where did the power go? 1970 6hp seahorse

[gvegas88]

I've got a 1970 6hp Johnson Seahorse that has run great until recently. I use it about 4 times a week this time of year. About 3 weeks ago I was running and stopped, but when I started to leave and it would only run 1/2 or 2/3 throttle. I came back the next day and it ran fine and had done so until today when the problem returned. There was warm weather both days, fresh gas, external tank with a tight bulb, squeezing the bulb didn't help, engine is not hot and water pump seems to be working fine. The motor is much harsher running now, harder to start and if I throttle up fast it will try to cut out or accelerate very slowly. I am going to check the fuel lines and filter now. Any ideas as to what the cause could be?

Thanks, Tyler

 

[tx1961whaler]

Re: where did the power go? 1970 6hp seahorse

Probably one of your cylinders is no longer firing. Check the spark. It will run OK on one cylinder, but will have no power. One quick way is to pull one of the plug wires when it is running. If it quits, then that's the problem. If it keeps running, then put that plug wire back on and try the other one. Wear gloves and stay away from the flywheel!
The best way to check is with a spark tester and look for at least a 1/4" fat blue spark.
I have the same motor as you, waiting for a ignition rebuild after Christmas. No spark on one cylinder; bad coil. It's getting all new ignition parts and a new impeller.....

If it's not the spark or compression, then it's time to rebuild the carb, also easily done (except for that darn recoil starter right there...)

 

[Vic.S]

Re: where did the power go? 1970 6hp seahorse

As tx1961whaler says but do check or replace the plugs first and inspect the leads.

Its a points ignition system so check the points if you dont have two good sparks, also condition of coils and condensers.

 

[gvegas88]

Re: where did the power go? 1970 6hp seahorse

sounds like a start, I'll update tomorrow.

Thanks, Tyler

 

[gvegas88]

Re: where did the power go? 1970 6hp seahorse

It seems to be firing on both cylinders, but it quit about half the time I pulled the bottom wire. When I pulled the bottom wire it would struggle and nearly quit if it hadn't already, but when it didn't die I could increase the throttle and it would continue running. Pulling the top wire it would continue to run somewhat smooth. I also noticed a long delay between when I would throttle up and when the motor would rev up. I forgot to mention that the plugs are about 4 months old. Being that I got the **** shocked out of me so I'm guessing that the plugs are getting juice. I'm not familiar with rebuilding carbs or checking the coils and condensers, so if I need to do those please elaborate.

Thanks again, Tyler

 

[Vic.S]

Re: where did the power go? 1970 6hp seahorse

It seems to be running ok on the bottom cyl but not the top.

Check that the plugs really are ok by swapping them over. If they are OK check that you really do have a good spark from each lead. If you do then the ignition is probably Ok but if not then you have to pull the flywheel and check points, (Clean and re-gap to 0.020") visually inspect coils and think about the condensers.

Coils and condensers you can check by swapping over but the coils must be accurately positioned so that the clearance from the flywheel
is correct. Therefore mark their positions accurately before removing.

If the plugs are good and you get two good sparks. Probably next most sensible step is a compression check. Assume the bottom cyl compression is Ok the top one should be similar. If significantly lower then there's problem that will need a strip down to investigate.

Buy workshop manual before going any further!

 

[gvegas88]

Re: where did the power go? 1970 6hp seahorse

I just decided to run it again and it ran fine this time with full power. What does this mean?

 

[HighTrim]

Re: where did the power go? 1970 6hp seahorse

I agree with Vic, likely that you have an ignition component on the top cylinder failing when warm. Step one would be to purchase an OEM Service Manual. Step two, troubleshoot the ignition system.

Good luck.

 

[Vic.S]

Re: where did the power go? 1970 6hp seahorse

What does this mean?

It means its going to be difficult to find out whats wrong with it I'm afraid.

Check all the things suggested, start with the plugs even if they are new and work through the ignition system easy things first most difficult last.

Check for bad connections

Is plug fouling because it needs a decarb?

I'd definitely check the points at some stage.

Probably not poor compression on one cyl.