1974 105hp chrysler Lower End Questions!

[hbryant123]

On my lower end i am having some issues, first off every time i change gear lube there is water mixed in so its milky! Second of all its developed a leak where the lower end meets the rest of the leg! I am wondering If i can sorta rebuid my lower end with new seals, gaskets, and bearings? If so how do i go about getting the parts and information about doing so? I would also like to say as of now my lower end functions normally in forward and reverse! Thanks IN advance!

 

[henleyhale]

Im not much of a lower unit guy, but i think your oil seal has gone out in your drive, and the water carrier seal atop the water pump has gone out as well. My seloc online subscription has procedures for both of those processes as well as parts and part numbers for what you need. Its where id start on this venture for certain. Good luck

 

[jerryjerry05]

This site sells parts. Not sure they sell the seal kit but b o a t s . n e t does.
First pressure test the unit before you replace any seals.

My motors, both, weep at the drain plug and allow water in.
No fix for my problem.

What seals do you have?
The plastic one? They should be new every time you change the oil.
I use Mercury's drain plug seals.
henly: the seal "atop" the pump is there to keep water in. Not oil??

Pressure test first.

 

[Frank Acampora]

That lower unit used standard seals and bearings. You CAN buy them at a local bearing supplier but you must specify all stainless. My bearing supplier says the seals are all stainless but I find that they rust so someone is either lying or doesn't know his product. At any rate I now buy seals from a marine supplier.

There are several places where your lower unit can leak: 1. bad gaskets at the fill and drain plugs. 2. worn shift rod seal. 3. Prop shaft seal. 4. drive shaft seal (under the water pump). 5. The rubber O-ring seal around the gear-case to mid-unit joint.

If the shift rod seal is leaking, very often it can be re-sealed simply by taking an appropriately sized socket and a piece of pipe. Put the over the seal and tap it further into its seat. There should be a slight drag on the shift rod but not excessive so do it a little at a time.

Like jerry said, pressure test the lower unit so you know exactly which seal is leaking. Since it is a 1974, many sites will not carry parts for it. certainly, iboats will not. You can try marineengines(dot)com or boats(dot)net. If they don't have what you need try Franz at franzmarine@aol.com. Note that the dot in parentheses is actually a period. The forum will not let competing sites be posted

When you go to drop the lower unit, there is a "hidden" screw inside the exhaust snout. you need to remove the snout to access it. Depending upon which lower you have ( If the rear of the mid-leg drops almost straight down to the lower unit) the screw may be a 5/16 12 point head and may be six inches long.

 

[hbryant123]

Thanks for the replies, i have never really worked on my lower unit before. In my area there is a local bearing supplier that has always been able to get me any bearing i needed or seal. So how do i pressure test the lower unit? I have put back extra money to put into parts and tools for this job! Thanks again
-henry

 

[Frank Acampora]

Well, I am sure that someone makes a pressure tester but personally I would make my own out of a simple fitting to go into the vent screw hole, some tubing, a shut-off valve, and a bicycle pump. You only need to put about 10 PSI into the lower unit and dunk it under water. Air bubbles will pinpoint the leaking seal.

 

[hbryant123]

Ok that sounds easy enough! So when you say vent screw hole do you meen the hole that has to come out when draining and filling the lower end?

 

[Frank Acampora]

Your engine has a lower drain screw and an upper vent screw. Drain the lower unit so you don't blow oil into the water. Replace the drain plug and screw your pressure tester into the vent plug. submerge the whole lower unit and look for air bubbles.

 

[henleyhale]

This site sells parts. Not sure they sell the seal kit but b o a t s . n e t does.
First pressure test the unit before you replace any seals.

My motors, both, weep at the drain plug and allow water in.
No fix for my problem.

What seals do you have?
The plastic one? They should be new every time you change the oil.
I use Mercury's drain plug seals.
henly: the seal "atop" the pump is there to keep water in. Not oil??

Pressure test first.

pretty sure i was talkin bout the seal atop the water pump to keep water in the tube going up to the motor. Heck its past the gear lube, unless he is running that motor round bp's wells.

 

[henleyhale]

Pressure testers are easy to make, i use brass fittings to hook up to an air hose piece then put a t in the other end pit a gauge on top a ball valve and a male quick connect fitting after that, hook it up to a compressor turn the ball valve till you achieve your pressure then close it and let her sit. That same tester can do a leak down in a cylinder, locate a leak in a pool pipe, or in your house, its a handy thing all men should own

 

[Frank Acampora]

Jerry and Henly: The seal on top of the water pump is actually redundant. The impeller rides on the stainless plate and the internal top of the water pump casting, sealing the water inside the pump. The engine will run quite happily and pump adequate water without the seal, assuming the pump casting and impeller are not worn. In fact, the later Force/ Mercury pump does not use a top seal at all. There is a garden hose type washer on top BUT there are two weep slots under it. So that washer does nothing as far as sealing the pump

As an aside: Only adequate is a very apt description of that design water pump. Later pumps used a higher impeller that was about 30% larger and when Force went to the Mercury pump the impeller was twice as high--all cooling the same basic block.

If the drive shaft seal under the water pump fails completely, water will blow down into the lower unit, displacing the oil, and within a short time destroy the gears. If it is only slightly worn then the oil will appear milky. Pressure test the lower unit with the water pump removed so you can clearly see the condition of the seal.

