'73 chrysler 105 surges at WOT then loses power

[spool]

Hi guys took my boat out for the first time today,

It was a bit of a disaster, where we went there is a large 5 knot Zone, probably 500 meters from shore, so I putted along just above idle until the end of the no wash zone, I went WOT and it jumped up on a plane quick and was performing as id expect it too, after 4-5 seconds the motor started surging, so I backed off and the motor stalled, started it back up and it was unhappy but ran with a tiny bit of throttle, and came good after about a minute.

I richened up the mixtures by 1/4 turn and did a hole shot, no issues accelerating until 5-6 seconds into WOT

I limped it back to the boat Ramp and Inspected the engine, the ignition box/ignitor ?( the coil is mounted to it) was held on by 1 mount, the other two had broken off. I zip tied this to the engine making sure it wasnt grounding on the engine

Went for another test run, the boat appeared to run much better.

Exited the no wash zone and hit WOT up on a plane for about 8-9 seconds before I heard a knock from the engine, instantly I cut throttle and backed off. The motor was making a knock on idle so I killed the ignition. I got a tow to shore and inspected. It, the engine seemed very hot to touch drops of water on the cylinder head were boiling and sizzling, the tell tail was spiting out a little but but not what I'd call heaps


I havnt restarted the engine yet. Did my engine just overheat?

It's a magnapower 1057he

Any help would be awesome. I'm a little disappointed

 

[spool]

Re: '73 chrysler 105 surges at WOT then looses power

Re: '73 chrysler 105 surges at WOT then looses power

Ok, so after reading another thread i decided to check the carbys, (soft surge)

i removed the top and bottom bowl and squezed the hand pump, on the bottom carby fuel flows freely
On the top carby it barely flows at all, it makes sense that fuel would build up then when i went WOT it couldn't refill quick enough.

i will fix the carby but im just hoping the engine isnt damaged. I think the engine over heated due to leaning out (high exhaust gas tempratures)
the engine sounds normal when trying to start, the knocking is gone on crank (after it started knocking i cranked the engine and it knocked on crank)


I'll put it back together and get it running in a bucket and see how it goes i guess.

 

[spool]

Re: '73 chrysler 105 surges at WOT then looses power

Re: '73 chrysler 105 surges at WOT then looses power

Ok, removed the bowl, float and need +seat, blew through the fuel inlet and a big clump of dirt came out! Installed needle seat an float and compared to the bottom carb, identical and it gushes
Fuel now.

I'll see if it starts/ runs tomorrow and get it in the water next weekend.

 

[jerryjerry05]

Re: '73 chrysler 105 surges at WOT then looses power

Re: '73 chrysler 105 surges at WOT then looses power

Makes you wonder what and where the junk came from????The fuel pump should be inspected/ rebuilt as well as cleaning the carbs.Change any filters and any in-line connectors.The squeezie and hoses too.
Is the tank vent clogged or closed?
And YES it overheated.It can push a bit of water and still get hot.I'd pull the lower and replace the impeller.
But since you got it hot you need to do a compression test.
The carb air screws needs to be set at 1 and 1/16th out.Too much and engine damage can occur.That's the inital setting.It needs to be set in the water and in gear and RPM's at 750-800 motor warm.Once you get that done then you turn the screw in till it just starts to stutter, cough,buck or stall.The back out 1/2 turn.Do this twice.Then leave it there.
NO MORE ADJUSTING!!!

 

[spool]

Re: '73 chrysler 105 surges at WOT then looses power

Re: '73 chrysler 105 surges at WOT then looses power

Cylinder 2 is down on compression 56psi, either the rings or headgasket are leaking, my bets on the headgasket

I'll pull the head off tomorrow and inspect the gasket.

 

[spool]

Re: '73 chrysler 105 surges at WOT then looses power

Re: '73 chrysler 105 surges at WOT then looses power

Repeated Leakdown test is as follows

1=130psi
2=60psi
3=120psi
4=120psi

Pulled the head, pistons look visibly ok,
The head and gasket look ok the combustion rings are not what I'd expect to see for 60psi.

The cylinder walls are not scored.

