Johnson V8 275 '88, some problems

[levi_tsk]

Re: Johnson V8 275 '88, some problems

no its not lol not with a V8 for sure and if the cav plate is 2-3 inches below the bottom of the hull id expect to gain several mph by making it even with the bottom

and yes its perferable to use a bracket because with the set back you can go a little higher than the bottom of the hull - gaining a little more speed

you could see about a 19" pitch four blade stainless cupped prop this would let you run even higher and a little faster too ( i say 19" because when you switch from 3 - 4 blades youll loose 200 rpm and youll make that up by loosing an inch of pitch )

 

[fdahl_009]

Re: Johnson V8 275 '88, some problems

Ok, progress..

I installed an 6" setback bobs machine lift.
Cavitation plate was 3" below bottom before, now it is the same with the lift at the lowest position, but at 6" rised, 3" above bottom of boat it seems to be just like it is floating on top of the water, and has an occasional propeller slip, especially when going into plane.

It felt much better so I installed the 26p prop again, and guess what, no change.
It did not help to raise it, at least not in top speed. But it does not dig in as much as before.

Today I did an timing check and it was ~20 degrees at max. I was not able to get any more than ~23-24 degrees out of it, I adjusted the stop alot, not sure why it sort of maxed out there.... The markings on the flywheel goes to 28, so I had hoped that it would be in that area when adjusted as max of what is possible.

Now, new data for the 26p WOT;
Old ~20 degree timing, 4600rpm 46.3knots 53.44mph Raker 14.5x26
New ~23-24 timing, 5300rpm 54.53knots 62.76mph

Anyone know what max timing that should be on this engine?
It is getting 95 or 98 octane fuel. Regular pump gas here in Norway.

 

[fdahl_009]

Re: Johnson V8 275 '88, some problems

Bump..

Anyone know what the max timing advance for this engine should be?

 

[dehydrated]

Re: Johnson V8 275 '88, some problems

16degree +-1 btdc

 

[fdahl_009]

Re: Johnson V8 275 '88, some problems

Ah, so low?
It was around 20, I thought that was too low, so I adjusted it up to ~24 and felt an performance gain.
Will set it to 16 and see what happens, but I am afraid that it will loose much of its power..

 

[dehydrated]

Re: Johnson V8 275 '88, some problems

the numbers 16 dergree was off 1989 v8 so 1988 could be differant my v6 is 18 degrees deffinitly dont want to go too far advanced

 

[fdahl_009]

Re: Johnson V8 275 '88, some problems

Well, did some testing today. I felt an performance loss when going onto plane at 16 deg, so I put it back to 20 like it was when I bought it.

After running for a while today, I filled up about half the tank, since it was nearly empty, then the engine suddenly started to behave a bit strange. It feels a bit like it sometimes do not get fuel, like it runs out.
You can start to go into plane, wot, the engine has nearly no power, than suddenly it pulls real hard, then kind of dies again etc.. Sometimes this happens when you are already on plane, so we drove back on idle rpm with the gear engaged.

One thing that caught my attention when I took the cover off during the trip back was that the lower of the two vro pumps seems to make an really "hard" clicking sound that I am not sure I have heard before. The upper of the two clicks once every other second or so, but the lower constantly clicks, sounds a bit like poorly adjusted valve clearances on an 4stroke car engine. It follows the engine rpm, at least one to two times it clicks per second at 800-1000rpm idle. The upper of the two varies at idle, but not easy to hear so I need to touch it to feel what it does..

Is this the time to change or ditch the vro system?
Since this happened after I did a refill of the tank, how much oil do you need to have mixed in the gas for the engine to not be able to run on that fuel?

 

[dehydrated]

Re: Johnson V8 275 '88, some problems

if you get rid of vro mix 50to 1 13.oz per 5 gal fuel

 

[fdahl_009]

Re: Johnson V8 275 '88, some problems

The clicking sound from the pumps started because there were small holes in the fuel hose, so it were not able to suck fuel from the tank the way it should.

After replacing the hose it did not run good at all, did an complete clean of all the carbs. But it did not perform as it should at all, it did not feel as crisp as before, and less rpm at wot.

Today I installed new plugs, QL82YC instead of the QL78YC which was in the engine before. The old plugs have probably been soaked with oil when the fuel pumps failed to get fuel.
New plugs and hose and everything seems to be back to normal again. Much crisper onto plane again.

It may just have been the old plugs, but yesterday when testing the ignition advance, I did get heavily pinging from the engine under acceleration with ~16-18 advance, so I just backed the throttle as soon as I heard it. When running 20-21degs it pulls harder and no pinging. I would have thought that the high advance would be nearer to ping than low advance, but it definitively where the other way around yesterday.

Maybe it had to do with the old plugs, will try again with the new plugs at the next possible occasion.

 

[fdahl_009]

Re: Johnson V8 275 '88, some problems

When looking into the carburetors from the airbox, should the throttle plates move to exactly 90deg, as to my eyes it looks like they then create the less air restriction and biggest area for air to move through. They where moving a bit past 90deg, so it seems to me like they restrict the flow a bit again, what is the correct setup/setting?

 

[mrv8outboard]

Re: Johnson V8 275 '88, some problems

I would not remove the VRO's. You need to make sure the fuel system in the boat is appropriate to feed a V8 outboard. Never have a primer bulb. OMC had a primer pump with a by pass loop and these work well. Start at you tank siphon tube and make sure there are no screens in it as well as it should have a minimum of 3/8" ID. Your whole fuel system is to be a minimum of 3/8". I use 1/2" ID fuel line to the stern rigging area, into the OMC water separating fuel filter bracket ( it has larger pipe thread ports) into the primer pump. Then step it down to 3/8" ID the short run to the motor. Fuel starvation is the number one issue that is blamed on the VRO system. I run the VRO pumps on my offshore race boat. I do premix and have the oil side blocked off on the one I run now, ( but for ability of changing the oil ratio) my two previous boats used the oil injection as well. I won a world championship in one of the boats using the VRO. To date (since 1990) I have not had a powerhead failures on any of my personal or customers engines,(knock on wood).

You would benefit from a 20" midsection as the center of gravity moves up quickly when you raise these motors.

If you are skiing with this you want to prop it just about on the rev limiter.

Also do a jet check. At WOT kill the ignition keeping the throttle open, then pull your plugs and read them to make sure you are leaning it out. Advancing the timing will do this. Good luck and enjoy your ride.

 

[fdahl_009]

Re: Johnson V8 275 '88, some problems

Thank you for an informative answer.
I did run an holley blue electric fuel pump to make sure that it do get enough fuel on top. No difference. So the pumps seem to give enough pressure and volume.

I have welded an 1/2" ID pickup tube in the tank (custom steel tank in the boat), run 1/2" inner diameter tubing all the way from the tank to the plastic "f" split for the fuel pumps on the engine. No primer pump.
It starts almost every time just from the fuel in the carburetors, then it starts sucking from the tank, so I am surprised that I do not get more of an problem without the pump.
It seems to me that the VRO is working as it should now, I have had an two hour trip with an friend today, skiing wakeboarding etc, not a single miss. Burned about 13-14 gallons of fuel.

 

[mrv8outboard]

Re: Johnson V8 275 '88, some problems

Keep an eye on the flywheel magnets. The high hat flywheels are prone to the magnets coming loose. I have also seen it on the low profiles as well.