Lazy Cylinder on Yamaha 150?

jasonalden · #1 July 11th, 2004, 09:33 AM

I have a 1997 Yamaha 150 Saltwater Series model S150TXRV with 275hours. On a usual day I get about 4800RPM at WOT. Usually it is a good running engine.

On our last outting I noticed the following happen several times:

After the engine has been off for 45 minutes or more, I would start it up and run for about 2 minutes at fast idle while I pull the anchor. Then at any RPM up to about 3000 I noticed a rough running engine. Seems like it is missing. After about 3000 RPM I feel a slight jolt and the roughness goes away and all is well thereafter at ANY RPM while the engine is running. If I shut it off for 45 minutes again, the engine runs rough again until I get it past about 3000 RPMs again.

Seems like I have a "lazy cylinder".

What would cause this? I am a first time outboard owner and not sure what to look for. Spark plugs (should I pull them and clean them OR replace them)? Fuel filter? How about carb adjustments (not even sure if I have a carb)?

Thanks!

Jason

SW Florida

http://thealdens.org/boat

jrod8v92ti · #2 July 11th, 2004, 01:22 PM

voltage leak on ignition coils or corrosion in the right place could do it. get a yamaha service manual and a meter and start looking its not that hard. about 1 sixpac you'll have the ignition figured out.

jasonalden · #3 July 13th, 2004, 09:59 AM

Thanks for your post...when you say corrosion in the right place are you saying corrosion somewhere on the ignition system, or somewhere other than this igntion system altogether?

This engine looks very very clean & shiny, except for this: Along some of the seals on the engine are showing pencil line-width rust/corrosion, as well as on 2 of the bolts that hold the engine together. You can pick the stuff off with your fingernail.

Other than that, no visible corrosion on the assembled engine.

jasonalden · #4 July 13th, 2004, 10:00 AM

Thanks for your post...when you say corrosion in the right place are you saying corrosion somewhere on the ignition system, or somewhere other than this igntion system altogether?

This engine looks very very clean & shiny, except for this: Along some of the seals on the engine are showing pencil line-width rust/corrosion, as well as on 2 of the bolts that hold the engine together. You can pick the stuff off with your fingernail.

Other than that, no visible corrosion on the assembled engine.

jim dozier · #5 July 13th, 2004, 10:51 AM

Start with a spark tester (inexpensive at an autoparts store) and a new (don't clean them) set of the proper spark plugs. Then do what jrod above suggests. When you get this fixed you might want to investigate a new prop. Generally, you should be able to reach the upper range of the engine rpm which would be ~5500rpm. You may also be due for a engine decarb (see FAQ). It may be nothing more than carbon on the spark plugs from lugging the engine.

rodbolt · #6 July 13th, 2004, 03:06 PM

at 4800 your almost 1000 rpm short of a good running rig. also check the fuel pumps and clean the carbs. the ign system on that engine is about as close to bullet proof as was ever built.

methodical testing with a test wheel and the proper equipment will show the problem quickly.

good luck and keep posting

jasonalden · #7 July 19th, 2004, 04:50 PM

We were out again this weekend and the problem is getting more obvious (worse).

Now it seems at any RPM under about 3200 the engine runs rough. Only when I bring it above 3200 does the engine run smooth.

Also, not being an outboard owner before, not sure if I am doing something right and this may have an affect on the diagnosis of my problem:

If the engine starts without ever pumping the fuel bulb on the fuel line, do I ever really need to pump the fuel bulb? I have been NOT pumping the fuel bulb usually. However, when I did pump it 6 or 8 times, it appeared that the the engine ran good under 3200RPM. This tells me maybe there is a fuel starvation problem? Could this logic be correct?

Also, ran the 52 gallon fuel tank very low last outting, and this is when I noticed this problem at it's worst. Could I be picking up water or debris on the bottom of the fuel tank OR possibly getting bursts of air instead of fuel in the fuel line and that is what causes the rough operation at times?

I picked up a Kastar Spark Plug Firing Indicator (#92A) today and will give that a try soon. Seems to me that this instrument will need a trained eye to interpret.

Thinking about pulling the plugs to inspect them too.

Thanks so far for all of your suggestions!

jasonalden · #8 July 19th, 2004, 04:57 PM

Oh yeah...Rodbolt, how and with what do I clean the carbs & how do I check the fuel pumps?

Thanks!

jasonalden · #9 July 19th, 2004, 07:01 PM

OK did 2 things tonight:

1) Attempted to make use of the Kastar plug firing tool and the piece of junk fell apart in my hands. Taped it together and it acted very seemingly strange when used it on my Oldsmobile (which runs good!).

2) I took apart fuel filter and observed a seemingly clean screen. The screen appears to be offwhite in color. There were some very tiny particles in the bottom of the fuel filter screw-on container. It doesn't seem like I have a fuel filter issue. I didn't bother cleaning it (don't quite know how and it didn't seem that dirty anyway).

