89 Johnson V4 120 HP Question

rrichar1 · #1 10-22-2010, 11:52 AM

I have a 1982 Wellcraft 18 Fisherman center console with a 1989 V4 120 HP J120TLAE that had a ring job (?), new fuel pump and other stuff done to it and it runs great provided I have good clean gas. I obviously have an original fuel tank that we tried to patch but it still has a leak / contaminants in it as it has issues when I run it off that but runs fine on a portable 12 gallon tank. I will eventually replace it, hopefully this winter.

My question about the Johnson is: It runs great after it's warmed up but after coming back in and going a mile or more at no wake speed it seems to die consistently after I take it out of gear when I'm on my final approach to the dock. It always starts back up so it's not a big deal. But I'm wondering if we just need to adjust the idling again and make it faster?

And can somebody give me there opinions on this motor? It seems to have a good reputation as far as reliability and it's practically a brand new motor. But I'm used to a rice burner Nissan/Tohatsu on my other boat and that I have never had an issue with (other than carb cleaning / impeller) and it's rock solid.

steplift20 · #2 10-24-2010, 09:17 AM

i had a simular problem with my merc and it was my stator, stators do crazy things when they go bad, i would have it checked

spareparts · #3 10-24-2010, 08:28 PM

Ferm? paging Mr. Ferm?

THEFERMANATOR · #4 10-24-2010, 10:52 PM

Good engine overall if taken care of. As for the idling, start off by checking the link and sync on the carbs and timing. What is the compression on it? Should be around 140-145 if it is healthy, but anything above about 125 is acceptable. What is it idling at in gear and in neutral? You want to set it to idle at about 700 in neutral, and she should be able to hold about a 600 idle in gear without stalling. Does it still have VRO hooked up? Does it smoke alot at idle? These engines will give many years of trouble free service, but if somebody works on the carbs in it and don't know how to do plastic carbs, it will be a NIGHTMARE engine for you.

rrichar1 · #5 10-25-2010, 10:01 AM

I'll get the compression numbers but last time we checked they were fine. The motor starts fine and easy and doesn't die consistently upon start up. It just takes a few minutes to warm up. It does have the VRO still hooked up and it appears to work fine and the motor does GREAT overall, I just feel like the idling is slightly off.

Maybe the engine is still being broken in from the ring job my dad did? He pulled out the pistons and cleaned the cylinders and whatever else, I'm sorry I don't know what all he did. He did clean and maybe (rebuild) the carbs as well. For all intents and purposes this is a brand new engine I would think. We had a new fuel (oil?) pump put in at a marine service shop.

I will have to get my father to check the idling and see what it's set to and report back.

It doesn't smoke at all at idle when it's warmed up but when I first start it up it gets the usual smoke but quickly goes away.

Skools Out · #6 10-25-2010, 12:45 PM

if it is only cleaned and rings that's not new and if you put in new rings it needs to run double oil for first couple tanks of fuel they usually say first 25 hrs. we need the idle in water in gear rpm currently.