decarb

[smokepoles]

What are your thoughts on the 'necessity' to decarb an outboard? I am contemplating for the 1990 Evinrude 90 hp that I purchased recently as soon as it gets back from the shop. I'm having them go over everything so that I know where it is at, and can go from there.

It was idling poor and stalling when put into gear unless you gunned through it. Not good choice at the dock or loading. First question mechanic asked is did you put 85 into it? I had, not knowing better, as I do with my lawnmower, chain saw, and weed wacker. So, we will see if that takes care of the idling/stall issue.

It runs great at all other rpms, and put about 60 mi on it last weekend fishing at Strawberry Res here in Utah. Lost a few hundred rpms at WOT to about 4700 rpm at the lakes elevation of 7600 feet, and might have to reprop when I fish there.

 

[SuperD]

Did all the rough running occur at Strawberry or has it been doing it all along? Carburated motors are a PITA in general but what often happens is the carb get jetted for one elevation and runs crappy at other elevations. Sometimes a small adjustment in the air / fuel screw will make it run well enough for an occassional trip to that altitude. If that is a regular fishing spot, getting the carb rejetted is usually the solution.

 

[smokepoles]

I had only recently purchased the boat, and it seemed to idle and go into gear fine the first couple times out, but it had then started stalling out around home. I can't exactly place when I first put in gas, but I am hoping it is just the 85 octane gas I have been using. We are around 4500 feet elevation at the local reservoirs, and I hope to use it at the Gorge (about 6000) and occasionally Strawberry (7600) and other area reservoirs that are within those elevations.

Another interesting thing at Strawberry was that the motor would not even turn over first thing in the morning, no click or anything. Switched batteries the first day and still nothing. Pulled it out and went back to camp. Removed cowling and checked connections, etc. All of a sudden it worked. Put back in, and started fine all day. Same thing next day, except fiddled with it at dock (mostly just looked and shook heads) until it caught and turned over. Started fine rest of day. All we could figure was that the dampness from the heavy dew every morning had shorted out something and removing the cowling let it dry out.

Ah, the joys of boating.

 

[SuperD]

The first 2 things to check when the motor won't turn is the throttle being well clicked into neutral and the key deadman clip is fully snapped in place. Regarding gas, had you completely emptied the fuel tank before running it with the new? No telling how long the previous owner had allowed the gas to sit. Go ahead and try the decarb but if some old particulate has blocked the carb, a through teardown will be required.

 

[smokepoles]

I did put it in free throttle several times and checked dead man to see if that was the problem with the early morning starts. However, you well may be right that the throttle could have been the 'short' rather than the engine because the throttle are would be very exposed to the heavy dew.

The original tank showed about half full, and that seemed to work fine for the first couple short outings. But again, you make a good case that may well have just introduced the problem. Perhaps it would have been better to top off with fresh fuel from the get go.

These are simple engines, but is amazing how complex the issues can be, especially how such a variety of causes often lead to the same problem in function of the engine.

Thanks for the input.

 

[SilverBullets]

I had issues last time out with a Yamaha 6hp 4stroke. It started up and trolled just fine but cut out/bogged down at high speed. Found out it was just the gas. Put in some fresh 92 octane non ethanol in and problem solved.

 

[SuperD]

A lot of gas nasties are heavier than the gas and sit on the bottom of the tank. This is coincidently where the fuel pick up tube sits. Even if you had topped off, it would have likely pick up some crud. I've gotten in the practice of completely draining my tank every couple of years and using the gas in my lawn mower and old beater commute car. Those systems are a lot less finicky than marine outboard motors with a carburator.

 

[smokepoles]

Update

Still do not have boat back. Mechanic said the water pumps were pretty much toast on both motors. I had watched both carefully that they were always 'peeing' strongly, but guess I was lucky they did not go out. Just reinforces to have them and other things checked on used motor even if they run well when looked at.

Anyway, with increased pressure from new pumps, they noted an leak in the exhaust and I said to go ahead and replace gaskets. They told me today that water was indeed leaking into pistons, and I hope that the new gaskets take care of that and solve the poor idle. My thoughts are that a piston may well have been dropping out at idle and stalling it out when going into gear, but running well at higher rpms where a bit of water would be overcome.

