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Jason
Jason, Marine Mechanic
Category: Boat
Satisfied Customers: 16209
Experience:  Degree in Marine Technology. Gas and diesel marine mechanic.
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I have a 1988 yamaha 115 2 stroke new power pack replace

Customer Question

i have a 1988 yamaha 115 2 stroke new power pack replace year ago, rebuilt carbs new fuel pump. has been a strong motor. Now it stalls out past low throttle.. the coils show 125 ohms and one of them at 388. the book calls for 388 to 588 on the coils. would this cause a break down under load I first though it was a fuel issue .
JA: Sometimes boat issues seem like they'll be really complicated, but end up being easy to fix. The Marine Mechanic I'm going to connect you with knows all the tricks and shortcuts. Is there anything else the Marine Mechanic should be aware of?
Customer: also i have tested the power pack at all points on output. the oil tank on the motor is filling up ok so i dont expect the saftey mode. The motor starts off with fair power and then bogs all the way down . that is why i first though fuel. jim
Submitted: 1 month ago.
Category: Boat
Customer: replied 1 month ago.
Posted by JustAnswer at customer's request) Hello. I would like to request the following Expert Service(s) from you: Live Phone Call.
Customer: replied 1 month ago.
Let me know if you need more information, or send me the service offer(s) so we can proceed.
Customer: replied 1 month ago.
Let me know if you need more information, or send me the service offer(s) so we can proceed.
Expert:  Jason replied 1 month ago.

H​I Jim, good morning my name is***** you have a timing light so that we can check and see if that cylinder is sparking or not. Do you also have a model number on the outboard?

Customer: replied 1 month ago.
hi jason, I checked each cylinder with my spark checker, glass tube with the gap set at 1/4 inch spark is thin, but blue. It could be weak under load. The coils tested out at 127 ohms with one at 380 specs call for 388 to 580. the model number of this motor is 115etlg code 6esl 2 stroke yamaha
Expert:  Jason replied 1 month ago.

1/​4 in inch would not be a large enough gap. Can you set the gap to 7/16ths of an inch and see if the spark jumps that gap?

Customer: replied 1 month ago.
ok i adjusted my spark checker to 1/2 inch and checked each cylinder with the motor running. the spark jumps the gap, but is red in color is that weak or ok for this system. jim
Expert:  Jason replied 1 month ago.

T​hat would be on the weak side. It really should be hot and blue, like little lightning bolts. The best way to check for spark is with a timing light. What you would want to do is get a timing light (they are only 20 bucks on amazon) and hook that light up to each plug wire one at a time, and see if the light flashes or not with the engine running. If the light does flash, then that plug is in fact firing while under a load. If the light does not flash, or is flashing eratically, then there is no spark or the coil is misfiring on that cylinder. Does that make sense.

Customer: replied 1 month ago.
ok jason i checked the spark while running with my timing light. steady flash on each cylinder. I still question the low ohm reading on the coils. jim
Expert:  Jason replied 1 month ago.

Please bear with me as we are not having a face to face or phone conversation. What is your question about the low ohm reading specifically?

Expert:  Jason replied 1 month ago.

It looks like you read my answer and left without selecting a rating for my service, replying back, or simply thanking me. Was there something else?

Customer: replied 1 month ago.
thanks for the tips i did not realize that using a timing light would be a better indicator of spark than the flash tube the ohm value on the coils is still reading well below specs the coils are reading 127 to 190, with only one showing 388 ohms. book calls for 388 to 588 ohms, so i ordered a set of coils. jim
Expert:  Jason replied 1 month ago.

Coils can technically be "out of spec" but still fire. The timing light is the better test to see if those coils are actually firing when under a load. Was there anything else?