# 25hp yamaha problem



## hoffy (Jul 30, 2015)

have a 2002 yamaha 25hp 2 stroke 3 cylinder  
Here's what's going on
I run the boat about 10 min to my fishing spot and turn motor off Runs good . Start motor again and probably run for 3-5 min and then it boggs down feels like it's dropping a cylinder. Sometimes I can turn motor off and back on then it will run a little longer before it happens again.  thoughts?

Carbs have been rebuilt 
New tank, lines and connectors
Compression is 150 on all 3
Plugs are not wet  
Not overheating 
I use 100/1 ratio 
Help please.  Thanks in advance


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## hwew (Jul 30, 2015)

Is the vent cap on the fuel tank open? Oops, I see you purchased a new fuel tank. Is it the EPA/CARB compliant tank? If it is, is the cap allowing air in the tank properly when the engine is running? My understanding is the new fuel tank caps do not vent freely. There will be a slight vacuum in the tank. I wonder if the fuel pump is not functioning properly with the slight vacuum in the tank.


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## hoffy (Jul 30, 2015)

Yes vent is open I think it's an electrical issue


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## turbotodd (Aug 4, 2015)

I've had to replace a few coils on those. And CDI's. next time it wants to bog down and try to die, try this. First, pull the choke out while it's dieing. If it takes off, it's a fuel problem. If it doesn't, pull the cowling off and tap the side of the CDI. If tapping the CDI makes it run like it's supposed to, then you'll want to pick up a CDI for it. If not, one of the coils.

Gotta be careful in diagnosing this way! Don't be stupid. Keep the lanyard hooked onto your belt loop or life jacket.

They are fast, but they are also money pits. I miss the speed and torque of the triple, but I don't miss having to work on it every other time I used it.


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## Captain Ahab (Aug 5, 2015)

P_lease add your location to your profile


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## hoffy (Aug 9, 2015)

Installed new diaphragm. So far so good thanks for the replies


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## hwew (Aug 12, 2015)

Was the diaphragm torn, or swelled up?


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## hoffy (Aug 27, 2015)

Not getting a good seal


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## crazymanme2 (Aug 27, 2015)

I would run 50:1 on that motor.


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## hoffy (Aug 28, 2015)

Can you give me some details why ?


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## crazymanme2 (Aug 28, 2015)

100:1 is just not enough oil to properly lube an outboard.They used to have 100:1 but changed for that reason.
Surprised nobody else chimed in on this.


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## Pappy (Aug 28, 2015)

In an engine that is run frequently, not run hard and everything is perfect on it....all the time....then 100:1 can be run. 
That is in a perfect world. 
Things happen. 
If a high speed jet gets a tiny piece of debris in it.
Fuel line gets kinked to the engine.
If you make a mistake and overheat the engine.
If you purchase gasoline that has less than the recommended octate or too much alcohol in it.
If any of these occur then 100:1 is not your friend. There will not be enough oil to protect the engine from disaster.
That ratio was a marketing decision, not one that came from Engineering.


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## hwew (Sep 5, 2015)

crazymanme2 said:


> 100:1 is just not enough oil to properly lube an outboard.They used to have 100:1 but changed for that reason.
> Surprised nobody else chimed in on this.



Was this Yamaha? My understanding is they still recommend 100:1. If it is Yamaha than this is some news that I did not hear.
I do know that Evinrude / Johnson used to be 100:1 and decided to change to 50:1 but that was quite a few years back.

I was thinking of trying 100:1 on my Yamaha 25hp 2-stroke twin but decided not to rush into it. I'm still running 50:1.


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## Pappy (Sep 6, 2015)

That would be a very wise decision on your part!


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## tomme boy (Sep 6, 2015)

What happened to the oil injection that was on the motor?


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## hwew (Sep 7, 2015)

The 2005 Yamaha 25hp 2-stroke twin never came with oil injection.


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## tomme boy (Sep 8, 2015)

Its an 02 3 cyl from what he listed so yes it had oil injection.


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## uglymud (Sep 15, 2015)

I run a 98 3cyl and run 50:1 don't have any problems with it. If you're looking for a little more power out of it throw some 30hp jets in there. Little motors will scoot if you know what to do with em.


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## turbotodd (Sep 18, 2015)

I wasn't aware that any of the triple cylinder 25's had oil injection. 40's yes (P40 and some of the 40's but never the C40, IIRC) but I don't remember the 25 having it. Twin cylinder twin carb up to 2001 I think, yes but later no.

Yamaha was 100:1 up to 40hp, up until 2009 when the 25 2 stroke was discontinued. They will run forever at 100:1 as long as the oil is good quality Yamalube or equivalent.

The triple 25 can make up to about 80 hp give or take, depending on how far you want to go with it. They are mod-friendly but the more you do, the less reliable they get. Experience speaking. Had one, it was fast and fun but I worked on it as much as I got to use it. Change jetting with big weather swings among other things.

The stock motors, un-modded, can bring a lot of money to the right person. WAY more than any other Yamaha 25. I saw one recently...clean, bone stock, sat more than it got used...sold for $3100. Motor alone, no boat.

I think some of the 30hp and I know for sure some of the 40's had Autolube. In this area, many of the 30's and 40's were used as "25hp" by changing the cowling, from the 30 or 40hp cowling to the 25 3 cylinder cowling. Lot of the public duck hunting areas are 25hp max. Game commission got smart and started checking the serial numbers. 6H4 serial prefix was 40hp. And a lot of them had the actual model number on the tag (e.g. 30ETLJ which would be a 30hp). The triple 25, the 30, and some of the 40's were the same block, same foot, same mid section..different carbs, ignition, reeds, and tuner, among other smaller differences. Actually thats why they're worth more in this area. The duck hunters (boat racers) love the 3 cylinder model. Have spoken to many who have driven a thousand miles (literally) to buy them from east coastal areas, even some going to Minnesota, Wisconsin and one went clear to Idaho to buy one. They're crazy about them out here. Duck hunting...in this area...is a rich man's sport anyway and the spoiled rich kids drive for days, buy the motor they wanted, bring it back and the first time out in the flooded timber, run over every log, stump, tree, booskios, run it aground, and just destroy it. All this while trying to be the first one to the "hole", hence the mods.

Another good one is the Suzuki DT25, once you get past the short tiller.

Just amazes me that people will get crazy over those two motors, even the manual start models. Guess I am spoiled now with electric start. The Yamaha 3 clyinder was only made a few years (97-02 I think) and they were all manual start. Electric not offered to my knowlege, so if you find an electric start 25 3 cylinder, it's probably either been converted or it is a 30 or 40 with a 25 cowling.


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