1974 Johnson seahorse 4hp weedless running strong, then randomly dies out and takes a lot to start.

[B_assmaster74]

I just recently purchased a 1974 Johnson seahorse 4hp weedless. After getting it out on the water, it was really hard to start, but when I got it started , it ran strong for about 20 minutes. Then it stalled and sometimes it would start 5 pulls it just 1. It wouldn’t run for long. We took it back to the guy I bought it from and he tried it and it ran but then died out and wouldn’t start. He gave me my money back, but then called and told me he got it running on his tank. So I bought it back because he said we bought gas which could have been possible because we had to go to the pumps two times because the first time, we only got .7 litres in 15 min and we only have a 3 gallon tank and filled it to about halfway. I bought it back and it started 2nd pull. Right as we went to dock we went we under this bridge that appeared to have more gunk than anywhere else. The engine suddenly sounded different and then 30 seconds later, it stalled and it wouldn’t start. Any ideas on what’s going on? It has good compression and good spark. Could it be the impeller?thanks

 

[racerone]

Good spark means spark that will jump a gap of 1/4" or more on a test device.-----When you buy a motor it is a good idea to install a new impeller.----And to grease driveshaft spines.-----Pull the flywheel and have a look at the coils.

 

[B_assmaster74]

Would the impeller cause it to not start? Also the vent is seized on my tank but it starts without it.

 

[B_assmaster74]

Good spark means spark that will jump a gap of 1/4" or more on a test device.-----When you buy a motor it is a good idea to install a new impeller.----And to grease driveshaft spines.-----Pull the flywheel and have a look at the coils.

The person we boat it from did all that other than the coils

 

[racerone]

I suggest you take it back.----It would be a simple fix for an expert.

 

[B_assmaster74]

We did that and it started and ran great with his tank. Wondering if I it could be my tank?

 

[B_assmaster74]

I suggest you take it back.----It would be a simple fix for an expert.

Could it be my tank?

 

[racerone]

Good luck with your motor.

 

[B_assmaster74]

Good luck with your motor.

So its not the tank?

 

[racerone]

You do some trouble shooting or take it back to the seller to help you.-----It would be an easy fix for me !!

 

[B_assmaster74]

You do some trouble shooting or take it back to the seller to help you.-----It would be an easy fix for me !!

it works at his place, but it doesn’t when we try it

 

[airshot]

We did that and it started and ran great with his tank. Wondering if I it could be my tank?

Sorta answered your own question....

 

[saltchuckmatt]

Would the impeller cause it to not start? Also the vent is seized on my tank but it starts without it.

Yes, it can be your tank. It needs a vent to continue to run.

 

[tphoyt]

If tank doesn’t vent it will not provide fuel.
It will become vacuum locked.
If you cant get the vent open then open the cap a bit and see what happens.