That's all for now.

rodbolt · #10 July 19th, 2004, 07:53 PM

for the carbs its a matter of buying the kits and removing disasembling and cleaning. I use CRC 06064 spray and air.

on the pumps every 3 years I replace them.

regardless of hours.

its a rubber thing. if your time is worth nothing the rebuild kits are about 20 dollars and the pump is 35 or so. at 75 per hour its cheaper for my customers for me to install a new set. if you can pump the bulb and make it run better it may be a pump issue. have you noticed a more than normal amount of oil puddles on the water at idle?

good luck and keep posting

jasonalden · #11 July 21st, 2004, 08:05 PM

I did 2 things tonight: Quick cleaning of carbs, and changed the spark plugs.

CLEANING OF THE CARBS

I pulled the air filter off (and by the way it really does not seem to "filter" because there is no filter - this is strange to me.). I picked up a can of Super Tech Carburetor Cleaner and sprayed the carbs, choke plate... then started the engine and sprayed in the neck of the carbs, just beyond the choke plates. I noticed that when I sprayed in the upper 2 carbs, the engine would really almost go into a stall. The middle too (but not quite as affected as the top). But spraying into the bottom almost had no effect on the engine.

I'd have to say the carbs looked very clean as they were. No change before or after.

CHANGING OF THE SPARK PLUGS

4 of the old plugs have dark brown sticky stuff like varnish (very thin layer all over the end of the plug).

Now for the 2 other plugs (starboard center, and starboard lower), they had the brown sticky stuff too, but also some build up around the edge across from the center, and a hint of pale green substance.

Before I put the new plugs in I sprayed the holes with carb cleaner for 2 seconds each.

Now get this: Put the new plugs in, and ran the motor for 5 minutes. Then I pulled all starboard plugs out to observe. Starboard top had some brown liquid on it such as "liquid varnish" (to me it seems normal). However, the other 2 plugs had a pale or milky green substance on them, and no brown.

It seems to me that these 2 cylinders did not fire during my 5 minute run. Does this sound like a logical conclusion?

Took the boat out for a test run:

No change in performance. It still runs rough when slowly accelerating up to 3000 RPM or so. From dead stop I took it to WOT and it gave me all the power it was meant to give...no hesitation or rough operation...It just got up and went. But run it for a while at 3000 or less and it starts to run rough.

But with just me and my daughter aboard, was able to get 5000 RPM out of it at WOT and up to speed.

But in neutral, I don't get the shake. I only get the shake under load.

I did not think to pump the fuel bulb while the shake was happening to see if the shake would stop, but will try that experiment next time.

So what next? Spark or Fuel?

THANKS SO FAR YOUALL!!

rodbolt · #12 July 22nd, 2004, 03:52 AM

you cannot clean the carbs from the outside.

you must remove and dissasemble them. also if the fuel pump is over 3 years old just replace it.

why would you need an air filter ? if your boating conditions are that dusty you may need to check your depth finder.

that box is just an air silencer and it collects puddled fuel that is blown from the carbs. that motor should turn up to 5500.

test all the spark plug caps with an ohmeter.

good luck and keep posting

jasonalden · #13 July 22nd, 2004, 01:41 PM

Thanks so much Rodbolt. You have a good point about the air filter lol.

OK so the local Yamaha dealer quoted $35 per fuel pump. He said I will spend more $ trying to gather all the necessary parts to rebuild the pump. Also $50 for repair manual. Don't want to spend more than I have to so if you know if a cheaper quality fuel pump supplier (and manual supplier) please let me know.

OK sorry for the ignorance but not sure what testing the spark plug caps means? I do have a digital ohmeter though.

Thank you.

rodbolt · #14 July 22nd, 2004, 05:11 PM

if your spark plug caps are red they will unscrew from the plug lead. then use an ometer to test from the cap tip to the thread point. it should be around 5 k. I think its like 4k to 6 k ohms.

good luck and nope yamaha is the only supplier of pumps.,

jasonalden · #15 July 22nd, 2004, 06:20 PM

Just checked. They are orange. I tried to unscrew them but they wouldn't.

So I ran the engine with the cap off the plug head, and a piece of metal from the cap contact to near the plug head and I received spark on all 3 starboard plugs through a range of rpms from idle to 3000. So it appears spark is not the problem (but I am no expert here - not by any means).

Also ran the engine with both the starboard lower & center wires OFF THE PLUGS and the motor idled just the same as it did before. I pull the top one off and it really didn't idle well. So top starboard is strong but getting nothing from center or lower. Seems I am running on 4 of 6 cylinders.

Ran the engine and pumped the bulb repeatedly and hard at varying rpms and really the pumping made no difference in engine speed, or sound. I am contemplating whether I should replace the fuel pumps for $70 when pumping the bulb does not seem to help (grrrr not sure what to do).