SuperD, you'll have to come out and fish the Gorge with me if I ever get the boat in shape to take others out - I don't mind stranding myself as much as some one else.

Time for this Wisconsin boy to watch the Packers! Go Badgers!

 

[Ryno]

Smokepoles,

My last boat had a carbed Mercury 125HP. When I first got it, it had been in storage for about 1.5 years. It started and ran fine, with exception to being sluggish at idle and top end. I emptied the tank and refilled, running a bottle of fuel treatment through it. Not much change. I bought a bottle of Mercury Powertune and treated the motor and the results were unreal. My top end went from about 4600 RPMS and 33 mph to 5200 RPMS (max) and 38 mph. It also started easier and ran great across the entire power curve. After that, I treated it once a year using Powertune always noticing a difference. I also spoke about the results with a mechanic in SLC. He indicated that anytime he gets an engine his shop with potential carb issues, it's the first thing he tries and a lot of times it's the resolution. Might be something worth trying, and for $10-15 a can, it's not to much investment either.

Good luck, Ryno

 

[smokin' Kokes]

decarbing is mandatory on 2 strokes because of the extra carbon and other combustions produces build up in the combustion chamber, piston crowns, crank case, scavenging exhaust and especially the rings/piston ring grooves. Manufs. even have a name for carbon ring build up, ring jacking. rings are forced out against the cylinder walls excessively and no longer flex properly, causes excessive cyl wear and lost HP.

I mix my own decarb compound out of the same ingredients used in the OB manufs concoctions. Mix of 80% paint store acetone, 15% xylene, 2% MEK and 3% TC-W3 OB oil
low cost and effective. use spray bottle and shoot in thru the carbs. until the black crud pours out the exhausts.
as Ryno noted, really adds to engine performance increase especially the first time.
also add some of the mix to every tank of non ethanol gas. ounce per gal.

also douch the 4 stroke kicker, about the same way, carb spray couple times a year and in the gas tank.

if the black crud blown out is thick and large amounts, plan on 4 stroke oil change immediately after. first time i did my kicker, oil was like a tar pit after

 

[smokepoles]

After they replaced the exhaust gaskets, they put it in tank and said it was now idling too fast and could not get it down any lower because the cable would not allow. Checked at throttle/shift lever and mechanic concluded the cable must be stretched in middle (not sure how that happens). So, I had them replace cable with one they had on hand.

At the same time, the mechanic said that there was problem with tilt/trim in that motor did not stay up. I had not noted any problem nor seen any signs of leakage before buying or using, but then again the other problems I am dealing with were not evident either. Mechanic thought it might need new seals in tilt cylinder, and daid he would look in what it would take to fix - new seals, whether need to remove motor to work on or not, etc. Had me worried that I would need to invest more in getting this going.

Mechanic called today and said he looked over everything, checked oil, etc, and couldn't find anything. Even stayed way past regular hours looking because he couldn't pin down a problem. Turns out another mechanic had lowered the motor while mine was away for a few minutes. So, bottom line is it is OK (for now anyway).

I am finally due to get my boat back today with everything seemingly running right. I'll ask what carbon build up was like when they had the exhaust off. I know thy could see where the water was leaking in. Then I'll run it for a base line before any decarb so I can judge effect.

 

[smokepoles]

what a joy!

Thanks to those whop have followed and replied to this saga.

I took the boat out this afternoon/evening to the local reservoir, and motor performed great! It started right up, idled at reasonable rpm, shifted into gear and didn't bog down..... Boy, that makes docking and loading a lot more fun. So, I can confidently say that water leaking from exhaust into three cylinders is not good for outboard performance.

I had my son and family out tonight, so we decided to leave the decarb for next time. My mechanic said is was not bad, but that a decarb would not hurt. While not cheap, it so nice to have good marine service two miles down road, especially when I know people drive 90 miles from Salt lake to take their boats there.

And on a continuing positive note is that the boat did again not leak a drop of water from drain when we took out. So maybe this used boat purchase will work out.

As to the fishing, we boated 15 or so rainbow and the grandson had a blast!