1976 johnson seahorse

[u/Roadi1120]

Been fighting with this motor on and off for a couple years, it's been in the family since at least the 80's. No one can seem to get it going right. We got it running decent 2 years ago, go back this year and it's down on power, gets a lean sneeze at idle, and dies when trying to go low speed in to dock.

• cleaned carbs
• changes fuel lines (although we fought with finding a non-leaking fitting for the tank side)
• set idle speed
• 4 new coils and plugs
• 113-115psi all cylinders

Couple things, the idle adjust screw (on the lever arm) isn't even close to the stop..ever

It needs new cables, and controller shifts fine but almost half the forward throttle is play. Getting those for next summer.

I set the idle rpm at 800rpm, once we shift the rpm just slowly falls off until the engine stalls around 600rpm, i feel once we understand why it's not holding rpm we will fix the problem.

[u/Benedlr]

Were gaskets and seals reused during the 'cleaning'? Does the link arm from the carbs to the timer base under the flywheel move smoothly from stop to stop? Did you sync and link the carbs? Throttle butterflies must move in unison or one or more cylinders can run lean or rich.

[u/Roadi1120 → u/Benedlr]

I just got a timing light, will be doing a link and sync in the spring, but I checked the manual. All reference points are lined up correctly and carbs move in sync. The link arm feels stiff but moves the whole span on the timing. That stop for the link arm to timing was sitting an inch away so I adjusted the cables so it sat on the stop then the idle rpm was too low so had to pull it back away to achieve 800rpm at idle (that seems suspect at best) then I shift to forward and rpm just starts dropping until it stalls usually 10-15 seconds.

Pulled carbs cleaned and inspected seals, they were good once I installed I sprayed for any vacuum leaks and they passed. The carbs were clean no debris or anything this is when I realized the gas lines were soft from the pump to the carb and changed it.

It's just super weird, I'm going to put a fuel gauge between the carbs and pump and see if there's a correlation.

We also were able to winterize it with no problem, it just doesn't run like it used to, down on power and the die coming into dock.

There was a moment last year when we took it out and it's like the motor woke up, it ran like a bat out of hell my father-in-law said that's how it used to feel. That was short-lived we shut it off and fired back up and it didn't repeat

[u/Benedlr → u/Roadi1120]

Did you pull the idle oriface jets on both sides of the body? Use the extension nozzle to spray thru it. There should be a fine spray from the top of the carb throat. There is also a jet in the bowl base.

The stop for max timing is set on the water at WOT. The link arm should not drag. It should move smoothly. Old dried grease or a broken ring makes it drag.

Get a fuel pump repair kit unless it's been serviced since 1976. Look for a belly in the diaphragm. If it's not taut it can't deliver volume at high speed. Hold to the sun to check for pinholes that allow raw gas back into the engine.

I'd start at 600rpms and see if it idles in gear.

[u/papadukesilver]

For the amount of time and possible money you are about to sink into a 49 year old motor you can get a much newer used one with no problems. Do you enjoy boating or wrenching. That will be your deciding factor.

[u/Roadi1120 → u/papadukesilver]

Love boating/love wrenching haha we have been looking for a used 90hp but there are so few on the market unless we buy the boat as well haha. Blows my mind I can buy a v8 crate motor for 5k but can't find a 10-year-old boat motor for less than 8 grand.

It's a camp boat we have smaller boats and only used this one to get to the islands or further fishing spots until it ran like crap. It would take a lot of parts to even come close to the price of a used motor.