V4 Looper Cylinder heads warming up at different rates.

[sutor623]

1995 V4 130HP looper


Got some questions about head temp differences. Starboard head takes much longer to reach operating temp at an idle. Starboard plugs also seem to be fouling and are wetter.

Compression in all 4 cylinders is 135psi. Motor runs very strong at cruise and WOT. Idles well first part of the day.

VRO disabled and fuel is pre-mixed.

I have changed the thermostats, diaphrams and gaskets on both heads. I have also swapped them back and forth but the issue doesn't seem to move.

I have ruled out ignition issues. Spark is strong on all 4 cylinders, even when the motor is good and warm.

This motor runs great, but I "believe" that the starboard head is fouling out the plugs causing a rough idle/hard start after the motor has run and then set for 30mins or so.

Sitting in the water, just after startup, the Port head climbs to 135-145 degrees in a minute or two. The motor idles for however long at this temperature. (This is with the infrared temp gun pointed right above the thermostat housing.) If I point the gun at the face of the cylinders the temp can go up to 155-160 or so, and that is where she stays.

It takes the starboard head much longer to climb up to these temps. (Maybe 5 mins or more) Once it has reached operating temperature (135-145) it seems to stay there pretty well.

Issue is as follows. Carbs have been set to 2 1/2 turns out (per factory manual). The Port side plugs are nice and dry, and brown after a long run (or and idle for that matter). The Starboard plugs are very wet and look almost fouled. I put a brand new set of plugs in, and they did the exact same thing. Then, sure enough, starting got hard again, and motor would only idle well after being warmed up very well.


I do not believe there to be water getting into the cylinders because the plugs do not have water on them. The piston heads also have a layer of carbon on them similar to the port head. They do not look "steam cleaned." I also assume head gasket is good because of good compression numbers, cold and hot.

When I first got the motor (6 months ago) the rubber diaphram in the starboard head looked like it had melted a small hole through it, so I assume that head may have overheated at some point. I also know that this motor spent much of its life at an idle.

1.) Anyone have an idea why this motor is not warming up at the same rate?

2.) Would it be okay to lean the idle jets out on the starboard side 1/4 turn and see how she does? If the temp of the heads are in fact similar during running speeds is it possible that one head just likes to run a little richer than the other?

3.) Maybe my plugs look wet and fouled because water is making its way into the cylinders, even though all the other signs point to no?

 

[sutor623]

Is it normal to have the carbs set leaner than factory starting point? How about keeping the mixture different from one head to the other?

 

[sutor623]

So I took a closer look at the relief valve springs. One of them is 1.25" long (which is what it is supposed to be) the other one is 1" long. It seems to be compressed. I think that since the spring isn't providing as much backpressure it is allowing water into the cylinder head easier (under heavy throttle).

Is it common practice to change out these relief springs when changing the thermostats? I didn't think they could go bad but obviously they can change the amount of back Force they provide after being compressed all these years.

 

[Faztbullet]

Theres your problem as the water pressure is opening t-stat/poppet......

 

[sutor623]

Theres your problem as the water pressure is opening t-stat/poppet......

Thanks fazt. Funny that I have been chasing a $2 issue this whole time...........

Now, say that I do change the springs, and the starboard head plugs still seem wetter than the port. Is it possible to have to have one entire bank's (head) slow speed needles set a little more lean to keep from fouling at idle and to help at cold idle? I guess you would treat each head like its own beast?

 

[bob johnson]

BOTH carbs could be lean on that one hot side


bob

 

[sutor623]

BOTH carbs could be lean on that one hot side


bob

Yea that could be an issue. But it would have to be running lean at WOT, in which case I would surely hope not, otherwise I have myself a ticking time bomb. I think if anything, the colder side is running rich due to the fouling and excess fuel and oil mix on the plugs and plug threads. Carbs were just cleaned and entire fuel system is in good shape.

This is a pic of the plugs on the port side, they look good, no?



