78' 35HP Johnson Starting/Running Saga

[mnsherick]

Re: 78' 35HP Johnson Starting/Running Saga

You likely do have fuel issues. Could be a clogged carburetor. But you definitely have a compression problem. Your fuel pump runs off the compression in the top cylinder of that motor. If you have low compression, it will not pump as efficiently and result in what you are experiencing. Scanning the posts from the experts that have responded here, I believe the consensus is to pull the head off and see what the cylinders look like. This could be as simple as a blown head gasket which is a fairly easy repair. You can post pictures of the cylinders and the experts here will let you know.

Thanks for all the advice...I'll get the pics posted as soon as I can.

-Matt

 

[rodbolt]

Re: 78' 35HP Johnson Starting/Running Saga

your blown head gasket is a symptom not a cause.
pull the head and carefully inspect the cylinder walls for scoring. if any scoring is evident wipe a penny acrossed the score lines. if it leaves any copper behind the cylinder is unfit for further service and must be repaired.
carefully check the cyl head surface for flatness.
.004 is max warpage allowed from end to end,
normal cause for the described failure is a failing cooling system.
cylinders are siamesed on that engine and dont tolerate overheats. that engine normally wasnt originally equipped with an overheat alarm but it can be added.
also check the water deflectors in the block for damage or swelling and inpsect the thermostat assy.

 

[bream master]

Re: 78' 35HP Johnson Starting/Running Saga

I have the same engine as yours 35el78r,i can tell u right now your compression readings r low very low as aposed to what mine read which r 135psi in both pots,check your head gaskit,thermo stat,as well as blocked hoses or pin holes,and make sure you check carby again and set jet to 1 and 1/4 turns from closed position.Oh just to mention check fuel pump as well.........HOPE THIS HELPS

 

[mnsherick]

Re: 78' 35HP Johnson Starting/Running Saga

Ok first let me apoligize for the poor pictures, I had to use my camera phone. I took a bunch of really good pics with my 10MP camera, and then found out my USB ports are no longer working on my PC 1 more thing to fix!

I'm no expert but the head gasket looks blown! I've got a call into the shop to locate a new one, I don't know the age of this one but...

1) What would cause this type of failure
2) What else should I check before re-assembly
3) Any pointers/tips you can give me for this repair

thanks in advance again

-Matt

 

[bream master]

Re: 78' 35HP Johnson Starting/Running Saga

.The procedure for doing this is relatively easy,first make sure head is clean for when u buy new gaskit,and check for warpage by running a straight edge across the top,also replace water deflectors and thermo stat.Torque settings should b 18 to 20ft pounds no more,start with low torque then gradually increse till u reach 18 to 20ft pounds.One of the reasons for failure cld b to rich or to lean,incorrect mixing ratios,overheating due to water pump failure etc etc.On my engine i use BP UTIMATE fuel at 98 octane together with PENRITE fully synthetic two stroke outboard oil,i can tell you she pulls my 4meter quintrex with ease,and my engine perfoms floorlesly.If you take care of her she will take care of you for many years to come.........CHEERS

 

[rodbolt]

Re: 78' 35HP Johnson Starting/Running Saga

I already told and Ill tell ya again.
you overheated the engine and warped the head and popped a head gasket.
its just that simple.
carefully inspect the cylinder walls for scoring like I posted above.
carefully check, then surface the cyl head.
then go find if the t stat and water pump impeller and associated impeller parts are servicable.
when you hear the phrase"siamesed cylinders" refer to the second pic and notice there are NO cooling water passages BETWEEN the cylinders.
thats whats known as siamesed.
its also an open deck as there are no supports between the BLOCK and the cylinder DECK. so you have an open deck siamesed cylinder design that simply wont tolerate overheat.
dont chase fuel issues go find your cooling system failure after you fix the damage it caused.
trust me.
just looking at the pics the water deflectors look ok but I dont like the scoring of the top cylinder but I am looking at pics your looking at the damage so check it with a penny like I posted.

