Johnson Seahorse 18HP cutting out

[johnflash]

Hopefully someone may have experience or insight into this problem. We have a Johnson Seahorse 18HP Model FD14B (year 1960 ?) thats starts good, and runs just fine but every 10-15 sec while under power it will cut out momentarily (fraction of a second) and then continue to run fine until the next time. Any ideas on what to check ? Thanks in advance....

 

[david_r]

Re: Johnson Seahorse 18HP cutting out

do you have a water/fuel filter?

have you changed the fuel lines?..........new ethanol gas is causing lots of problesm.......... you can look in tashasdaddy's secret file for info....

is it a sneeze or a miss like it quits then picks back up?

 

[splitshot]

Re: Johnson Seahorse 18HP cutting out

sounds like spark maybe, seems like if it was fuel it wouldnt run good at all...if you have a timming light next time you go out, put it on each plug wire (when its acting up) and if there is a difference in the light on one cylinder thats a start to figuring it out, there are many other test you can try just search on here for them

does it do the same at idle ?? does your have the fuel pump or the old pressurized fuel tank ??

 

[johnflash]

Re: Johnson Seahorse 18HP cutting out

Thanks for the replies. Unsure if filter exists or was changed - i'll check next time i get to where the boat is 9father in law got motor ready). The problem does not occur at idle, only while under power and yes it is more like a hiccup - every 10-15 seconds... (hmmm.... how long would it take for the float bowl to empty .. if the float/valve wasn't working properly?)

 

[jdsgrog]

Re: Johnson Seahorse 18HP cutting out

Have you adjusted the high speed needle valve? There could be a possibility that your coil may be bad as well. It may be cutting out. If you haven't already, check for spark and compression (spark should be blue and thick over a gap of 1/4 inch). Did you check for gap on the points and make sure they are clean? Carbs may also need to be cleaned and rebuilt. My best bet is that you are either running too lean or you may have a bad coil or the points are not gapped properly.

 

[tx1961whaler]

Re: Johnson Seahorse 18HP cutting out

Try the carb adjustment:
http://forums.iboats.com/showthread.php?t=167352

 

[samo_ott]

Re: Johnson Seahorse 18HP cutting out

Sounds like ignition related to me. If you can, post a video of it running at speed and it would help a lot...

 

[old boat 54]

Re: Johnson Seahorse 18HP cutting out

Johnflash,
I was wondering if you solved your problem. I have the same issue recently on a 1966 33 hp seahorse. Idle is ok, but any kind of loading on motor, (meaning higher rpms) I get what feels like a brief cut-out. It almost feels like you bumped something in water. In other post people have mentioned cluth dog, but that also has a bang associated with it, and I dont think that is the problem. My Brother and I think it ignition related.
Mine is random, apporx 20-30 seconds, but in no particular pattern. I just returned from vacation and am going to go through the motor with basics. once I located cause, I will reply hear, in case you did not solve your problem yet.
Happy boating

 

[tx1961whaler]

Re: Johnson Seahorse 18HP cutting out

Johnflash,
I was wondering if you solved your problem. I have the same issue recently on a 1966 33 hp seahorse. Idle is ok, but any kind of loading on motor, (meaning higher rpms) I get what feels like a brief cut-out. It almost feels like you bumped something in water. In other post people have mentioned cluth dog, but that also has a bang associated with it, and I dont think that is the problem. My Brother and I think it ignition related.
Mine is random, apporx 20-30 seconds, but in no particular pattern. I just returned from vacation and am going to go through the motor with basics. once I located cause, I will reply hear, in case you did not solve your problem yet.
Happy boating

I had a similar issue on one of my 40's that drove me nuts for over a year. That problem ended up being a slightly defective vacuum cut-out switch that would occasionally cut out one of the cylinders.

 

[old boat 54]

Re: Johnson Seahorse 18HP cutting out

I had a similar issue on one of my 40's that drove me nuts for over a year. That problem ended up being a slightly defective vacuum cut-out switch that would occasionally cut out one of the cylinders.

tx1961whaler,
Thanks for the reply. Actually, I forgot about that. I did notice that the hold down nut on one of the wires was not tight, so I tighten it down, while thinking, I should remove the switch, and see if the internals are in good shape, but I did not do that yet. Thanks for the reminder. I did recieve my manuals, and was reading how it is used to cut out lower cylinder to keep crank case pressure form getting to high on idle.

 

[lindy46]

Re: Johnson Seahorse 18HP cutting out

I had a similar issue on one of my 40's that drove me nuts for over a year. That problem ended up being a slightly defective vacuum cut-out switch that would occasionally cut out one of the cylinders.

Just disconnect and tape off the wire (so it doesn't ground out) from the center of the cut-out switch. If problem goes away, it's the switch.

 

[johnflash]

Re: Johnson Seahorse 18HP cutting out

Had been off this site for awhile and realized I never closed this. The cause of this problem, the cutting out under drive speed, was surprisingly a worn gear. I don't know enough about the drive train to identify which one but our local marina found the teeth of one side to be worn enough so that, under load, it gradually slipped out, then re-engaged until the next time it gradually slipped apart. At idle the gears apparently stayed meshed. The solution was a pleasant surprise - the gear was such that it could be reversed - so that in forward gear it is now using the side of the teeth former used for running in reverse - and the problem was solved. The problem has never shown up while running in reverse since that is pretty much idle speed anyways. That marina saved me a bundle - it has kept my business !

 

[HighTrim]

Re: Johnson Seahorse 18HP cutting out

Lol, while reading through this I was thinking sounds like a clutch dog to me. Then I realized how old the thread was! Thanks for posting the problem though, good to see things resolved.

 

[F_R]

Re: Johnson Seahorse 18HP cutting out

LOL, Me too. Yeah, as I was reading it I said right away it is a worn out clutch dog and/or forward gear. It is coming out of gear, rotating 1/2 revolution and slamming back into gear---till next time. Outboard mechanics hear the same old story all the time. People usually say it feels like you hit a log (or here in FL, a gator).

Now all you guys with the same symptoms can read this and put this thread back to bed, please. And start a new thread if you have more questions.