The headbolts were NOT what I'd call tight, I'd say about 20ft/lb at the most.
There was 18x1/2" bolts and 4x11mm bolts (which did not go through the head to the block)

My Chrysler manual says the bolts should be round 240ft/lb? This can't be right... The heads would snap off. It also didnt list 1/2 head bolts, there seems to be a little pinhole in one of the pistons, all the pistons have this but it is more evident on piston 2 (see attached pictures)

Cylinder 2 is in the middle



Cylinder 2 pin hole



Cylinder 2 head surface



Engine block top cylinder 1


I was wrong about no scoring on the cylinder walls, i was just too tall to notice it at first, cylinder 2,3,4 have light (thickness) scoring on the upper part of the bore, my finger nail did not catch.


The water jacket looks a bit dodgy on this cylinder (number 2) the head may have warped and leaked the combustion chamber into the water jacket?

I heard knocking at the time which leads me to think bearing damage, I am going to pull the bottom end apart and inspect the bearings. Worst case i'll bite the bullet and rebuild it.

 

[jerryjerry05]

Re: '73 chrysler 105 surges at WOT then looses power

Re: '73 chrysler 105 surges at WOT then looses power

FYI> The tourqe is about 20# on the head.THe pin hole is supposed to be there.
The scoring you see is probably the piston slap and melting the skirt.Once you break it down you will see the damage on the sides of the piston.
And ANY damage on the piston means buy new.
More pics as you go through the process,J

 

[spool]

Re: '73 chrysler 105 surges at WOT then looses power

Re: '73 chrysler 105 surges at WOT then looses power

Thanks Jerry,

I figured as much for the pin hole, the headbolt torque and scoring anyway. hopefully i can get away with just a hone, new STD pistons, rings and bearings.
I'll know the full damage after i finish stripping the engine down.

How much can the pistons be oversized on these blocks before the block is a junker? seeing i can only find 30thou pistons id assume that?
The cylinder walls do not look very thick.

might be worth trying to find a donor block.

FYI> The tourqe is about 20# on the head.THe pin hole is supposed to be there.
The scoring you see is probably the piston slap and melting the skirt.Once you break it down you will see the damage on the sides of the piston.
And ANY damage on the piston means buy new.
More pics as you go through the process,J

 

[Frank Acampora]

Re: '73 chrysler 105 surges at WOT then looses power

Re: '73 chrysler 105 surges at WOT then looses power

The "pin hole) you mention is indeed a pin-hole. It is normal. At that point there is a pin driven through the piston to keep the rings from rotating and the open ends catching in the ports. Later pistons had pins driven in from the sides of the ring grooves about 180 degrees apart to locate ring gaps on opposite sides of the pistons.

The last photo does show light scoring and some aluminum rub-off. It is a sure bet that with 50 pounds of compression, when you remove that piston, you will find rubbed aluminum from the skirt holding the rings all the way down in their grooves, thus not sealing. If all the bores look the same, you may as well break down and rebore all cylinders otherwise, if only two look like that, you can overbore only the affected ones.

As Jerry mentioned: Head bolt torque is 240 INCH pounds or about 20 foot pounds. Either you misread or the manual was misprinted. The four 11 mm bolts are or should be 7/16 heads 1/4 X 20. If they are next to the plug holes, they function to help retain the water jacket cover. If they are indeed 11 mm, then they have been replaced at some time.

It is difficult to see from the photos, but it also looks like your head could use a light resurfacing.

Oversized, wear, taper, or barrel shape tolerance on the cylinders is only .002 inch. If you can hone and not exceed that, then stock pistons and rings will do. If you exceed that tolerance, then you need to overbore by .010, .020, or .030--whatever will clean up the bore.

I am reasonably certain that with the clogged carb, the knocking you heard was due to combustion, not bearings. To split the crankcase, you must remove the 1/4 X 20 3/8 head flange bolts and the bearing bolts. The top will have one 9/16 head bolt and one nut. there will be two allen head cap screws inside the reed opening so you must remove the carbs, manifold, and reeds to access them. The reat will be standard 9/16 head, 3/8 diameter bolts. At the very bottom of the block will betwo slotted fillister head 1/4 X 28 screws, They must also be removed and usually you need an impact screwdriver to loosen them. Connecting rods are matched so mark them. Cap bolts are 12 point 1/4 X 28. Wrist pins will need to be pressed out of the pistons.

