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Need some advice on old Johnson 70ESL74M

F

Frickinfrack

New member
Thank you for letting me join. I have voiced these questions in other groups with no real solutions so I figured I'd try here. Hoping there is someone on here that has dealt with one of these. Ok here goes.

My wife and I were given a 1964 Searay 700. It's a 16 footer and it in great shape due to being in a showroom for 10 years, used 2 seasons then garaged for the rest of it's life. I have finally made it through troubleshooting and ignition problem after replacing all 3 plugs, all 3 coils, and finally the CDI box (Power Pack 3).

It runs pretty good but has trouble getting up on plane. I can get her up when she's just started but after a run of about 15-20 if I drop down she will just plow. I'm guessing it's the power jets but really really don't want to tear the carbs apart. The linkage scares me and I'm cheap so paying someone is only an absolute last resort. Is there a magical fluid I can run through her that might clean them puppies out?

On to my next set of issues. Everyone I have spoken to says that this OB has manual tilt and putting power tilt on is a bear. Basically DIY and hope it works. I have a picture (that I can't seem to upload) that shows, what I think is, a lift cylinder with a broken part on the bottom. Am I seeing things or is it just something else? If that is a lift cylinder then it would have power tilt, right?

And finally, I'm currently using a 14 by 9 prop and would like a better hole-shot. I don't care about top speed at all. 15-20 is plenty for me. Any idea how much I should drop the pitch to give me the best throttle response with a top speed of about 20-25. I know I'll need to play with it but am looking for a staring point.

If anyone can tell me how to upload the pictures, I'd be happy to do so. I already tried the button up top as well as the manage attachments below. Jpegs are 6 Megs each. Maybe too big? I'm sure they will help with the lift cylinder thing question.

Any insight by someone who is familiar with the motor or boat or motor/ boat combo would be very much appreciated.
 
14 x 9 is absurdly low pitch in my opinion. If you don't have hole shot with that, something is wrong. Make sure it is running on all 3 cylinders. Begin with a compression test to see if you have anything worth fixing. Then, yes it is possible the high speed jets are clogged. But that is just a "maybe" among other things.
 
I had the exact same problem except mine would not plane from the start. Sounds like it may be starving for fuel, on mine the lower carb was not getting any fuel at all. I replaced ALL the fuel lines including the tank line, removed the carbs one at a time so not to mess up the linkages, opened the carbs and cleaned them. While your doing that check the compression, I have 130 on all 3 cylinders. If you remove the carbs one at a time just pop the linkages out of the plastic holders on the carb your working on. I just put my boat back in the water last weekend and now it will plane almost instantly and do 30+MPH. I'm running a 13x19 prop. Just be very careful because if one of the cylinders are starving for fuel you can damage the motor quickly. Hope this helps.
 
@fdrgator - Maybe it's 14X19, it's whatever the OEM recommended and yes definitely something wrong. Had a couple 2 stoke triples motorcycles and thins motor doesn't have that angry sound the triple are know for. Comp test done last October. Was 120ish for all 3. I'm thinking of running some seafoam or something like that through it hoping it will get the snot out of the jets. Have you had any luck doing something similar? Any reason to not use a "fuel system cleaner" on a 2 stroke? I can't think of one but, I don't know everything either. It hasn't had all it's horses since I got it about 2 years ago but it is getting better. Just not quite there yet.
 
Simple fact for you.-----Each carburetor feeds one cylinder.----Next simple fact.----If a carburetor is restricted / plugged it may starve the cylinder of fuel.----And also starve that cylinder of oil !!------Next thing you would be shopping for another motor !
 
I tried seafoam, good product but didn't help with my issue. If the tank ever had a grey fuel line you may have some debris in the carb. Also check the fuel filter which is very easy. Just unscrew the front round brass knob with a flat head screwdriver and check the screen inside.
 
