Outboard bogging down. Take a look, tell me what you think.

Nick,where did you learn to be an outboard mechanic?? lol !!!
someone must of done ya good.

Some random pilot dude. Still owe that guy a drink or two…..

MNdrifter wrote:

They are BUHW-2’s. Sheldon confirmed these are the right plugs to be using via PM.

OK, good. I didn’t do a lot of work on my dad’s Merc 40 but I’m sure I must have at one point changed plugs. I didn’t recall that surface gap plug, but there you go.

I’m just always on the lookout for guys trying to use weird stuff on outboards and small engines that sounds (to them) to be better and more reliable. The current fad is to run diesel motor oil in gasoline engines.

Grouse

Thanks again Sheldon and guys for the help! Put new plugs in, and she ran like a new top. All that worry for nothing. Fishing wasn’t bad either! SW Wright County lake, pulling slow death and crawlers on bottom bouncers. Also slip bobbers and leaches. Hope to get back there Sunday, weather permitting.

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nice job drifter !!!
now,even though thats a smaller motor on the hp scale these days it still needs run,and run often,dont be afraid to crank it up a few times a day to clean it out.

who knows,the previous owner may have babied it way too much,something two strokes dont like as they need cleaned out so that they arent loaded up.
the plugs need the heat from high speed runs to keep from fouling as well as burn off any carbon deposits.

the worst thing on any motor is to sit ,they will give less trouble ran every day than they will laying around.
one more note,that motor isnt made to run above fifty seven hundred rpms at wide open throttle non stop,make sure you are propped right for that.

edit to add: nice fish and glad you had a good day on the water!

Not to be a negative nancy but my concern is that you fixed a symptom, not the problem. Why are plugs going bad?

That sudden stutter miss at high rpm is generally not a plug problem alone. Were it a plug problem alone, you would have hard starting and poor performance from idle all the way up the RPM range.

My guess is weak coil causing incomplete combustion and therefore the early death of plugs. I’m suspicious that the plug stockpile you found from the previous owner is telling us that plugs aren’t the root cause and that he was also putting a band-aid on the issue.

FWIW, my father had that exact motor in a 1990 version and since I do all his outboard work, if it was a plug eater, I’d remember. If I changed plugs in the 10 years he owned that rig, it was once.

I recall, however, that it did need a new coil at some point.

Sheldon waddya think of that theory?

Grouse

Been at a couple stores and shops myself where I see clerk’s/stock boys putting away plugs and they drop one.

Always wondered how many times that happens and how many plugs go out off the bat or prematurely.

Personally I like grouse thinking, but that’s something I throw on the brain pegboard. It’s there but not a concern. Carry extra plugs and symptoms show again and it’s same plug now you got a pattern.

I tend to overthink mechanical stuff way too often and it has bitten hard back at times though.

Grouse,I agree with you for the most part,if the problem shows up again we know we have a problem,but,
if you look at the plugs in his picture they are glazed over which tells me it was idled too often and for too long as well as run too cool ( idling )

if two or three of the plugs were chocolate brown in color and one or two was glazed then we would know that one or a pair of cylinders were not firing properly.
this can be a result of any of the following,low quality oil,poor spark at any rpm,low compression,carb over fueling,etc.

if I know anything about the two stroke mercs,they dont like trolling or idling for extended periods,they need the snit run out of them often enough to keep the plugs cleaned off and the crankcase/intake and exhaust ports cleaned out.

when you idle or troll for a long time,oil will settle out and lay in low places as well as cling to the under sides of the pistons and crank throws.
when you accelerate the oil gets thrown back into the air/fuel stream and the first place this oil lands is on a hot spark plug fouling it.
if caught quick enough it will burn off and pass through into the exhaust stream with no harm done,but keep it up and see what happens.

remember,this motor is oil injected,not blended,the oil is injected at the base of the carbs where it meets the air/fuel stream,at low rpms it will tend to puddle like I mentioned.
add to that the bottom two cylinders tend to run a bit cooler than the top two at low rpms.

at idle,the oil ratio can be anywhere from 80 to 100 to 1 if the pump is set up properly,at wide open it is closer to a 40 to 1 ratio.
keep in mind that oil is supposed to be blended with the incoming air/fuel charge which it will do effectively but some settling does occur under prolonged periods of low rpm use.

another way it can over oil is if the pump is not adjusted right or the 2psi valve has stuck open allowing over oiling.
excessive oil consumption would be my first clue if these two things were to happen.

I wont be surprised if he does foul a couple more plugs if that motor has a lot of prolonged trolling hours on it and it will take many high speed runs to clean it out as there will be a lot of crud laying around in the crankcase,only good fuel,oil,and a lot running will take care of this.

hope that makes sense.

One thing I did notice last night was the ball on the fuel line got rock hard and stayed hard the whole night. I never could get it to stay hard before. Sounds personal I know. Lol. But maybe it’s using less fuel now too?

most likely it is staying that way because you got away from the misfire which was causing a backfire,the fuel pump works off of crankcase pressure pulses and those pulses are cancelled out during a backfire and the bulb will never pump up.

as far as fuel consumption,when a motor is running rough it will use more fuel.
get it running efficiently and it will use less fuel.

confusing isnt it??

Hey guy’s. I boat my first boat of my life this past year. It’s a 30 year old bass boat in great shape. It has a 200 mariner 2 stroke on it that has been well maintained. I am mechanically inclined when it comes to cars but when I took the cowl off for the first time I thought I was in Frankenstein’s laboratory. Wires going everywhere and stuff I never seen before. Anyway, I’m impressed with your thought process and knowledge of these out board motors. I know now that Mariner is basically a Mercury. I had to bring it to the shop twice so far and am learning the labor part of repair’s is very expensive. Reading your post I think I might have an over oiling problem because I do a lot of idling around when crabbing and fishing. I’m getting ready to change the plugs and hope my problem goes away. The problem I’m having is when I go to mash it to get up on plane sometimes the motor starts shaking and bogging And the rpm’s won’t go up. It will idle fine and cruise around at low speeds but won’t get up on plane. It’s not consistently doing it either. Sometimes I can step on it and it gets right up on plane and runs great. Once it’s up on plane I have no problem’s at all. The stator has been replaced and all 3 carbs have been cleaned along with the primer bulb and main fuel line. I’m hoping it’s the plugs because it calls for the surface gap plugs which I am putting in but if they foul easy at extensive idling how can I avoid future problems. Any advice would be greatly appreciated.

I need your help! Go to the end of this forum to read my issue. Thanks