And while you are at it, it may have been mentioned before, drop the lower unit and replace the water pump impeller. Most marine stores and iboats will not have the correct impeller so buy one from franzmarine@aol.com.

When dropping the lower unit, there will be a bolt--on your engine most likely a 12 point 5/16 head X 6 inches long--inside the exhaust snout. This must also be removed.

 

[spool]

Re: '73 chrysler 105 surges at WOT then looses power

Re: '73 chrysler 105 surges at WOT then looses power

Thanks Frank,

I did mis read the manual, as i only loosened the bolts i did not take note of the torque setting, but i know what 20ft/lb feels like on my torque wrench.
I'm pricing up parts but its going to need atleast 3 new pistons ( i'll do 4 ), Hopefully the bearings are in good shape (cheaper rebuild)

how many bottom end bearings are there and what kind are used?

From what i can tell its caged roller bearings which should be less picky with loss of fuel/oil. I'll go back to my machine shop and see what they say. It's not the first engine i've rebuilt and im sure it wont be the last.. it is the first marine engine however.

hopefully a hone will clear up the scoring. If not, i'll order oversized pistons

I will be replacing the impeller and housing, I noticed a temprature gauge in the powerhead, i'll be connecting that up to a gauge in the boat aswell
I've heard there is a water seal problem with these engines, Is there anything else i should/need to do while the block is out?

 

[Frank Acampora]

Re: '73 chrysler 105 surges at WOT then looses power

Re: '73 chrysler 105 surges at WOT then looses power

Top ball bearing is a standard bearing. last time I bought one they told me it is used in Ford rear ends. If you want to replace it, you will need the bigpress in the machine shop. It is a tight press fit. The three center bearings are caged roller with split outer races. I never had a need to buy any so can't tell you if they are standard too. The rollers ride on the crankshaft. The bottom bearing is probably also standard, but is is a complete roller and seal assembly.

As I said before, wrist pins are a press fit. If using stock pistons, you need to make a "U" shaped .310 spacer to prevent the needles from being squeezed between the collars and prevented from rolling. Actually, the wrist pins can vary from a light interference fit to a light free fit in the piston. The press fit is through the spacer collars. You should also make a pillow block to avoid warping the piston while pressing in the wrist pin. I have the Chrysler tools, but I prefer to buy Wiseco pistons. they come complete with wrist pins, retaining circlips, and rings. You will need to buy the bearing kit. it consists of 26 needles and two spacer collars. If you own the machine shop, you should be able to get mechanics discount on the Wiseco pistons.

 

[spool]

Re: '73 chrysler 105 surges at WOT then looses power

Re: '73 chrysler 105 surges at WOT then looses power

Hi Frank, Unfortunately i don't own a machine shop or i'd probably have it rebuilt already !

I will be using 4x new Wiseco pistons, So correct me if i am wrong but the wiseco piston pins are not a interferance fit like the STD chrysler pins, they use a circlip insead?


Do the roller bearings have a collar that slips into the main caps & rods that contacts the rollers? or do they roll directly on the con rod and block/main caps?


I've already priced up the Piston kits and the Bearing kits and machine costs. I will be removing the engine and stripping it down over the next week and dropping it to the machine shop the following week. Once i know the exact damage to the bores i will order the pistons and bearings. (so i know the size)


I'd say the scoring was already there, i just damaged cylinder number 2 worse by running it dry.

 

[spool]

Re: '73 chrysler 105 surges at WOT then looses power

Re: '73 chrysler 105 surges at WOT then looses power

I stripped the motor down last night, haven't cracked open the crankcase yet but I inspected the
Bores further 1 is more or less ok and will be fine with a rehone

2 has a compression busting score and must be oversized

3&4 have not so bad scoring (comp test confirm that they were will sealing with only 10psi loss. I'm hoping to get away with just a hone on these.

Correct me if I'm wrong but if I only oversize cylinder 2 won't it unbalance my engine or do say weisco remove excess material to keep the weight the same?
Should I just re-bore all 4? I will be replacing all pistons.

