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Tan
Tan, MerCruiser Certified Technician
Category: Boat
Satisfied Customers: 10903
Experience:  40 yrs. experience with complete engine repairs both inboard/outboard and MerCruiser Certified Technician.
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I have a 25 hp mariner that last year would not start and the

Customer Question

I have a 25 hp mariner that last year would not start and the solenoid was bad. replaced and did fine. this year same problem, hard starting first time,but went out and did fine. tried another day and has yet to start. replaced solenoid again but will not start at all. Engine is firing, fuel going into filter but pumps up very hard. barely can get filter full. Is there another location that is blocking fuel or something else. I burn only non-ethanol fuel.
Submitted: 2 years ago.
Category: Boat
Expert:  Tan replied 2 years ago.
Hello. My name is***** you say will not start which part won't turn the flywheel or won't fire as in no spark? Could I get the engine serial number please?
Customer: replied 2 years ago.
Engine cranks as should. Plugs are firing. Fuel is pumped up in filter and bulb is tight when pumped up.
Customer: replied 2 years ago.
Boat is not here for me to get serial#
Expert:  Tan replied 2 years ago.
Will the spark jump a 7/16 " gap on a spark gap tester? If you squirt fuel intop the carb will it fire up?
Customer: replied 2 years ago.
I'll have to go there and see. I have a tester somewhere I think. Fire is blue on plugs when firing. I"ll check that and get serial#. Be tomorrow before I can get back to you. 15miles to location.
Expert:  Tan replied 2 years ago.
Yeah testing at the plug doesn't give us the strength of the spark. It can show spark but under compression it won't fire. This is why it has to jump a 7/16" gap to fire under compression. We could have weak output from the stator and the spark just isn't strong enough. Take as much time as you need there are no time limits.
Customer: replied 2 years ago.
Motor serial# ***** ***** I found my gap tester and spark is good. I did put gas in carb and the engine did fire up. Brought boat home so I can move on. Thinking I have a blockage in the carb unless something else is not allowing flow. Used it 2 weeks ago. Hard starting at first but no problem after that.Does not add up to me to be carb.
Expert:  Tan replied 2 years ago.
Yes the carb is the issue. You have stuck inlet needle not allowing fuel into the carb. Remove the carb,disassemble, clean and install carb kit # ***** The idle jet adjustment is 1.5 turns from lightly seated then when in the water warmed up adjust in small increments to achieve best idle.http://www.boats.net/parts/search/Merc2/Mariner/25%2C%2025%20MARATHON%2C%20SUPER%2015%20%282%20CYL.%29/0G044027%20THRU%200G760299/Carburetor%28SeaPro-Marathon%2015-25%20%26%20Super%2015%29/parts.html We also need to check the choke make sure the choke plate is closing completely. We can check this after you have done the carb as the carb rebuild may solve the hard starting. What can happen if an engine has been sitting for awhile it will run good the first couple of times out. Then the fresh fuel has had time to dissolve the old fuel residue in the carb which now has fallen in to the jets and portsd clogging the carb causing the engine to run poorly and eventually no start. This should do it for you post back if you need further assistance. Thank you Tan
Customer: replied 2 years ago.
Thanks. I'll get started in that direction. That does make good sense to me. I'll let you know how it turns out.
Expert:  Tan replied 2 years ago.
Ok great.

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