Pic of plugs on the starboard side, clearly they are too wet!!! Look at how much fuel mix is on the threads...........

 

[bob johnson]

155 to 160 is not a bad temp for idleing......... you could have a slight air leak in that side to just slightly lean out your mixture.. cant explain how you could get extra oil in one side of the motor unless it was a super rich mixture...you might have two different jets in your carbs...because you backed out both sides the same...

bob

 

[sutor623]

I'm hoping it's just because the poppit valve spring on the cold side is 1/4" shorter, causing the poppit valve to open under less pressure than engineered for. I'll put some new springs in her and report back.

 

[reiddo1]

Are the float settings on the port and starboard sides set at the same height?

 

[Faztbullet]

Are those QL78YC plugs???? Are these plug readings from engine running on muffs or in water??

 

[sutor623]

Reiddo, the floats should be set the same. But, to be fair, they may be set too high. I tried to get them level with the housing while inverted, but the floats really didnt require much adjustment at all straight out of the box.

Fazt, they are the QL78's. These readings were taken after a 30 minute run at cruise (42-4500RPMs)

Also, the new plugs that this engine calls for is QL82 (which are a little hotter plug). I switched over to these plugs and they look about the same............

 

[reiddo1]

My 2000 150 hp Johnson looper has a shift interrupt switch. For some years this switch would cut power to the starboard bank and for other years to the port bank when going from forward to reverse and vice versa. I tried with no success looking up your engine to see if it had a shift interrupter switch and if it is possible that it may be intermittently knocking out your starboard bank even under full power. A long shot I know but I had to ask it.

 

[sutor623]

My 2000 150 hp Johnson looper has a shift interrupt switch. For some years this switch would cut power to the starboard bank and for other years to the port bank when going from forward to reverse and vice versa. I tried with no success looking up your engine to see if it had a shift interrupter switch and if it is possible that it may be intermittently knocking out your starboard bank even under full power. A long shot I know but I had to ask it.

Hey thanks bud. I do not believe that this motor has that feature. I am also 100% positive that I am firing on all 4 cylinders very well under throttle.

The reason that I know this is because I once had an ignition coil die on the water and the boat would only hit 3500rpms and would NOT plane out. This motor is pushing a heavy boat and if there were a major issue it wouldn't be going anywhere.
I just want to make sure she stays running strong and that I am not chancing grenading the motor running it like this.
If I have to, I will pull the carbs, throttle bodies, intake mani's, and reed boxes and replace all the gaskets. I am just not convinced that I am running lean on port. Almost positive it's rich on starboard. The only system in this motor that regulates cylinder 1 and 3 is the stator (which is now brand new) and the starboard thermostat/poppet. I think that worn out spring is allowing too much water into the cylinder head.

 

[reiddo1]

Sounds like you have eliminated all the possibilities; keep us updated when you have replaced that poppet spring. Good luck.

 

[sutor623]

Ok fellas, update. I think I am getting somewhere.............

So I ran the motor today in the water with no thermostats. The temperature stayed at 60 degrees on both heads. I was just curious to see how they would behave.

Put NEW thermostats and springs in, cranked her up, and port cylinder head hit operating temp within 2-3 minutes. Thermostat cover measured 135-140 degrees (cylinder head by spark plugs was around 155 degrees) and stayed that way for as long as I would have let it run.

Checked temp on starboard cylinder. Temp took 5-6 minutes to reach 115-120 degrees and went up and down a bit. It would NOT reach proper operating temp for as long as I would let it run.

I did cylinder drop test on #1 and barely any difference. Put it on a spark tester while running and good strong spark.

Drop test on #3 (just below #1) was more noticeable, but not by too much.

Drop test on #2 and #4 (port head) would just about kill the motor. It is apparent that these two cylinders are carrying this motor at idle.

Checked compression once warmed up, 135 across the board.