Frank/Jerry, from what I can tell the 105 and 115hp/130hp have the same bore and stroke, I imagine the lower units are a little different but is it just the power head that differs? From what I can tell it's just the compression that makes up the power difference between the models. So if I shave the powerhead I should beable to screw a few more ponies out of it? From what I can tell the 105 runs about 7.5:1 - 8.0:1 compression which is pretty low. Here in aust we have 98 octane pump fuel which I imagine I'd need to use with higher compression to avoid detonation.. Just a thought.

 

[Frank Acampora]

Re: '73 chrysler 105 surges at WOT then looses power

Re: '73 chrysler 105 surges at WOT then looses power

Rod bearings are 16 loose rollers with two half cages to keep them spaced. They ride directly on the crankpins and the big ends of the rods. Rods are cracked cap so each is a matched rod and cap AND the cap can only go on one way. Mark them. The rods also go a specific direction on the piston. Mark the up side. Crank bearings have a split outer race held by the crankcase and a spring clip. These is a hole in one race and a pin in the block to keep them from rotating. Rollers are captive in two hlaf circle plastic cages. They ride directly on the crank. Crank bearing surfaces are fully hardened.

The engine will not notice the overbore on one cylinder. The displacement is so small that even an .030 overbore on one cylinder only gives a fraction of a cubic inch more--do the math: 2,80 stroke X 3.3125 bore. 99 cubic inches stock.

Oversized pistons are balanced to factory weight and don't cause an imbalance. Wrist pins are loose fit in Wiseco pistons and retained by circlips. Bore only those that need it unless it offends you aesthetically and you want to have all four done. If you do all four, you will essentially have a new engine, but you will still have an old lower unit and you will invest more money than the engine will resell for. Buyers don't care that the engine is rebuilt, only that it is old and a Chrysler

While the three engines you mentioned have the same bore and stroke, they are ported differently. ( I thought the 115 was 2.80 X 3.375 but the memory sometimes fails) That in addition to higher compressio and different carbs is primarily what gives the higher horsepower.

Factory recommends only facing the head by .010, but there is enough clearance that you could mill off about .060

If you can find an old junker Chrysler or Force 120 or 125 with TC carbs, you can swap in the manifolds and TC carbs which have much bigger venturis. 1 5/8 vs 1 5/16 for your WB carbs. While the top end won't improve too much, it will make your 105 honest instead of the 90 it delivers now and the hole shot will be better.

Lower units are all the same at 1.76 to 1 ratio. If you can find a matching year 90 HP, that has a 2 to 1 lower unit and will improve both hole shot and top speed by as much as 3-5 MPH

While you have it apart, you can square the bypass ports for a little increase in power. DO NOT do the exhaust ports. Because the engine has a common exhaust chamber and because #2 and #3 fire next to each other, AND because the ports are open for about 120 degrees, giving a 30 degree open overlap, porting the exhaust without other special modifications will actually reduce power below stock. I have been told, but have never tried it myself, that the port tops can be raise about .060 for increased power (this changes the port timing and may be the difference in the 130.)

BTW: If you happen to find a junker 125, with a good crank it has a 2.875 stroke and it will swap right into your block. However, port tops must be raised to accomodate the extra stroke. You would need to measure both blocks. -- just a couple of hints in case you are hot rod and tech minded.

 

[spool]

Re: '73 chrysler 105 surges at WOT then looses power

Re: '73 chrysler 105 surges at WOT then looses power

Thank Frank I thought that Wiseco would keep the weight the same as STD pistons for this exact reason, I can live with a larger bore on 1 cylinder, I've compared 20thou pistons to STD and can't really notice the difference. I was just worried about unbalancing the spinning mass.

I'm not too eager to take my carbide cutters to the block for the sake of a few extra ponies, I'd want a flow bench to test/make adjustments and it just isn't worth the time/money.

I need to mill the powerhead anyway so i may take a little extra off to bump up the CR which should help give it a little more bang, i figured the carbs would be different given at WOT the max rpm is round 5000rpm. and the higher the HP the higher the max RPM.

At this stage i plan to Bore cylinder 2 and hone 1,3,4 and fit all new forged wiseco pistons. I'd rather not take off material where i don't have to.

The last engine i built was a 450rwhp inline 6..

Are the bottom end bearings typically reusable? I'm being cautious about spending alot of money on a 40 year old engine, not because i'm tight/short of money. I plan to keep it for a few years anyway.

