Old johnson V4 boat motor

caleb.b, Oct 21, 12:13pm
I have a late 80s 90hp Johnson V4. It runs reasonably well and once you get the throttle open out on the water, it goes great but I have issues at the boat ramp when cold (I know these two strokes are never great cold) and idling round. its got good compression across all 4 cylinders and I seem to be able to get it running nice enough on the muffs on the driveway but i plonk it in the water and its a different story. I think it would be best to find someone who knows these engines well to set the idle timing and idle speed and carb mixtures. I spend more time frustrated with it when i work on it myself. Does anyone know of anyone in the Christchurch or Canterbury area that is fluent in these engines. Because someone in the know would be able to set this one up in minutes rather than all my mucking round. The Powerboat Centre (Evinrude Dealer) wont even order me in parts as my engine is over 25 years old so that rules them out.
mechnificent, Oct 21, 12:17pm
Does it sit at the correct depth in the water ?

Is the fuel tank always at the same relative height? The engine is always on the boat is it ?

It should run much the same on muffs or in the water.
snoopy221, Oct 21, 12:20pm
Does anyone know of anyone in the Christchurch or Canterbury area that is fluent in these engines

Nope- but i do know someone in Auckland. And he might well know someone in Christchurch

http://www.westaucklandmarine.co.nz/

Edited to add sounds like it might benefit from a carb strip and clean as well as timing setting.
caleb.b, Oct 21, 12:22pm
Yes, as far as I can tell all is the same, I had spark issues with it dropping a cylinder every now and then but was traced back to a broken HT lead. always runs on 4 now. The only variable is exhaust back pressure. In the manuals they recommend setting the idle higher on the muffs as once the exhaust is submerged it increases exhaust back pressure and causes a slower idle.
mechnificent, Oct 21, 12:27pm
Yeah it was the back pressure that I was thinking of. it's the obvious thing.

Check the mount depth again, and/or adjust/compensate for it.
caleb.b, Oct 21, 12:27pm
Thanks Snoopy. Ill get in contact with them and see if they can recommend someone for me.
mechnificent, Oct 21, 12:29pm
Excess back pressure will change the idle mixture too. Adjust the mixture and speed on the water is the simplest cure.
caleb.b, Oct 21, 12:31pm
Im just not confident enough to do it myself. A boat mechanic with a tank would probably have it sorted in a matter of minutes. I might do some more reading of the manual and see what the process is like
snoopy221, Oct 21, 12:35pm
Yip Glenn has been around for years.
Don't worry about them now being a merc dealer. lol
When it comes to OMC and Chrysler and knowledge of older motors and well
**Getting it RIGHT**
Top man for sure
mechnificent, Oct 21, 12:39pm
Set the speed about right, wind a mixture screw in till the engine slows a little, back it out till the revs come up and then start to slow again, then put the setting half way between the two slowing points. Then do the second idle mixture and then adjust the idle speed last. Adjust it warm.

I'm imagining it's got a twin barrel carby, or two carbies.
caleb.b, Oct 21, 12:45pm
Yes, two separate carbs. The linkage that advances the ignition timing with the throttle is terrible on these and I struggle to get mine to return properly so "Setting" the idle timing is a pretty loose term. haha.
elect70, Oct 21, 12:47pm
Had same issue turned out to be the idle as once in gear needs to idle up or just stalled cant recall where the adjustment was but a manual should give it , . We tested ours in a a big plastic wine barrel with cutaway to sit motor in it & run on load , have a hose running into it as well, plus dont run too rich oil fuel ratio either . If you need parts get them direct from johnson USA they have the record # of every ouitboard theve made & ship parts with a day , 60% cheaper than NZ dealers
snoopy221, Oct 21, 12:48pm
The linkage that advances the ignition timing with the throttle is terrible on these

**Yip**
And THAT is where *Old Skool*
Experience REALLY REALLY comes in.
bwg11, Oct 21, 1:11pm
You will need to set the idle speed slightly higher on muffs as there is more back pressure when the leg is in the water. I recollect Powerboat Centre's workshop manager left in about 2008 and set up in Rangiora - may be worth checking out.

Try Boats.net for parts.
berg, Oct 21, 6:46pm
Test the battery. Got caught with my one. Couldn't work out why it had plenty of issues. Found out that, even though it would crank ok, the battery was failing to supply enough power to get sufficient spark. Changed the battery and all good again.
taipapaki, Oct 21, 7:45pm
vro pump did this on my 140HP. was injecting too much oil at low rpm and motor was burning the oil coulnt keep the idle stable. I disco the vro pump, use premix. runs like a nut now.
serf407, Oct 21, 7:57pm
If the previously mentioned above personnel have issues, try Wade Henshaw he does a variety of engines.
peanuts37, Oct 21, 10:22pm
That old and if 2 stroke, looking at replacing crank seals wouldn't go amiss if you can't sort mixture out.
marte, Oct 21, 11:23pm
A mate showed me how to get a chainsaw going good.
1) get the petrol fuel mix exact! He used a syringe he got from a farm store for the oil. Exact! And fresh new fuel, not mixed fuel, or two week old fuel. Brand new fuel.

2, And then he did the whole idle, full throttle, idle, run, full throttle, idle, run, full throttle, run adjustment thing. Twice.

3, brand new sparkplug and recheck the idle/run/full throttle again.

Without the bar or chain, and shook the shit out of the chainsaw too. His theory was that only two things stuffed chainsaws from running properly.
Gummed up carby/wrong oil mixture.
Bad crankcase seals.
In then time he taught me this, he got two identical chainsaws of mine, that I had picked up at different times, i was given one and the other come with some scrapmetal, as scrapmetal.
He got them both running exactly the same and they idled like sewing machines.

So, crankcase pressure? Clean carbys? Correct oil mix with new fuel?
caleb.b, Dec 15, 4:19pm
Good ideas guys but its had a new battery and its VRO System has been blanked off before my ownership so just run premix which I prefer anyway. Good idea about the crank seals if I have continue to have issues. Will try to have it looked at this week by someone more clever than me and let you know the verdict.