 

[henleyhale]

Jerry and Henly: The seal on top of the water pump is actually redundant. The impeller rides on the stainless plate and the internal top of the water pump casting, sealing the water inside the pump. The engine will run quite happily and pump adequate water without the seal, assuming the pump casting and impeller are not worn. In fact, the later Force/ Mercury pump does not use a top seal at all. There is a garden hose type washer on top BUT there are two weep slots under it. So that washer does nothing as far as sealing the pump

As an aside: Only adequate is a very apt description of that design water pump. Later pumps used a higher impeller that was about 30% larger and when Force went to the Mercury pump the impeller was twice as high--all cooling the same basic block.

If the drive shaft seal under the water pump fails completely, water will blow down into the lower unit, displacing the oil, and within a short time destroy the gears. If it is only slightly worn then the oil will appear milky. Pressure test the lower unit with the water pump removed so you can clearly see the condition of the seal.

Good description thanks

 

[hbryant123]

Very interesting! I have a spare parts lower end, i may take it apart and see what is inside and use it for part numbers to locate bearings and seals! I feel like having good seals and bearings will help other parts to last!

 

[Frank Acampora]

If you just want to take it apart, that's OK. If you want to re-use it and you remove the drive shaft understand this: The pinion nut should not be re-used. The pinion nut MUST be torqued to a specific value--I forget, look it up-- The two tapered roller bearings that locate the drive shaft are pre-loaded by the pinion nut so it needs to be the correct tightness.

If you stake the pinion nut on three flats ( you will see the factory marks) with a punch, you can then re-use the old one. This slightly deforms the nut and threads and makes it self-locking.

 

[hbryant123]

Thanks for the advice! I decided to just remove my lower end the check everything out and hopefully replace all the seals. I know maybe 10 years ago my dad had taken the lower end off and replace the Impeller and then 5 years before i think he had to replace something like a gear but he couldn't recall. Once I remove the lower end tomorrow i will post what i find and some pictures if i can!

 

[Frank Acampora]

I haven't done one of those lower units in probably 12-15 years. Not to discourage you but they are poorly designed and there is no real selection of props available. The thrust pin drive is a horrible engineering design--imagine: All the forward thrust is taken by a single 5/16 pin and the bronze prop hub. A tiny water pump impeller. Yeah, it works but---

Don't misunderstand me: The later three bolt models looked really pretty. These lower units work and can deliver a decent amount of speed but the power was rated at the crankshaft. Your 105 actually delivers somewhere around 90 HP.

. The newer one piece lower unit is a much better design and also is faster. I proved this by taking a 90 HP block from a two piece lower and mounting it on the newer one piece mid-leg and lower unit. The same boat and block ran 3 MPH faster.

I still have a couple of lower units and a bare mid-leg Hanging around the garage but I don't bother to mess with them. I am preparing an 85 with that lower unit for sale and because it is so old and does not have power TNT, it will sell for about 350 bucks.

 

[hbryant123]

You are right about that! I have one spare prop and few that are more torquey from a pontoon engine and thats it. On my boat it originally had a 1991 85hp force i used the power tilt trim from the 85 on my 105. It seems like with me and one passenger the boat takes off fine and gets up to speed well with a top speed of about 38 mph. With two other passengers, adding about 300-400 extra pounds it struggles to plain out. Could the engine being to low in the water be the cause or am i not using the trim properly? When i bought my boat i was 17 and never had had been around boats with power tilt so i am new to that! DO thoses "whale tales" help any?

 

[hbryant123]

I removed the Lower end this evening to do some investigating, i found the shift rod seal to be pretty much GONE, the seal under the water pump looked OK, the impeller was showing some signs of wear, a few fins were cracked. I think I am going to find the numbers on the seals and see if my bearing supplier can get me seals. How do i go about removing the seals?

 

[Frank Acampora]

That seal was used on almost every Chrysler and Force engine above 20 HP.--that is up until mercury started putting the bellows seal on the dual exhaust lower units and until Mercury put their lower units on the engines.

SO: look for any engine before 1989 and the seal number will be the same.

The seal costs about 8 bucks. It is installed metal side up. Use a socket with a piece of pipe to drive it home. You drive it to compress it and there should be a slight drag on the shift rod. It should not be loose and should not be tight enough to bind.

There can be a few reasons why the boat will not plane with an extra 400 pounds. You did not say the size but smaller boats are way more sensitive to load than larger ones. Hydro=foils: Some people swear by them, some swear at them. One might help but you never know until you install it. New, cheap ones cost about 35 bucks and sometimes you can find used ones on ebay and craigslist. Either way it is not an expensive gamble and you just might be happy with one.

 

[hbryant123]

My boat is about 16 foot long. I have found a lower end seal kit from sierra for about 35 bucks http://www.ebay.com/itm/Lower-Unit-...061-/380865095046?hash=item58ad542586&vxp=mtr , this seal kit looks like it has what i need, please take a look and let me know what yea think. As for the seal under the water pump how should i remove that one? Also that gear on the end of the drive shaft seemed loose on the shaft but the nut is tight? The bearings did not look abnormal to me, if i replace them how do i remove the races?

Thanks frank for all your advice!