79el70 lack of power when in gear issues

[PSL]

I have a 1979 Johnson 70hp w/ single lever controls I picked up the other day that is having some issues. I went to look at the motor, heard it run ,tested the shifter for proper shifting/movement etc etc, all seemed fine. Motor was mated to a 16 foot K&C Deep V (max rated for 90hp). Had it on the lake today for the first time to test things out. Started engine with no problems and let it warm up (using warmup/start lever on top). After ten minutes of ideling I headed out to open water to see what it could do. Here's the problem, when i give it full throttle it sounds as though it bogs down and only hits about 2000-2500 (rough guess) rpm in gear. However if I put it in neutral and manually move the throttle at the carbs, I get full rpm. Also, the prop spins freely in neutral and you can feel the compression when you spin it in gear. No grinding or any other indication of obvious damage.<br /><br />Any thoughts?<br /><br />One quick related question- is it possible I hooked up the 2 control cables backwards? I don't think it is but I could be wrong!<br /><br />Links to photos of motor and controls for reference<br /><br /> MOTOR <br /><br /> MOTOR 2 <br /><br /> CONTROLS

 

[voodoo]

Re: 79el70 lack of power when in gear issues

Linky no worky.<br />Clean carbs, do link n sync.

 

[PSL]

Re: 79el70 lack of power when in gear issues

Link and sync? Guess I forgot to mention I am new to the boating world (well , atleast owning and maintaing one). Could you be a little more specific please.

 

[alden135]

Re: 79el70 lack of power when in gear issues

Originally posted by PSL:<br /> Link and sync? Guess I forgot to mention I am new to the boating world (well , atleast owning and maintaing one). Could you be a little more specific please.

Your first purchase should be a manual. Get one at marineengine.com. The link/sync is a procedure where you set the linkage for the carbs/timing/etc. You need the book to do it.

 

[Seasport]

Re: 79el70 lack of power when in gear issues

Hi PSL - definitely not a good idea to rev the motor to full revs in neutral. You're likely to blow it up. I agree re the service manual. You'll need that first if you are going to work on your motor. Lots of experts here who can offer advice.<br /><br />There could be a number of things wrong. New motor to you and I presume you don't know its service history. The experts here will tell you to clean the carbs first - plenty of posts on this subject. Check the compression, spark to all cylinders, ignition timing and link and sync. Also pay to change the impellor.

 

[PSL]

Re: 79el70 lack of power when in gear issues

The manual is on it's way! As for service history , well , all I know is that the impeller was done about 4 months ago as well as plugs and a carb kit (according to the reciepts with it). I had the same sort of problem on an old motorcycle and it turned out to be a coil. Is it possible this is the same case?

 

[alden135]

Re: 79el70 lack of power when in gear issues

PSL,<br />You're essentially in the same "boat" I was in when I joined iboats, motor-wise. I'm mechanically inclined, but didn't know much about outboards. That being said, let me regurgitate some info I have learned here.<br /><br />Lack of WOT could be many things. Timer base not fully advancing, dropped cylinder, overheating, dirty/clogged carbs, any many other things. The fact that the carbs were rebuilt does not mean it was done right or fully cleaned. <br /><br />You could start searching the FAQ and search feature to get started, but I wouldn't do much till your book arrives. If you ordered a factory manual it will walk you through things. The guys here are the best and have helped me a lot.

 

[PSL]

Re: 79el70 lack of power when in gear issues

At the moment I am posting from work , just trying to get a somewhat logical plan of attack. As for the forums , I have searched and read many posts that touch on my problems , but they are wide ranging I was just looking for the most likely cause (or atleast a jump off point)<br />Anyhow , the book has arrived (found one locally!) so off to the garage to troubleshoot!

 

[ob]

Re: 79el70 lack of power when in gear issues

Make sure you're Getting fire to all three cylinders.Plug leads should jump a 7/16" gap to engine block at cranking speed.Also inspect each plug and see if any appear dry.Make sure fuel filter is clean and unrestricted.Make sure fuel tank is venting properly.Insure that there are no fuel/air leaks on fuel hoses from tank to carb inlets.That's preliminary checks.Carb linkage being out of synch with the ignition advance is also a must check.Don't rule out the possibility of fouled carb orifices even though you state above that they had kits installed.<br /><br />It would have been beneficial in ruling out a failing fuel pump had you tried squeezing the fuel primer bulb while waterchecking to see if the engine would pickup rpms.Anyhoo,you can do that if all else checks out well.Antoher check you could do though is insuring that the pulse hose from the crankcase to the fuel pump is secure at both ends and has no cracks/leaks,or crimps/restrictions.

 

[PSL]

Re: 79el70 lack of power when in gear issues

Well , taking the above list as a good "map" I looked at working from the gas tank back. It looks as though the vent on the tank had been jammed/plugged. The cap with a functional vent is now installed! However I don't have a water tank to test (as the manual and several posts warn of using "ears" for anything over idle I'll just have to wait!)with to see if this is the only factor or not. So I figure I will do the plugs and make sure the carbs are nice and clean (good thing I have lots of experince in this from owning a 4cyl honda motorcycle!) before going back up to the lake (with tools and manual in hand). As for pumping the primer bulb, it was done with the motor at half throttle to make sure fuel was getting through. No change. Any how , lots of prep work before the weekend testing. Thanks for all the input thus far!

 

[PSL]

Re: 79el70 lack of power when in gear issues

Is it Saturday yet?

 

[PSL]

Re: 79el70 lack of power when in gear issues

Well , problem solved! Turns out that when the motor was transported last (In the back of a van on its side)a piece of gasket had broken off (about the size of a match head) and had lodged itself in the fuel inlet at the bottom of the float bowl. Popped the bowl off, removed bit of gasket, reassembled, pumped the buld a few times and presto! Spent the rest of the day "fine tuning" Thanks to all who provided help!