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Gas/oil residue on '1996 Evinrude 90hp

otis

otis

Member
Inside the engine cowling, the port side of my motor is lightly covered with what seems to be a gas/oil mixture blow-by. Engine runs good but is hard to start. Starts instantly after initial start of the day.

Any ideas why there is residue on one side of the powerhead?
 
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Re: Gas/oil residue on '96 Evinrude 90hp

Those motors generally start instantly, you may be doing something wrong.----------------Outline exactly how you try and start it , maybe we can give some tips for instant starting.---------------------If you tilt the motor with fuel in the carburetors it may leak out, gas evaporates and oil stays behind. ---------------------Also start motor and look for leaks on all hoses.
 
Re: Gas/oil residue on '96 Evinrude 90hp

First I would say that priming the bulb is a guestimate most times. Sometimes it is firm after a couple of squeezes, on other occasions it takes 6-7 times. I feel I may be flooding it because of this.

I push the key in to choke while turning the key to start. I do not give it any throttle or pump the throttle while trying to start. Many times the starter will disengage quickly after initially turning over. I repeat many times until eventually it will putter and start then I baby the throttle until I can get some revving to warm up the motor. ALL other starts the rest of the day are instantaneous with a key bump. Motor runs good thereafter.

Top speed is around 40 mph at 4300-4500 rpm on a small 15' 8" Stratos 258V.

Thank you.
 
Re: Gas/oil residue on '96 Evinrude 90hp

The bulb on the hose is wrongly called a " primer bulb ", It only fills the carburetors and saves the starter doing that.-----------It is nothing but a " manual fuel pump "------------So pump the bulb till it goes firm.-----------------If it does not go firm find out why.----------------------Operate the throttle only lever! to gives some throttle in nuetral, full up will give quicker starts ! a must for a cold engine ---------------Crank it over while key is pushed in.-------------Push in key as required till motor warms a bit.-----------------------Do not let the motor wind up beyond 2000 RPM in nuetral.--------Hope this helps.
 
Re: Gas/oil residue on '96 Evinrude 90hp

Thanks for the help racerone. My boat has a "hot foot" throttle as opposed to a throttle only lever. Should I fully depress the hotfoot pedal while trying to start?

I rev carefully while in neutral. Just enough to get the cold engine running.
 
Re: Gas/oil residue on '96 Evinrude 90hp

I am not sure of the hot foot throttle. Do you have a seperate unit for the shift function?----------------If so you must give this motor throttle for cold starts.-------------Do not give it throttle so that it winds up to over 6000 RPM in nuetral ( bad , bad for an outboard )----------You should experiment with the amount of throttle for cold starts.-----------------Should start effortlessly if done the right way.
 
Re: Gas/oil residue on '96 Evinrude 90hp

There is a shift gear, but it has no idle throttle lever. I will experiment with the hot foot to see if I can find the right spot for quicker starts. Thank you for the information.
 
Re: Gas/oil residue on '96 Evinrude 90hp

4500 rpm WOT I would suggest you are also over proped and lugging the motor and risk fouling the plugs.
 
Re: Gas/oil residue on '96 Evinrude 90hp

@Cliff, I will recheck those numbers this weekend for accuracy. What should the correct rpm's and speed be at WOT?

Any ideas what is causing the oil/gas residue inside the cowling?

Thank you.
 
Re: Gas/oil residue on '96 Evinrude 90hp

the residue (imo) is a result of starting hard a little gas / oil mix spays out of the carbs., evaporates and leaves the oily left overs.
5000 to 5500 is a good range for it to run. but hopefully some one with can elaborate on this!
 
Re: Gas/oil residue on '96 Evinrude 90hp

Any gas oil mix that sprays out of the carburetors is looked after by the drain / hose to the intake manifold and this does not make a mess inside the cowling !!!
 
Re: Gas/oil residue on '96 Evinrude 90hp

Perhaps the residue happened in the past and is not recurring. What would be a safe way to clean it off? Can I spray the powerhead with water?
 
Re: Gas/oil residue on '96 Evinrude 90hp

Spraying with a cleaner and then water is OK----------------------------------------------DO NOT LET ANY WATER FIND IT"S WAY INTO THE ENGINE !!!!!!---------------Spray with " CASTROL SUPERCLEAN " on a warm engine. Rinse with warm water. You must run engine after this to make sure no water got inside the engine !!!!!!!
 
Re: Gas/oil residue on '96 Evinrude 90hp

one more though on the residue if its not reoccurring: is one method of winterizing is to spray the fogging oil over the motor!
It could be that could you take a pic I would say keep some of the residue so maybe just wipe some out. it wouldn't hurt to make sure the drain racerone was referring to is not clogged.
 
Re: Gas/oil residue on '96 Evinrude 90hp

@Cliff: This past weekend WOT was 4500 rpm and 40 mph. Water was rippled but not choppy and the boat was well trimmed and running on the pad. Do you feel this is not enough rpm or mph or both? I have not been able to find any identifying information on the prop, but it is stainless steel, 3 blade.

I have a hydrofoil on the motor which causes the boat to pop on plane very quickly and/or the prop was chosen for hole shot rather than speed.

Is there an easy way for me to determine prop pitch? What prop size and pitch should I be running on a 15' 8" (258) 1996 Stratos with a 90 hp two stroke Evinrude?

I will decarb in another month or so and install new plugs. Hoping this will increase the rpm and overall performance.
 
Re: Gas/oil residue on '96 Evinrude 90hp

Well I would not worry about the speed just the RPM's.
According to my prop. calculator I am going to say you have a 21 pitch prop. you may want to try a 19 degree prop that should bring you up 400 RPM's and you motor should not labor so much. you speed how ever will remain about the same.
 