I started undoing the flywheel nut until i noticed the thread was coming out with it, is this just a stud that bolts into the crankshaft? I guess i'll know more tonight when i pop the crank case.

I will be marking everything before i disassemble. i know the importance of putting it back together correctly.

 

[Frank Acampora]

Re: '73 chrysler 105 surges at WOT then looses power

Re: '73 chrysler 105 surges at WOT then looses power

ALL bearings are reusable--with the exception of small end bearings if you buy Wiseco, They may probably show a light discoloration, light brown to light blue. Unless they are spalled or corroded the color will not hurt--it is "work hardening." However, if the bearings are a deep blue from heating and overload, or if they show pitting, corrosion or spalling (flaking)then they are not reuasable. This type damage is progressive and no amount is acceptable. Any amount will SIGNIFICANTLY shorten service life. Same thing goes for rod and crank bearing surfaces.

Now, your comment on the flywheel nut makes me suspicious. The threads are part of the nose of the crankshaft and the nut is USUALLY a nylock insert. It is usually 3/4 inch fine thread so if it is smaller and indeed a stud, then someone has drilled and tapped the crank--not an easy task. So, no matter what, you need to remove it. If the shaft has the threads broken, then you have no choice--you need to replace it. Uncommon to see this type of damage though. Usually the crank will break at the first journal.

 

[spool]

Re: '73 chrysler 105 surges at WOT then looses power

Re: '73 chrysler 105 surges at WOT then looses power

Interesting, It was turning out as if it had thread until it gave up some resistance at which point i decided not to force it.
The nut has a nylon lock on it. Its possible i could have a broken crank? I guess ill find out when i tear the block down tonight.

EDIT, I was wrong the nylon had just locked to the crank and was tight, removed the nut!
I can't remove the two flathead screws at the trans end, they're rusted!
/ sized in. I'll need to use a easyout and replace them with bolts.

I'll take some good photo's of the bearings when it crack it open with a good camera and not my phone. Not sure what i'll find yet.


Is there any trick to splitting the block from the trans? ive got all the bolts undone but short of forcing it apart it does not want to budge. The lower leg is still in place.

 

[Frank Acampora]

Re: '73 chrysler 105 surges at WOT then looses power

Re: '73 chrysler 105 surges at WOT then looses power

I suspect that by trans you mean the midleg. No trick, some are just difficult. The studs tend to corrode into the mounting flange. After you remove the six bolts in the front and the six stud nuts in the back, you need to pry up on the two pry points at the back of the match plate. You need to remove the lower cowl to do this.
You may also need some heat and penetrating oil on the studs to free them. Some are really stubborn.
Two flathead screws at the trans end? Puzzled. Photo please.

 

[spool]

Re: '73 chrysler 105 surges at WOT then looses power

Re: '73 chrysler 105 surges at WOT then looses power

Ok here are the photo's.

Sorry I'm not familar with all the marine engine specific parts yet, I do mean midleg, what exactly is the lower Crowl?

I get the feeling this motor has never been dis-assembeled as everything seems to be rusted in place

 

[Frank Acampora]

Re: '73 chrysler 105 surges at WOT then looses power

Re: '73 chrysler 105 surges at WOT then looses power

OK! Those are called fillister head screws and you will need an impact screwdriver to loosen them. Impact screwdriver is a hand held tool with changable screwdriver tips. You set the tip in the screw slot, twist the tool and smack the top with a hammer. Simple and effective. The screws are in there tight from the factory and since no water or other touches them they rarely rust or corrode.

The lower cowl or pan is the cast aluminum part that the cover sits on. The contol cables fuel line and electrical cable pass through the front.

In the photos, you can see the bottom locating pin. It is a light press fit in the case and the top one is diagonally opposite. You must drive these pins out with a punch before trying to separate the crankcase halves. The reason they are there is because the crankcase is line bored. SO: During manufacture, first the holes are drilled, then the pins are inserted to keep the halves in alignment, then the case is bored. This means that due to manufacturing tolerances, crankcases are specific. Fronts and rears can not be swapped because each is slightly different from others.

Although the bearings will correctly locate the two halves, when reassembling the crankcase, you will also first re-insert these pins before bolting it together.