the two thermostats is stuck shut, the powerhead will overheat and you should get a hot horn warning. If the horn is not working and the powerhead overheats, the engine can slow as the pistons expand inside the liners-not a good thing. Both stats are inside the thermostat housing, just under the back of the powerhead on the exhaust adapter. The two large hoses there connect the heads to the stat housing. On a flaback, its fairly accessible. You can see the factory parts diagram at this website: epc.brp.com

 

[Fed]

I wouldn't read anything into your glass fuel filter being full, if the tank isn't breathing properly or you have a restriction the pump won't be able to suck that fuel up.

 

[fishing again]

Thanks for the replies everyone I plan on doing a couple of test this weekend.
(1) Run the motor on the left side tank to see if I get the same results, with the location of the tank switching valve the right side has twice as far to travel. I have replaced all of the fuel lines and used new worm screw clamps.
(2) Carry a infrared thermometer and shoot both sides of the block to compare temps.
Maybe one of these test will yield some good info.

I really don't think it is a critical issue I have worked on a lot of different motors in my time including lots of two stroke motorcycles, and this does not act like it is anywhere near a seizure problem. My thoughts were that the heat could be causing some sort of an electrical component failure. When the motor acts up it has never died and seems to continue performing at lower RPMs and also seems to idle fine. I have turned the motor of after an episode and it fired right back up afterwards and ran fine.
As for the thermostat change, this motor is a hump back and looks like it will be a challenge to remove the thermostat housing as it sits, if it is doable I think i can manage. I do have a manual I downloaded but there is not much on troubleshooting.

 

[emdsapmgr]

You are correct. Heat is the enemy of an weak ignition component. The weak component can start to break down once the engine heats up to normal operating temps. Usually 143-155 at idle. Maybe 20 degrees lower, once the engine gets up on plane and the pressure relief valves open. If you find no spark on one side of the block, you can always swap to two power packs. That will tell you something. There are some great ignition troubleshooting tips at this website: cdielectronics.com. Esp for the stator and timer base. If they check out, then the power pack becomes a prime suspect.

 

[fishing again]

UPDATE: So this morning I took the boat out to go fishing running the opposite tank. First trip about 3 miles with no problems I checked the water stream and it felt warm. Second trip about 6 miles no problems. Third trip the 6 mile return after about 5 miles started to loose power, shut the motor down removed the cowl and felt the cylinders. Both sides seemed to feel the same both were pretty hot I could hold my hand on either for maybe 30 seconds or so. Put the cover back on started right up and ran 1/2 to 3/4 of a mile before it did it again, backed of to 3000-3200 RPMs and seemed to be ok the rest of the way to the launch. So now I am thinking more that it is a heat related problem. Ideas?

Just ran the motor on the muff for about 15 min, 5 min at 2500 RPM and measured the temp from a head bolt on each bank the results were left side 123 degrees and the right 119 degrees the pee stream never got warm.

 

[racerone]

You might want to report the results of a compression test.---You might want to look into the water diverters as mentioned before.

 

[Fed]

Still sounds like a fuel delivery problem to me, not sure why you're fixated on the temperature?

 

[emdsapmgr]

The temps you measured were fairly cool. Actually below "normal", but certainly not a problem. It's also possible one or both of the stats are stuck open, which will make the engine run cool. A cool-running engine is not good, long term, but is likely not the reason for your current problem. Think I'd do a fuel test next time the engine slows: constantly prime the fuel hose bulb while running. If the engine runs ok at WOT as long as you prime the fuel hose bulb, you should be looking for a fuel restriction, including a weak fuel pump.

 

[fishing again]

Well everyone that said it was a fuel delivery problem, I believe you are correct. Now after close examination of the fuel system the filter element is coated with reddish brown gunk, probably old gas. The question is can I get rid of it without pulling the tanks. I have added a bottle of seafoam to each tank and a fresh fuel filter, do I just keep doing this until there is no more gunk?

 

[emdsapmgr]

The reddish brown "gunk" is probably residue from water in the fuel system. I'd want to immediately pump the tank(s). Also, pull the float out of the tank top and look down into the tank to see what you are dealing with. If you are really lucky, you might get by with just pumping the tanks. I'd also check the oil tank to be sure there is not a layer of water at the bottom of that plastic tank, too.

 

[fishing again]

I pumped down this tank once already and found no water and there is no oil tank it has been removed and i am running premix. I guess I need to run/pump it down and pull the sender to have a look.