Re: Gas/oil residue on '96 Evinrude 90hp

Otis,
Did you buy this boat with the HotFoot installed by a previous owner? A common performance upgrade for 'hot shot' bass boats is fiberglass/carbon fiber reeds in place of the OEM metal reeds. I'm going out on a limb here, but I would bet the previous owner installed performance reeds in addition to the HotFoot pedal. The performance reeds can help with better air flow, throttle response, and top end. The problem is the thin material in these makes them prone to chipping and/or breaking. I've done a lot of work with PWC's which use these kinds of reeds and this is a fairly common problem.

Hard starting and 'blow by' (oil mist) coming back out of the carbs is a tell-tale sign of a bad reed petal(s). I suggest you remove the front of the flame arrestor so you can see the carb throats. Now, start the engine on a hose and muffs (or at the dock) and observe each carb and look for a fine mist coming back out. You might need to run the engine at high idle to get the butterflies open a bit to make the mist visible. Another option is to hit the lake with the motor cover off and flame arrrestor removed and observe the carbs while someone else drives the boat. In a worst case you may need to remove the reed block and inspect them visually.

The low max RPM can be cause by air escaping the cylinders during the compression stroke resulting in reduced 'charge' and less power when the spark plug fires.

Kevin
 
Kevin,

This boat was purchased with the hot foot already installed. This weekend I will check and test as you have indicated. At what RPM do you consider a high idle?

If faulty, are the reeds something that I can install or should it be left to a professional?

Thank you for your input.
 
If that engine is equipped with the "Fast Start" feature, and I think it is, there would be no need to apply throttle in the start mode. If not, inform me and I'll stand corrected.

On a flushette, the normal idle rpm would be 1000 rpm (20" shaft eng) or 1200 rpm (25" shaft eng). The idle rpm in the water would drop to a normal rpm.

What are the compression readings of all cylinders?

With the spark plugs removed, the spark should jump a 7/16" gap with a strong blue lightning like flame... a real SNAP! Does it? Note that the gap is important... checking spark by using the spark plugs is a waste of time.

Possibility that the engine is cranking over slow when cold which could result in weak erratic spark, then when warm the cranking rpm is higher resulting in a proper spark. Something to consider. The engine needs to crank over approximately 300 rpms in order to properly engage the ignition (spark).
 
otis said:
Kevin,

This boat was purchased with the hot foot already installed. This weekend I will check and test as you have indicated. At what RPM do you consider a high idle?

If faulty, are the reeds something that I can install or should it be left to a professional?
Click to expand...

Maybe 2000RPM for high idle.

Reeds aren't too hard to replace. It's time consuming if you're unfamiliar but not impossible. With the Flame arrestor off you should be able to easily tell if you have a bad reed. Mist spraying at you or a chuffing sound will be dead giveaways.

I look forward to hearing if this is your problem.

KJ
 
Checked the spark plugs and found them to be gapped incorrectly. They were all .025 rather than the suggested .030. After correcting this, starting was much better. Still sluggish while cold, but much better than before.

Also gained about 300 rpm in WOT and about 3 mph.

I did not get around to checking the reeds. Hopefully I will have time this weekend.
 
Check the compression while you're at it. I may stand corrected here, but I believe a cylinder with bad reeds will also have lower compression. If the air charge is able to escape back through the carb you'll have less air volume to be compressed and will result in a lower reading. Again, this might not be quite right but I believe I read this at one time.

Also, those low WOT RPM could be a result of reduced power from bad reeds.

KJ
 
Reed valves have nothing to do with cylinder compression !!-----------In fact when cylinder compression is happening the reed valves should be OPEN.-----------------Reed valves have to to with crankcase induction and CRANKCASE compression.-----------------A 2 stroke engine is a 2 stage air processing machine.
 
When the piston is on the down stroke the reeds should be closed causing the air/fuel charge to be pushed through the transfer ports into the cylinder. That is point where a bad reed comes into play because some of the air escapes back out of the carb instead of entering the cylinder. I understand the reeds will open as the piston passes in the intake ports and creates a vacuum in the crankcase. I just couldn't remember exactly if reduced amount of air charge effected compression.

Regardless if a compression is effected I'm certain that a broken reed will cause a reduction in power. Less energy in means less power out.

KJ
 
The reeds open when crankcase volume increases ( piston going up in the cylinder ) and closing off the intake ports , pulling a fresh charge of clean air and fuel into the crankcase.. Then compression in the cylinder starts.--------------Reeds close when piston is coming down in the cylinder ( power stroke ) and crankcase pressure increases till the piston opens the intake ports.--------------------The amount of crankcase compression determines how efficiently the cylinder is scavenged.-------------Reeds on the Johnson / Evinrude V-4 motors rarely fail.
 
racerone said:
Reeds on the Johnson / Evinrude V-4 motors rarely fail.
Click to expand...
Agreed. The OEM reeds are extremely durable. The OEM reeds on my '79 Evinrude 140 are in fantastic condition and I have no doubt they'll last indefinitely. The only reason I suggested the OP investigate integrity of the reeds is because many in the go-fast crowd are convinced that non-metallic reeds are a necessary upgrade for a performance bass boat. The existence of the Hot-Foot throttle and the symptoms described by the OP made me wonder if someone possibly installed aftermarket reeds in this engine as a performance upgrade and that one or more petals is failing.

What I am suggesting is a simple test that should take less than 30 minutes to complete. If there's a mist shooting out then bingo, the OP has quite likely solved his problem. If it all looks good, then he continues down the process of elimination and can check that one off the list. That's all.

KJ
 
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