If you really feel the high speed jets are clogged, they are easy to inspect without removing the carburetors. Remove the intake silencer, and the jets are behind the hex drain plugs in the carburetor bowls. You are supposed to use a special screwdriver to get them out without damage. Or make your own screwdriver. Or get lucky.
 
fdrgator said:
If you really feel the high speed jets are clogged, they are easy to inspect without removing the carburetors. Remove the intake silencer, and the jets are behind the hex drain plugs in the carburetor bowls. You are supposed to use a special screwdriver to get them out without damage. Or make your own screwdriver. Or get lucky.
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I'll pull it off and look. Thanks!
 
racerone said:
Simple fact for you.-----Each carburetor feeds one cylinder.----Next simple fact.----If a carburetor is restricted / plugged it may starve the cylinder of fuel.----And also starve that cylinder of oil !!------Next thing you would be shopping for another motor !
Click to expand...

I'm 99% sure all 3 are firing so they must all be getting gas, right? I know this because I have pulled each plug wire one at a time while running and it made a difference with each one. Got zapped a few times too so I am confident the spark is good and strong! It idles and goes all the way up to about half throttle nice and smooth. Push the throttle any farther and it doesn't really do anything. I have verified that the butterflies are opening all the way. I'm just trying to avoid tearing the carbs apart. Plan is to try some Seafoam and if that doesn't work, I'll have to tear them down. Tiny parts and old eyes don't usually go together.
 
Pushing the throttle further with no response is exactly what was happening to me.....Sounds like its staving for gas. Fuel lines and a fuel pump are cheap, if the motor has never had a carb service it due anyways, especially if it has been sitting.

Frickinfrack said:
I'm 99% sure all 3 are firing so they must all be getting gas, right? I know this because I have pulled each plug wire one at a time while running and it made a difference with each one. Got zapped a few times too so I am confident the spark is good and strong! It idles and goes all the way up to about half throttle nice and smooth. Push the throttle any farther and it doesn't really do anything. I have verified that the butterflies are opening all the way. I'm just trying to avoid tearing the carbs apart. Plan is to try some Seafoam and if that doesn't work, I'll have to tear them down. Tiny parts and old eyes don't usually go together.
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redfisher said:
Pushing the throttle further with no response is exactly what was happening to me.....Sounds like its staving for gas. Fuel lines and a fuel pump are cheap, if the motor has never had a carb service it due anyways, especially if it has been sitting.
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As much as I'd like to say I did it all by myself, I fear I'm going to have to pay someone to rebuild the carbs. I can do the fuel lines but will let them do that while they are at it.
 
Perhaps call your local shop and get an idea of what they will charge you for 3 kits , plus labor.----You might be shocked.-------You will even be more disappointed if that does not fix the problem with your motor !!
 
racerone said:
Perhaps call your local shop and get an idea of what they will charge you for 3 kits , plus labor.----You might be shocked.-------You will even be more disappointed if that does not fix the problem with your motor !!
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Yes, I would. I just don't see what else it could be I've replaced every single part on the ignitions side except for the stator under the flywheel. It just runs too smooth to be something serious (I think and hope). Another question for you, I would like to add a tell tale and possibly a temp gauge. Can I just pull the thermostat housing then drill and tap it for a 1/4 NPT the hook a T to it? One side for the pee hose and the other for the temp sensor? It's about as high as you can get on the engine so I assumed there would be the best spot, plus I can take it off pretty easily so I don't have to worry about getting bad stuff inside the engine.
 
redfisher said:
Have you at least checked the fuel filter ?
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Yes, guess I should have listed all that I've done so far. New fuel filter and pump. Replaced fuel line from tank to motor and primer bulb as well. Cleaned carbs while on the boat with carb cleaner but in hindsight it probably didn't do much. I'm taking it out next Wednesday and will run a double dose of Seafoam through it with my fingers crossed. If that doesn't work, or at least help, I'll be calling the local repair shop. I'm guessing that boat with that motor should take 2-3 seconds to get up on plane. Does that sound right?
 
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