 

[mnsherick]

Re: 78' 35HP Johnson Starting/Running Saga

I already told and Ill tell ya again.
you overheated the engine and warped the head and popped a head gasket.
its just that simple.
carefully inspect the cylinder walls for scoring like I posted above.
carefully check, then surface the cyl head.
then go find if the t stat and water pump impeller and associated impeller parts are servicable.
when you hear the phrase"siamesed cylinders" refer to the second pic and notice there are NO cooling water passages BETWEEN the cylinders.
thats whats known as siamesed.
its also an open deck as there are no supports between the BLOCK and the cylinder DECK. so you have an open deck siamesed cylinder design that simply wont tolerate overheat.
dont chase fuel issues go find your cooling system failure after you fix the damage it caused.
trust me.
just looking at the pics the water deflectors look ok but I dont like the scoring of the top cylinder but I am looking at pics your looking at the damage so check it with a penny like I posted.

Firstly....I recently acquired this boat I've only owned it a month, first thing I did before I took it out was replace the impeller and changed the lower unit oil, so 'I' never overheated it, but I don't doubt 'someone' did at some point. That's just what you get when you buy something used these days...

I get good water flow through indicator port, as well as discharge from exhaust outlets.

How would I check T-stat...boil in water until certain# degrees and see if it opens like checking T-stat on a car?

What temps are acceptable for this engine and where would you take readings?

Penny leaves no copper in cyl walls so I'm assuming ok?

Is there something to look for when checking water deflectors they just look like water tubes?

-Matt

 

[bream master]

Re: 78' 35HP Johnson Starting/Running Saga

Check the stat like u said in boiling water,you will c it opening.As for temperature readings i dont really no.Place engine on muffs and the water coming out of pee-hole should b cold not hot,also place your hand on the exhaust plate or cylinder head for around 5to6 seconds,it should not burn you at all,it should b warm to the touch.As for water deflectors,3/8 hose cut to size and your job is done.Also just to mention if you have a steady constant stream coming out of pee-hole,that wld tell u there is nothing wrong with the impeller..........CHEERS

 

[kenmyfam]

Re: 78' 35HP Johnson Starting/Running Saga

Check the stat like u said in boiling water,you will c it opening.As for temperature readings i dont really no.Place engine on muffs and the water coming out of pee-hole should b cold not hot,also place your hand on the exhaust plate or cylinder head for around 5to6 seconds,it should not burn you at all,it should b warm to the touch.As for water deflectors,3/8 hose cut to size and your job is done.Also just to mention if you have a steady constant stream coming out of pee-hole,that wld tell u there is nothing wrong with the impeller..........CHEERS

Stat should open at around 140 degrees F and be completely open at 160 degrees F.
Meat thermometer, stat in a glass bowl and addhot and cold water as required until it gets to the 140 degree mark. Watch from there.

 

[mnsherick]

Re: 78' 35HP Johnson Starting/Running Saga

Check the stat like u said in boiling water,you will c it opening.As for temperature readings i dont really no.Place engine on muffs and the water coming out of pee-hole should b cold not hot,also place your hand on the exhaust plate or cylinder head for around 5to6 seconds,it should not burn you at all,it should b warm to the touch.As for water deflectors,3/8 hose cut to size and your job is done.Also just to mention if you have a steady constant stream coming out of pee-hole,that wld tell u there is nothing wrong with the impeller..........CHEERS

Thanks

I've checked the pee-hole it starts up with 'warm' water after 3-5 mins cools right down (this is why I thought the cooling system was working)

I've also placed my hand on the cyl head and it's not too 'hot' to the touch can easily hold my hand on it, these where the only tests that I knew to do.

I will check t-stat before I put everything back together, will report when it's back up and running.

-Matt

 

[bream master]

Re: 78' 35HP Johnson Starting/Running Saga

Three to five mins doesn't sound right to me,it doesnt take that long for water to circulate threw a hose before it gets cold,the exhaust ports should b warmish due to exhaust emissions,but the pee-hole water,should b cold.I am thinking that when u do the rebiuld you will most definately change the thermo- stat anyway.Dont use any after market stuff,stick with original BRP or OMC products............CHEERS

 

[rodbolt]

Re: 78' 35HP Johnson Starting/Running Saga

by your description it was heating up, the drag marks on your cyl pics prove it.
why it was heating up you have to find as I am at a keyboard.
as it heats past its design paremeters the piston skirts start expanding further than designed and start dragging on the cyl walls.
this will continue,even though power is going down, until the engine simply locks up and quits or a head gasket blows and dumps compression to a level low enough the engine cannot run.
should not have warm water at the pee hole at any time.
could have a restriction anywhere between the pump and the tell tale or the pump could be sucking air at planing speeds.
dunno
I am just telling you why the head gasket popped based on your description and pictures.