All tests were done in neutral tonight.

Ran the engine and just couldn't keep a stable rpm above 1500. No matter where I put the throttle it would go up, down, higher , down...whatever.

Starting to wonder.

The boat has been stored in the water with engine tilted all the way up possibly for years before I purchased it last month. I wonder if it is possible that either salt water or flush water has always been sitting in the bottom part of the engine, where my "lazy cylinders" are. OR, hopefully maybe Yamaha designed the engine to drain properly (even in that full up position).

I'm full of theory but I just can't help it. I bought a used boat with no warranty and a month later here I am not sure what the heck the deal is (and it was not cheap either).

Guess I will get those fuel pumps...and a repair manual and hope it was a well spent $120.

Before I do that maybe tomorrow I'll pull a fuel line off the lower carb and see if there is good flow. Not sure what to compare it against.

Could it be possible that a fuel pump can disintegrate and pieces get stuck downstream in fuel lines, or carb?

jasonalden · #16 July 22nd, 2004, 07:10 PM

OK I will also look at getting a carb kit for a disassembly type of cleaning...as opposed to the spray-and-dash I did last night. And I will track down some of that CRC 06064 you use Rodbolt.

thanks...

jasonalden · #17 July 22nd, 2004, 08:03 PM

As I read along other posts, I see some performing a rebuild to their carb. Is this what I would be doing if I purchased a carb kit, or do I need additional parts to do a rebuild?

http://www.iboats.com/cgi-bin/ubb/ul...;f=30;t=003792

phatmanmike · #18 July 22nd, 2004, 08:43 PM

jason, where are you at in florida, i am in clearwater and can help you GREATLY if you are close enough by....

yes you would technically be REBUILDING your own carbs. its very , very simple...nothing in there but a few gaskets and a needle/seat combo... basic

you can get a manual here at iboats.com for under 30 bucks, but they are after market and cover a range of motors, for 50 you can get the one from the dealer, that is MODEL specific to your perticular motor.

by the way, how long have you had this motor and what maintenence have you done yourself so far?

mikey

jasonalden · #19 July 23rd, 2004, 07:02 AM

Mikey,

Thanks for your post. I am in Cape Coral. I purchased the boat in June with 245 hours. I was told that it had a the hundred hour maintenance done on it and was told that was water pump and gear lube.

I now have 289 hours on it and changed the spark plugs, confirmed I have spark, checked the fuel filter (pretty clean) sprayed the intakes of the carbs with carb cleaner. That's about it.

I just rcvd a price on carb rebuild kit from local dealer - $44. Thinking about buying carb rebuild kit, 2 fuel pumps ($35 each), and Yamaha manual ($50).

The problem is I have to order the manual...may take days. I would really like to do the above work tomorrow (Saturday) but not sure if I can wing it WITHOUT a manual. What do you think? I have never owned an outboard before.

Thanks again for your reply.

rodbolt · #20 July 23rd, 2004, 04:18 PM

try the local library

jasonalden · #21 July 23rd, 2004, 06:31 PM

great idea!

I found this online at the local libray (closest match):

Seloc Suzuki outboards : 1988-99 repair manual : 2-225 horsepower, 1-4 cylinder /

But I have a Yamaha..

I wonder if it would be close...hummmm. may have to give it a try...

jasonalden · #22 July 24th, 2004, 09:12 AM

I just replaced the fuel pumps: No change in idle or < 3000RPM behavior at the dock. Will test down the river in a little while.

Did notice one thing I did not point out before: I have 3 carbs and on my top one, there is a strong suction. The middle carb has medium suction. The bottom carb has very little suction. Not sure what all this means. Seems like they should all have equal suction.

I found a repair book [thanks for the library idea RODBOLT] up to year 88 [9 years older than MY engine] and I would have to say that rebuilding the carb looks VERY intimidating [let alone rebuilding 3 of them]...and then having to sync the carbs to the ignition....ugggggg. If the actual procedure for my 97 is anything like the 88, then that stinks!

I purchased 3 carb rebuild kits [$45 X 3].

Dealer wants $300 parts & labor for clean & rebuild of all 3 carbs. He said I will burn up the engine if I don't sync it properly. May spend the $300 but still not sure if DIRTY CARBS are the problem????

Hope ya'll are having a good weekend.

jasonalden · #23 July 24th, 2004, 12:51 PM

Just took it out for a test run. It still runs rough up to 3000RPM. Ran at WOT (5000RPM) for a minute or two and then engine ran smooth from idle to WOT, thereafter. It was only after I shut the engine off for 10 minutes or more does it run rough under 3000RPM.

Next, I purchased and put in the fuel tank:

3-12oz Super Tech Fuel Injector & Carburetor Cleaner 074509733578.

1-12oz Super Tech Gas Treatment 074509733615.

I wonder if I should disconnect the lower carb fuel intake line and put some compressed air through it.