1975 Johnson 70 HP having problems

" I have a 1975 Johnson 70 HP

" I have a 1975 Johnson 70 HP that all of the sudden will not run full speed. One day I took it out to the lake and it started and ran full speed to a spot and I fished for about 25 minutes. Went to change positions and it would not run full speed. The throwtle was wide open but the boat was running very slow. Don't really know where to begin on checking for a problem. Did check fuel filter and lower unit oil. I am replacing the spark plugs but do not know what else to check. Help would be greatly appreciated.
Also, is the fuel mixture for this engine 50:1 ratio. I thought this might be the problem. Too much oil? "

"Geoff.... Whenever problems a

"Geoff.... Whenever problems arise, always check the compression first, then the spark which should jump a 7/15" gap with a strong blue flame. If those two items are as they should be, the problem is usually fuel related.... either a fuel restriction, air leaks, or faulty carburetor. It's a good idea to make a note as to what s/plug came out of what cylinder. They should all look alike.... a plug being different would make one look closely at that particular cylinder. Let us know what you find.

Joe "

I have a 1999 3cyl Johnson 25

I have a 1999 3cyl Johnson 25HP short shaft. Last Fall when boating after markers pulled hit a reef wide open. I had a rock hopper motor guard on which took a majority of the blow. I started it the other day with the muffs on and noticed water coming out in front at the union of the lower unit to the upper motor. She spits normally and everything runs fine. Is it normal to water coming out at the union between the upper and lower unit if front on these motors? What advice do you have? Will I hurt the motor to run it this spring?

Geoff, I had the same problem on my 70ESL75. Could not get to high speed! Turns out the carb's hi-speed jets draw from the sump in the bottom of the bowl and that is where crud builds up first. The lo-speed jets draw from higher in the bowl. So the first thing that fails is your hi-speed, while the lo-speed is OK. Good engineering design, fails just enough for you to get back to the boat ramp!

Clean those carbs!

jtalics ----That was 16 years ago------I am sure these posters have resolved their problems !!

I noticed that, but my reply could help current boaters reading this thread with the same problem.
Especially with searchable keywords: 70ESL75, 70ES75.