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yamaha 9.9

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carmelocataudella
Deckhand

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USA
10 Posts

Initially Posted - 08/12/2009 : 06:22:52

i have a 9.9 yamaha (that i thought was an evinrude - confused with the dinghy motor) that had one of the plugs fouled. it was running kinda weak. i changed the plugs and the engine still seems like its not running at full capacity, although it revs with no problem in neutral. any quick things i should look at or just live with it until i pull the boat out at the end of the season? i am on a mooring and its a huge hassle to do any kind of service on the boat from where the mooring is...
another thing i noticed is that the bottom is collecting a good amount of stuff growing on it and i wonder if that is screwing up the hull speed and making the motor work too hard to push the boat. i just got it this season (boat and motor)and i have not hauled it out yet to see the bottom so i wonder...

carmelo
84 catalina 25 fk/sr
"cyndy sue 2"
smithtown, ny

Edited by - on

mlg3733
Navigator

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118 Posts

Response Posted - 08/12/2009 : 06:45:26

Is the outboard a two of four stroke model? If a two stroke the carburator is probably gunked up and needs cleaning.

Edited by - on

Dave Bristle
Master Marine Consultant

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Djibouti
10005 Posts

Response Posted - 08/12/2009 : 07:21:02

Question #2: Yes.

Question #1: Is the plug in that cylinder fouling again? A fouled plug suggests improper combustion from low compression in that cylinder... You can do a rough compression test by removing one plug, pulling the starter cord, replacing the plug, removing the other plug, pulling the cord, and comparing the resistance. The causes of low compression vary somewhat between 2-strokes and 4-strokes...

Edited by - on

carmelocataudella
Deckhand

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USA
10 Posts

Response Posted - 08/12/2009 : 07:42:00

its a 4 stroke with electric start.
i will get to the boat to check the plugs again and post that info asap.

Edited by - on

DaveR
Master Marine Consultant

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USA
2015 Posts

Response Posted - 08/12/2009 : 08:50:51

I'm leaning heavily towards the gunky bottom. You may have a dirty carb but if the bottom's really bad it will make a motor work awful hard, and a 4 stroke doesn't have a bunch of low end tork either.

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cat25
Navigator

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USA
140 Posts

Response Posted - 08/13/2009 : 04:01:23

Do you havestablizer in the gas? If not I would put PRIG stablizer in the gas. It also cleans the fuel system. Great product have good results with it.

Edited by - on

jerlim
Master Marine Consultant

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USA
1484 Posts

Response Posted - 08/13/2009 : 08:05:24

I try to keep the bottom clean by going out as often as possible

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Tom Gauntt
Navigator

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204 Posts

Response Posted - 08/13/2009 : 08:47:06

Carmello,

You could have two problems... fouled bottom AND a motor needing a tune-up. I remember reading somewhere that a fouled bottom exponentially increases drag due to the increased surface area of all the marine growth attached to the hull. This increase in "wetted area" in effect increases the virtual surface of the hull. I would start there... have the bottom cleaned and then see what happens.

If you are fouling one plug consistently, you might have a problem with that cylinder... worn rings, burned valve, etc. Neither of these is easy or cheap to fix. A tune-up might shed some light on the condition of the powerhead. If the motor is old and/or been used a lot, it might simply be at the end of its useful life.

I'd have the bottom cleaned first and then at the end of the season take the motor in for a tune-up.

Good luck!

Edited by - on

Dick Johnson
1st Mate

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USA
40 Posts

Response Posted - 08/13/2009 : 08:47:58

The 9.9 Yamaha will go into a very slow mode when the oil pump quits working. I had to limp in. The light on the front is the indicator if there is a problem.

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carmelocataudella
Deckhand

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USA
10 Posts

Response Posted - 08/16/2009 : 06:44:48

i went to look at the motor yesterday and the plugs seem ok but the stern bottom and the rudder have a layer of crud on it that seems like a berber carpet.... holy cow.
i just bought this boat this summer and the bottom was clean when i got it but it looks like everything is sticking to it now.
does this mean that the bottom paint is done? if i have it cleaned and repainted for next season will that solve the problem?
i thought that bottom paint was supposed to not let stuff stick to it...

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mlg3733
Navigator

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118 Posts

Response Posted - 08/16/2009 : 08:15:06

You probably do need a fresh coat of paint. The warm weather does promote marine growth, which is why it is increasing rapidly as summer progresses. Make sure you power wash the bottom when you pull the boat out for the season, otherwise it will stick like glue as it dries out.

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Dave Bristle
Master Marine Consultant

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Djibouti
10005 Posts

Response Posted - 08/16/2009 : 11:48:47

<blockquote id="quote">quote:<hr height="1" noshade id="quote">Originally posted by carmelocataudella
 ...i just bought this boat this summer and the bottom was clean when i got it but it looks like everything is sticking to it now.
does this mean that the bottom paint is done?... i thought that bottom paint was supposed to not let stuff stick to it...<hr height="1" noshade id="quote"></blockquote id="quote">Depends on the "stuff". Are you seeing barnacles (which initially look like grapes), or just mossy/grassy growth? Depending on which, there are a couple of possible explanations:

1. "Hard" bottom paints ("modified epoxy") can rapidly lose their antifouling properties when the boat is out of the water, in as little as a few weeks. If the boat is stored on the hard over the winter, you'll have to put a new coat on just before launching. Eventually, you have to strip the old stuff off.

2. Ablative (copolymer) paints generally don't lose their effectiveness over the winter--thus the term "multi-season". You only need to add a coat when the last one has worn away, which could take a few years on a sailboat. Some ablatives have an additional biocide to help prevent plant growth--moss, slime, grass... Interlux's is Biolux, and Pettit's is Irgarol. I've found them to be effective and worth the premium.

Edited by - Dave Bristle on 08/16/2009 11:51:37

JimB517
Past Commodore

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USA
3285 Posts

Response Posted - 08/16/2009 : 16:47:21

even with good bottom paint you still have to have a diver clean the bottom monthly - especially in summer

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Dave Bristle
Master Marine Consultant

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Djibouti
10005 Posts

Response Posted - 08/16/2009 : 18:09:50

<blockquote id="quote">quote:<hr height="1" noshade id="quote">Originally posted by JimB517
 ...you still have to have a diver clean the bottom monthly...<hr height="1" noshade id="quote"></blockquote id="quote">That's the association's #1 ocean racer speaking. With dual biocide ablative paint, my C-25 hardly accumulated enough slime to see over an entire season. It made no discernible difference to me, but I didn't race her. Different strokes...

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