Mechanics didn't know squat when it came to my 2.5hp Mercury outboard

Senkosam
Senkosam
Active member
I've spent as much $ fixing a starting problem as I did the motor, not including truck gas to transport to the shops.
When I went to pick up the motor, it would start in the shop but not on the transom of my small boat. I took the motor off and let it sit on a wooden horse outside for weeks, disgusted.

You know the feeling when, out of the blue, an idea comes to you that fixes a problem bugging you? This was that time!
Note: When the motor didn't start, it was under the hot sun of Aug.
Note: When it started every time, it was in a cool shop.
Note: the manual says to start the motor: choke all the way out/ gas valve turned on/ throttle to start position on the handle/ vent on top opened/pull handle

Did that a million times and nothing. But an idea came to me after I opened the gas cap to see how much gas was in the tank. WHOOSH! - air going into the tank relieved a vacuum caused by the heat of the sun. The vent wasn't working!
Okay, so I loosened the gas cap and IT STARTED! Not only that, but it idled at the lowest speed - which in the recent past would stall and not start no matter what.
*One thing I noticed to start the motor, along with a loosening gas cap, was playing with the choke. Rather than full out, I out, I did a half choke position. Started and idled great until it started to stall at which point, I pushed it all the way in and let it idle for 15 minutes. After that, I turned off the motor and then started it again and again and again! The next day, no problem starting and idling, but only when the gas cap was loosened.

Something about the vent on the gas cap not allowing air into the tank when open, didn't allow gas to go into the carburetor due to a vacuum caused by the gas. If only water had been in the tank, I doubt the vacuum would have happened.
Also, the choke, for whatever reason, had to be halfway in when starting - not full choke.
(Note: the motor was always in a bucket of water to prevent damage.)

But get this! When I gave up on the motor, I ordered a Newport 62# thrust trolling motor and tried it on the lake, MAN DID THAT SUCKER MOVE MY 12' JON BOAT WITH ALL MY GEAR AND AT 20 MPH! I took a friend fishing and it did the same speed fishing out of a 12' heavy aluminum boat I rented. We did about a mile on the way back in no time! The battery was only down to 55% displayed on the charger - and that was after slowly fishing many areas for hours (until it got too hot). Guess I may as well sell the gas motor cheap on Facebook Marketplace rather than spend over $20 for a new gas cap.

Strange that an idea out of nowhere, finally solved the problem - (like using a 1" soft plastic (the tail cut off a plastic worm) on a 1/64 oz jig, to catch nipping juvenile 4-5" fish.)
 
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Senkosam said:
I ordered a Newport 62# thrust trolling motor and tried it on the lake, MAN DID THAT SUCKER MOVE MY 12' JON BOAT WITH ALL MY GEAR AND AT 20 MPH!
Impressive.😉
 
I thought my Minn Kota 55# thrust was powerful. This one at #1 setting is equal in speed to the Minn Kota's 2nd speed.
But now I've got the 2.5 hp Merc starting/idling okay, I may as well try it on the lake.
 
The Mercury motors 30 hp and smaller are Tohatsu made, super good motors, but if you need assistance, I believe St. Johns Marine Services has been the Tohatsu dealer for some time and their parts are cheaper than the Mercury catalog parts.
 
Update:
A buddy from my fishing club told me about a guy who fixes outboards from his garage. Granted, he was 35 min. away but well worth the trip! I towed the boat along with the 2.5hp. He ordered parts for both, which took over a week. Once they were both done, I was shown the old parts that needed replacement and he explained the function of those parts and why they prevented starting. The new starting battery that cost over $200! that hadn't been hooked up to the 40hp (just as I thought), was now wired to it. He tested the stator (alternator) and said it was fine to charge the battery when the motor ran. But, he suggested doing a trickle charge if the motor wasn't used for over two weeks or more - same for the separate trolling battery. (*thoughjt it was kind of expensive for a new starting battery.)

He also made other improvements that I asked him to look into and gave me reasons why the previous owner's modifications were unnecessary (i.e. too many wires going to the wrong places.) Now both start instantly and idle smoothly. Granted, it cost over $800 between parts and labor for the two motors and rewiring, but he also included a guarantee that if the same problem occurred this year (2026), he would gladly fix them - n/c - unlike the other three clueless rip-offs.

Finally, peace of mind!!!
BTW, I asked him about the cool T-shirt he was wearing showing his name and number. He gave me and my buddy who towed me to his shop, two for free and we promised to wear them to advertise his great service. Funny though, his service is called
Capt. Dan's, LLC / Maintenance & Repairs
capt dan.jpg

(Fooling around, I asked him when he was promoted. You know, like from Lt. Dan from Forest Gump? He didn't get it.)
 
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