Yamaha 25 HP 4 stroke problem

[Clambone]

Hi everyone, I have a Yamaha 25 HP 4 stroke (F25MSHA) #152615 year bought 2002. I used it first time last year and after running perfectly it suddenly wouldn't start (on a morning where it had been running fine). I pulled the plugs and cleaned them to no avail and eventually after checking as much as possible took it into a dealer who quickly diagnosed bad spark plugs (I had assumed new spark plugs wouldn't need changing so hadn't changed them). I winterized the engine and it ran fine. This year I just got it out and it started up fine and ran well for maybe 2 hours of on and off running until today it again suddenly died. I pulled the plugs and they seemed to have a few drops of water on them. The fuel was clean new fuel into a clean tank this week. I even filtered the remaining to fuel to make sure. Seems like it might be a serious problem. Any clues?

 

[JB]

Re: Yamaha 25 HP 4 stroke problem

Belongs in Yammy troubles.<br /><br />Moving it there.

 

[huanca]

Re: Yamaha 25 HP 4 stroke problem

clean your carbs

 

[Clambone]

Re: Yamaha 25 HP 4 stroke problem

Seems the problem in fact was the weight of the 25HP which drove the transom too low when i was in hauling on lines back aft. If I had left the motor running it would have been fine but having stopped the motor water was able to get in through the exhaust. so its either a question of leaving the motor running when hauling or tilt the motor up before stopping and get crew weight forward too. 2 strokes being lighter rarley sufferd from this problem I suppose.The other solution is a taller transom and a longer shaft.

 

[myriopod]

Re: Yamaha 25 HP 4 stroke problem

The 2002 engine you are talking about may be carberated and not fuel injected, if so you may have to manually choke it. There should be a manual choke pull lever near the tiller.

 

[barancig]

Re: Yamaha 25 HP 4 stroke problem

I have the same motor (2001 version) and a similar problem. The motor starts fine when cold, but if I stop and try to restart, it's very difficult to start (I have to keep cranking and play with the choke to get it to start). I've also replaced the plugs, checked the fuel line and replaced the fuel.<br /><br />I thought/hoped that I might also have a "low engine" problem...I have this engine on the back of an 11' RIB inflatable and it does sit rather low in the water. However, I've also found that when I've been running the engine for a while, it tends to stall if I throttle down to idle for more than a couple of minutes. So, I'm not sure that water getting in through the exhaust is the answer (i.e., stalls even when running). <br /><br />I'm not knowledgeable about engines but I did ask my marina to check out the engine thoroughly a few months ago and they couldn't find anything wrong...other than some dirty fuel which they changed...and replacing the old plugs.<br /><br />Any other suggestions on what I might try?

 

[rodbolt]

Re: Yamaha 25 HP 4 stroke problem

hello<br /> there is a tech bulliten out on modifying the exhaust on some 25hp 4 strokes due to sitting to low in the water.<br /> good luck and keep posting

 

[bigbrownbuku]

Re: Yamaha 25 HP 4 stroke problem

the bulletin is for applications sspecific to what you mention. there is a relief hole on the exhaust tube that was found to be the culprit, this hole was moved higher and baffled. you may even get it under warranty? cant hurt to ask.

 

[Clambone]

Re: Yamaha 25 HP 4 stroke problem

Rodbolt & BenC: where can I download this bulletin from?<br /><br />Myriopod: no its injected fuel, no choke<br /><br />Barancig: you are right if shes running then its not an exhaust problem. The dirty fuel could be the problem. How has it run after that was changed?<br /><br />I've been running this motor quite a bit since the last post and as long as I leave it running I have had no more problems.