25hp Johnson (part 3)

[monster1]

Took the boat out again yesterday. Came back in with a headache from the exhaust fumes. Noticed I burned over a gallon of gas to go 4 miles. Is this expected mpg for old two stroke technology in a small outboard? It's double what I get with my 21 walkaround with volvo penta. Not complaining about the mileage, just wating to make sure the motor isn't burning excessive fuel.

Also, PO plugged up one of the exit ports on the choke solenoid so that only one line comes off it. That line is run to a tee which sends one line to the top of the carb and the second to the bowl. I put the red lever in the correct position facing towards the solenoid when I was tying up lose wires the other day. Leaving it in that position wouldn't allow the motor to start when I went out yesterday. Putting it in the position it was in when I bought the boat fired it right up.

This doesn't seem right to me. As previously stated, I don't want to fix it if it's not broken. But if this isn't right, I want to fix it. Seems like the motor wasn't running for the PO so he bypassed the choke solenoid allowing fuel to constantly be pumped to the top of the carb. Does this sound correct? I told myself I wasn't going to worry about it thinking I was going to repower with a 4 stroke. But a new 4 stroke is going to cost more than I paid for the boat. I think I'll stick with what I have. Thanks again for all your help.

 

[nwjones18]

I don't recall what year your Johnson was, but I had a 75 model 25hp for several years and it was a headache pretty much all of the time.. It still had good compression when I sold it, but I was always messing with the carb, points or vacuum leaks hear or there. Had the threads come out with the spark plugs and had to helicoil the head.. All that said when mine was running right I could run around in my 16ft jon boat pretty much all day on 5 gallons, but no idea how many miles I actually covered. I got a chance to get a low hour 2003 2 stroke Mercury 25hp and I can say that is better in every way than my much older Johnson.. Gets on plane faster, starts easier and is quieter. Although its still very loud compared to a 4 stroke. I'd say fuel economy is pretty similar between the two.

 

[Egg_Head]

Are there no reputable outboard motor mechanics near you? Find someone with gray hair who knows these engines and get it properly sorted out.

 

[monster1]

Are there no reputable outboard motor mechanics near you? Find someone with gray hair who knows these engines and get it properly sorted out.

Sorry. Didn't know what I was thinking.

 

[Donald]

And post under Boating.

 

[monster1]

And post under Boating.

Right away sir.

 

[monster1]

Just thought I'd update. After finding an old service manual, I pulled and rebuilt the carb. Adjusted the linkage and set the idle. Cleaned out the choke solenoid and replaced all fuel lines. It's behaving like a completely different motor now. Compression verified at 91/90. Time to go fishing.

 

[Hillbilly Deluxe]

Good job. But know there's a reason why OMC isn't in business anymore. People got tired of their stuff. Not saying they didn't build powerful marine engines, but they just weren't up to par with Yamaha nor Mercury. Mercury had to improve their quality and they did. They de-organized and de-"GM'ed" their company, dropped the Mariner stuff and concentrated on going after the offshore market and they are now competitive with Yamaha.

I own two boats with Mercury-power. One is a 1997 Sea Ray with a 7.4L and Bravo III and the other is a 2016 Ranger with a 175 Verado. Both are fantastic.

 

[monster1]

Peculiar how if it's not running it's a good motor, but if it is, it's an outdated pos. Man, people are strange.

 

[Hillbilly Deluxe]

Peculiar how if it's not running it's a good motor, but if it is, it's an outdated pos. Man, people are strange.

I don't know who this is directed at, but I assure you it doesn't take too many times of being stranded on the water to get a bad taste in your mouth for a boat motor.

 

[monster1]

I don't know who this is directed at, but I assure you it doesn't take too many times of being stranded on the water to get a bad taste in your mouth for a boat motor.

Thanks for your output.

 

[Hillbilly Deluxe]