76 15 johnson seahorse, runs rough, wont idle

[big catfish]

Hi all, great board! I jsut got a new motor(used) with a new powerhead. Did a compression test, 117 in the top barrell, 112 in the other. I ordered a carb kit, new coils, points, condensors, and a gasket kit, and replaced the tank and bulb, lines etc. My question is, is there a timing adjustment on this motor, '76 johnson seahorse, 15 h.p.? I would at least like to check it, as I have no idea about the previous owners mechanical aptitude. Also, any tips on installing the above mentioned parts, and is this a motor known for anything, good or bad? Anyhow, thanks for the help and the board! John

 

[big catfish]

Re: 76 15 johnson seahorse, runs rough, wont idle

Already got another question. When I twist the throttle with the cowl off, I notice that I am already in the almost full throttle position before the cam under the flywheel makes contact with the roller on the carberator. I can take my finger and give it more throttle and the engine speeds up, but I am maxed out on the twist grip, is there an adjustment? I was thinking of just wrapping some tape or something on the roller to take up the slack, but that is kind of hokey, any tips? Thanks again, John

 

[petryshyn]

Re: 76 15 johnson seahorse, runs rough, wont idle

Yo big catfish <br /><br />If I remember right, set the point gap to .020 <br />There should be a mark on the cam which lines up with the cam follower when the cam follower just mates with the cam. The throttle link should just touch the cam at this mark. It is adjusted by loosening the 2 screws that hold the cam and pivoting it in and out. If I remember right, the follower touches the cam some where around the mid point. Thats all there is to timing.....<br /><br />good luck!

 

[JB]

Re: 76 15 johnson seahorse, runs rough, wont idle

Howdy, Catfish. Your best bet is to get a manual which will give you step by step linkage adjustment and synchronization (link 'n' synch).<br /><br />Schematic describes the essentials exactly as I remember them, but I don't have a manual that goes up to '76.<br /><br />One thing I am sure of (well, 2 things). You should be able to open the throttle plates 100% with the tiller grip if it is in gear, and the mag timing should start tracking with the throttle as you come off idle. From your description, neither is correct.<br /><br />Get a manual, even if it's just a library loan.<br /><br />Red sky at night. . .<br />JB

 

[Waco]

Re: 76 15 johnson seahorse, runs rough, wont idle

Big Cat, have you tested this yet? I have a simular motor, and I was wondering what your results were? Were you able to adjust the throttle plates to open 100% with the twist grip?

 

[G DANE]

Re: 76 15 johnson seahorse, runs rough, wont idle

Hi big catfish:<br /><br />You can adjust it in the following way: turning the throttle makes the armature plate moving. Do it slowly from iddle position with engine shut off and in forward gear. Look at the butterfly axle at carb. The carb axle must NOT start mooving before the roller is between or a bit longer than the two marks on armature plate. If it does, it will caluse bad backfire ! When done. advance to full throttle and check if carb openes full. Adjustment of start opening is done by adjusting length of connection arm between roller lever and carb. Full throttle usually is ok when first adjustment is in order, but if insufficient, the cam can be adjusted as mentioned in above post. Some cams however are fixed, and you the have to play a bit with length of arm.

 

[G DANE]

Re: 76 15 johnson seahorse, runs rough, wont idle

Hi again:<br /><br />The 15HP has no specific ignition timing adjusting feature, only this timing- to - throttle adjusting. Ignition timing is ok, when points are set exactly 0.020.<br /><br />Not very difficult to work with.<br />Good luck