I am back on the path that water is getting into the head, mainly cylinder #1. Plugs continue to stay wetter on this side. I also noticed a small patch on the head of the cylinder where it was clean metal.


Remember, that the starboard cylinder head thermostat grommet was slightly melted when I replaced it (upon aquiring of this motor). I believe that the starboard side may have overheated at some point in its career.

Where are the possible points where water from the water jacket can enter the cylinder head on these 90degree loopers?? Obviously the head gasket is one, but are there any others? Do you guys think I should pull the head and see whats going on in there, or am I on the wrong path? Maybe I should try to re-torq the head and see how that goes?

Maybe this is as simple as a mis-casting in the thermostat area of the head and too much water flow is making its way by?

Also, what if my crankcase compression is off on cylinder one? Since 2 is looking good, I would point fingers at the bearing seal under the flywheel. But, would this prevent operating temp from climbing properly in that cylinder head?

 

[racerone]

Perhaps look into issues with the crankshaft sealing rings.-------NOT the same thing as the seal on the upper bearing housing !

 

[Faztbullet]

Don't think its water in cylinder as plug would be a lot cleaner(steam cleaned).

 

[sutor623]

Perhaps look into issues with the crankshaft sealing rings.-------NOT the same thing as the seal on the upper bearing housing !

Racer, so you are thinking it is the crankshaft sealing rings on the uppermost part of the crankshaft?

Would bad crankcase pressure be most evident at idle?

Is there anyway to check for this in short of a complete tear down?

Would bad crankcase compression cause the cylinder to operate at lower temperature?

All in all is this what must be the culprit at hand? If so this really sucks man. You check all that you can when inspecting a motor before buying(compression, spark, gearcase, etc.) find out it has hard starting when warmed up after long runs, and after hours and hours of time/research and $$ in parts, then you find this out? Man there has to be another reason why this head isn't reaching operating temp. I have a one year old. Tearing a motor down just isn't in the cards right now........

 

[sutor623]

Alright,

So I did a couple other things before I decide where to go from here. I pulled the carb from cylinder 1, checked everything (including float height) and swapped it with cylinder #2's carb. Nothing changed.

I know this is a crude test, but I did the paper over the carb throat test while at idle. It sucked the paper in very hard for all 4 cylinders. If I put my hand over the throats of the carbs a TON of fuel comes out of the venturi's. This even happens on cylinder 1 (the main cylinder that has failed the cylinder drop test.) This to me means that the engine vacuum (scavenging/crankcase compression) is doing better than perceived. I am just having a hard time believing that the crankcase sealing rings are gone on the very top of the crankshaft. Plus this motor has PLENTY of power. If I pull the #1 cylinder wire and hook it to a spark tester, the motor will not plane and will only hit 3500rpms. I KNOW that cylinder is working when Im on the go.

I let the motor idle in a bucket for 15 minutes and the starboard side FINALLY heated up to proper operating temp. But it still seems to be 20 degrees cooler than port for the first 10 minutes at idle.

I also noticed that when I pull the spark plugs from the starboard side right after running up to operating temp, it seems as if a steam comes out of the spark plug holes of cylinder 1 and 3 (more out of cyl 1). A little steam comes out of the other head when doing this, but not nearly as much.

All 4 spark plugs are reading 100 degrees (with temp gun) when pulled out of the block after a 10 minute run.

I don't know guys, since the entire head on starboard just reads much cooler, (even more towards the core of the block) the vacuum is plenty strong to pull fresh fuel into the cylinder, and possible steam is leaving the spark plug holes on that side I am thinking that some water is entering that side of the motor.

If that thermostat isnt opening, how would water make its way to the cylinder? Is there anywhere water could leak into the combustion chamber with a closed thermostat?

Should I just pull the head and take a look, or am I wasting my time? Motor is a fresh water motor so I am not afraid to break off a head bolt in the block.

Thanks for everything guys. I sure hope to figure this out. My pride is suffering pretty good right now.............