Yamaha 15 HP Motor.-

[Sea Rider]

A friend of mine who has been powering a 430 Mt Rib with a 2 strokes Yam 15 HP motor for several years while mixing 50:1 fuel/oil ratio which is around 80 Ml per gallon, decided in his last outing to mix 80 ML per 4 gallons, that's just 20 Ml per gallon after watching a YouTube video.

Next day while boating to a near islet his motor suddenly stopped while revving at some speed, was impossible to be started again. For his luck a Samaritan passing by towed the combo to Terra Firme. Assures his motor is not jammed so tomorrow will perform a compression test to check if the piston rings have been squeezed tight along a spark plug test to determine if it's a mechanical or electrical issue.

Don't believe all what YouTube videos shows, there are people out there who don't even know where they are standing....

Happy Boating​

 

[robert graham]

So he reduced his oil/ gas ratio by 75%?….why did he do that?…..hopefully his motor is not seized but if it will run at all then maybe go back to the old/ normal mix and hope for the best…

 

[Sea Rider]

So he reduced his oil/ gas ratio by 75%?….why did he do that?…..hopefully his motor is not seized but if it will run at all then maybe go back to the old/ normal mix and hope for the best…

Yep, was wondering same, crazy to have reduced the motor's oil/fuel ratio from 80 Ml to 20 Ml, will check latter if there's a YouTube video on that matter, my friend surely had a Senior Moment LOL!!

Happy Boating​

 

[boscoe99]

Yep, was wondering same, crazy to have reduced the motor's oil/fuel ratio from 80 Ml to 20 Ml, will check latter if there's a YouTube video on that matter, my friend surely had a Senior Moment LOL!!

Happy Boating​

 

[QBhoy]

Sounds a strange mix to go to. I know that some of these were originally 100/1 back in the day. I’ve a few old Yamaha 2 strokes that specify 100-1 but I always mix them 50-1 these days.
But to drop from 50-1 to near 200-1 is crazy advice to give out.
But…all that said…he may still be lucky. These old Yamaha engines are about as tough as they come. Known to run with no oil through them…no cooling through them…and even after seemingly failing or stopping…after some careful first aid and oil soaked…they can recover remarkably afterwards. Tough as they get.

 

[Sea Rider]

Actually it's a 5 year old Yam 15 with low hours use, this model is still being manufactured in Japan and sold in countries that have not banned 2 stroke old technology. In my last wish I will include being buried with one. LOL!!​

The basic troubleshooting : fearing having seized piston rings due to having run the motor with 200 :1 oil/fuel ratio a compression test showed 112 PSI on both cylinders, both Ignition Coils were firing healthy, thumbs up!! What's next : fuel system. Cleaned the tank's interior and mesh filter, the motor's fuel filter next to the fuel pump, proceeded to prime the bulb hard with arrow pointing upwards while maintaining the motor's connector pressed open for a spot on fuel purge into a container. The hose was found with a severe fuel restriction due to being left with fuel for more than a year. A long fuel purge fixed it.

The motor was found with both spark plugs gaped to insane 1.3 mm, were re gaped to 1.0 mm tight. This motor was fully serviced by the Yam dealer a week ago, both spark plugs were charged in the bill, but to me were never changed, pic says it al...​

It's impossible for both "new plugs " to show such carbon build up along a darkened yellowish center with just 2 run hours at 200:1 oil/fuel ratio. For my friend's peace of mind will install 2 new NGK-BR 8HS-10 next week.

Lastly, poured 160 Ml of Yamalube oil in the tank to complete the 50:1 oil/fuel ratio that nice motor works with. Well primed, the motor started right up at second pull and remained ON for a 10 minute barrel test, tomorrow will be tested at open waters. Find this motor to have been badly designed at the factory, doesn't count with both lower leg's water intakes so impossible to be flushed on muffs, but does have a water plug located on the lower leg which will need to be unscrewed each time wanting to flush the motor with fresh water.

Happy Boating​

 

[QBhoy]

Actually it's a 5 year old Yam 15 with low hours use, this model is still being manufactured in Japan and sold in countries that have not banned 2 stroke old technology. In my last wish I will include being buried with one. LOL!!​

View attachment 354763

The basic troubleshooting : fearing having seized piston rings due to having run the motor with 200 :1 oil/fuel ratio a compression test showed 112 PSI on both cylinders, both Ignition Coils were firing healthy, thumbs up!! What's next : fuel system. Cleaned the tank's interior and mesh filter, the motor's fuel filter next to the fuel pump, proceeded to prime the bulb hard with arrow pointing upwards while maintaining the motor's connector pressed open for a spot on fuel purge into a container. The hose was found with a severe fuel restriction due to being left with fuel for more than a year. A long fuel purge fixed it.

The motor was found with both spark plugs gaped to insane 1.3 mm, were re gaped to 1.0 mm tight. This motor was fully serviced by the Yam dealer a week ago, both spark plugs were charged in the bill, but to me were never changed, pic says it al...​

View attachment 354764

It's impossible for both "new plugs " to show such carbon build up along a darkened yellowish center with just 2 run hours at 200:1 oil/fuel ratio. For my friend's peace of mind will install 2 new NGK-BR 8HS-10 next week.

Lastly, poured 160 Ml of Yamalube oil in the tank to complete the 50:1 oil/fuel ratio that nice motor works with. Well primed, the motor started right up at second pull and remained ON for a 10 minute barrel test, tomorrow will be tested at open waters. Find this motor to have been badly designed at the factory, doesn't count with both lower leg's water intakes so impossible to be flushed on muffs, but does have a water plug located on the lower leg which will need to be unscrewed each time wanting to flush the motor with fresh water.

Happy Boating​

Got you. That will be a great engine. Haven’t changed a bit since the late 80’s. She’ll be fine. Only issue I’ve ever had with mine is salt deposits building up in the cooling passages, from previous owner not flushing after a season. Will run forever these things.

 

[Sea Rider]

Got you. That will be a great engine. Haven’t changed a bit since the late 80’s. She’ll be fine. Only issue I’ve ever had with mine is salt deposits building up in the cooling passages, from previous owner not flushing after a season. Will run forever these things.

All motor brands used in salt water and not flushed with fresh water soon after returning will collect huge salt layers which will decrease the motor's diam passages to cool properly. It's called saltesclerosis which will need to deal with. Any motor well cared for and properly maintained should run forever....

Happy Boating​

 

[QBhoy]

All motor brands used in salt water and not flushed with fresh water soon after returning will collect huge salt layers which will decrease the motor's diam passages to cool properly. It's called saltesclerosis which will need to deal with. Any motor well cared for and properly maintained should run forever....

Happy Boating​

Agree…apart from the odd Seadoo jet skis engine