 

[mnsherick]

Re: 78' 35HP Johnson Starting/Running Saga

by your description it was heating up, the drag marks on your cyl pics prove it.
why it was heating up you have to find as I am at a keyboard.
as it heats past its design paremeters the piston skirts start expanding further than designed and start dragging on the cyl walls.
.

So what are the acceptable temps, and where do you take the readings?

-matt

 

[psteurer]

Re: 78' 35HP Johnson Starting/Running Saga

Not to derail the need to test for an overheating problem, but I want to go back to something said in an earlier post by mnsherick. The post said that the motor was new to him and that the first thing done was to replace the impeller. Now assuming that was done correctly, it is possible that the overheating damage was done by the previous owner and it just got worse by the new owner running the motor.

So you want to make sure that your engine is now cooling properly after you replace the head gasket. The posts by the experts here say to:
-test Thermostat (Stat should open at around 140 degrees F and be completely open at 160 degrees F. Meat thermometer, stat in a glass bowl and addhot and cold water as required until it gets to the 140 degree mark. Watch from there.)

-test the cylinder block. mnsherick said he put his hand on it and said it was not hot to touch. There are temperature sticks do this more accurately but I am not sure if that is necessary. Once you get the motor back together, why don't you give it a couple of minutes run at WOT. Keep the engine running and remove the cover and give it a feel again. It should not be hot to the touch. If it is hot, then you could have a problem in the water pump or an obstruction as said earlier (could have a restriction anywhere between the pump and the tell tale or the pump could be sucking air at planing speeds.)

 

[mnsherick]

Re: 78' 35HP Johnson Starting/Running Saga

UPDATE:


1) Replaced head gasket
2) Replaced T-stat & gasket (old one was stuck open, might account for rough idle at times)
3) Replaced water-jacket gasket

Compression test shows:

125/TOP
120/Bottom

Reset carb to 1 1/4 turns, engine starts on first attempt.

I still haven't checked WOT, or double checked cooling system (waiting on my dad to get here for some help)

Will report back with findings on cooling system, and performance.

-Matt

 

[rodbolt]

Re: 78' 35HP Johnson Starting/Running Saga

did you carefully check the cyl head for warpage? that design was notorious for warping heads when it overheats.
if its warped more than about .004 you can expect head gasket failures.

 

[mnsherick]

Re: 78' 35HP Johnson Starting/Running Saga

did you carefully check the cyl head for warpage? that design was notorious for warping heads when it overheats.
if its warped more than about .004 you can expect head gasket failures.

Yes, was off about .001 did the old, sand paper/glass trick and flattened her right out, I think the head gasket problem was the old boy I bought it from always mixed 100:1 and ran fuel mixture darn rich as well. With the T-stat 'stuck' open and good water flow I don't think temps was the problem, however I'm going to double check in a little bit.

-Matt

 

[rodbolt]

Re: 78' 35HP Johnson Starting/Running Saga

cool
when in good shape those were decent motors.
100 to 1 is acceptable however 50 to 1 works just as well and gives a margin of safty in case of cooling or fuel system degradation.

 

[bktheking]

Re: 78' 35HP Johnson Starting/Running Saga

cool
when in good shape those were decent motors.
100 to 1 is acceptable however 50 to 1 works just as well and gives a margin of safty in case of cooling or fuel system degradation.

Acceptable for trolling, high speed running forget it, 50:1.

Even OMC recalled 100:1 on the 9.9's and said to run 50:1, just not worth the risk.

 

[bream master]

Re: 78' 35HP Johnson Starting/Running Saga

Everything sounds good mate,your compression readings are starting to sound more like it,just to mention you might want to start using synthetic two stroke oil, the extra protection it gives your motor is totally worth it.Also after your first run out make sure you re-torque the head bolts.......CHEERS