3 different thrust washers! which one to use!??

[bigguy6f4]

hey guys, Im having a bit of trouble trying to get my new prop install finished.

Pictures at the bottom.

Before i state the problem ill give a lil background info about my boat as it will make more since later.

i have a 1971 tri hull mercruiser 165 with 250ci gm motor.
I got the boat running in great condition for only 500 bucks cuz they didnt know why the prop would only work at idle. (spun the bushing on the prop! hehe)

Anyways i bought the boat and it came with another lower gearcase they said the previous owner gave to them. and by looking at my currently installed gearcase i could see newish rtv silicone around the gasket area so i knew it was not origional equiptment. and im going to ASSUME that the spare gearcase was probably the factory equipment.

So anyways i went ahead and got a newer style prop and the salesman gave me the newer thrust washer saying i will need it to have the correct spacing.

So anyways i pull the old prob off, pull the thrust washer, and installed the new one and i could tell right away something wasnt right. it was loose fitting and slid all the way on the shaft till it hit the aluminum casing. Upon closer examination i found the new thrust washer has a beveled inside. and the olderone i just pulled off does not.

And when i compared the shaft of the installed lower unit to the spare i had i found the spare unit had a beveled area that would allow the thrust washer to slide and sit tight. And on top of all this the spare unit had another different thrust washer alot like the new washer the sales person gave me but just about twice as thick.


So just to set things straight.

the washer on the LEFT is the NEW washer. it is the thinnest and has a beveled inside that will NOT work on my current lower gearcase.

The MIDDLE washer is the assumed factory thrust washer that is thicker than the new waser and still has a beveled edge. Will NOT work on current gearcase.

the Washer on the Right is the currently installed Lower gearcase. It has NO BEVEL cut into the inside and NEITHER DOES the installed gearcase on the output shaft. Its absolutly huge.

All 3 washers have the correct cut to fit the prop.

when i compared the 2 gearcases its easily seen that the inside of the currently installed gearbox is inset about 1 inch more thus requiring a bigger washer to space it out properly.


So here are the questions im wondering about. lol

1. What the heck is my currently installed lower gearbox???
2. If i used my lathe and trimmed down my big thrust washer so that the prop is sitting correctly would that be ok? My eyeball says it needs to be about 1/4 inch shorter to have the correct stance.

Also on a side note. Its obvious the 2 smaller washer are set inplace according the bevel. However ill state the none beveled output shaft as a protruding area the bigger thrust washers nose hits thus keeping it from contacting the housing itself.


The only reason for changing props is for ease of finding different pitches and other props in case of emergency when im on vacation.

Any sugestions?

 

[Bondo]

Re: 3 different thrust washers! which one to use!??

1. What the heck is my currently installed lower gearbox???

Ayuh,.....

Whatever it is,...
It's Older than Dirt,+ That's the Problem you're going to have, trying to fit a Prop on it......
It's Obsolete.....

 

[ziggy]

Re: 3 different thrust washers! which one to use!??

Whatever it is,...
It's Older than Dirt

in lookin at service manual #1. the thrust hub on the right, the big one is right for a prop shaft that don't have the bevel. like bondo say, must be older than dirt... or at least a low serial number 1 drive.... i've had nothing but older than dirt 1 drives. but i've not seen or delt with what you've got....

when i switched props on my 1 drive i had yer middle pic thrust hub. the new style prop required me to use the thin one. and even that wasn't thin engouh. i still had to notch the trim tab..... but these aint yer problems, yers seems to be the no bevel on the prop shaft..... i don't know what yer answer is to putting a different prop on it... sorry..... have ya tried the merc dealer.... maybe they got different thickness old style (the right pic) thrust hubs?

 

[JustJason]

Re: 3 different thrust washers! which one to use!??

What kind of prop are you using?? is it a quicksilver? a michigan wheel? etc??? where did you buy it?

 

[bigguy6f4]

Re: 3 different thrust washers! which one to use!??

Thanks so much for the responses!

The new prop i have now is a solas.

I have 2 other props that are older style props that would be original style.
one is chewed up and cost 70 bucks to fix, the other is chewed and needs a new bushing installed and that is 70 plus 50 to fix.
the new was 120 bucks brand new and the pitch i was wanting.

Can someone please measure how close the prop needs to be in relation to the lower unit. im gonna try to adapt what i got.

The way the big one is designed it would be easy to cut on a lathe and make work.
As it is now with the big spacer, it almost clears the trim tab.

 

[Don S]

Re: 3 different thrust washers! which one to use!??

Moving to Prop Forum.

 

[ziggy]

Re: 3 different thrust washers! which one to use!??

As it is now with the big spacer, it almost clears the trim tab.

if it's just missing. i'd go the other way.... grind the trim tab.....

 

[bigguy6f4]

Re: 3 different thrust washers! which one to use!??

can anyone say for sure what the tolerances are for the prop being in relation to the gearcase itself. I have no idea if its even critical or not. however since the exhaust exits thru the prop i thought it best to get as close as possible to factory tolerance as possible. i have no idea if the exhaust exits around the prop instead of thru the prop will have any effect on performance.


On a side note. you know the splined bronze bushing you install after the prop and before the lock nut. actually is part of the locknut i guess. The splined bronce peice only gets about 3/16 of bite on the shaft's splines. so im guess i need to cut the thrust washer so it gets about 80 to 90% of the lock nuts splines grapping onto the outshaft.

That make any sence?

Thanks everyone for the fast responses! Im hoping to get the thrust washer cut tomorrow. And just want to give myself just a tad more confidance im going about this the best way possible for using my current setup.

THANKS!!!!

 

[Don S]

Re: 3 different thrust washers! which one to use!??

You shouldn't have to cut anything. All props are always installed on boats without all that problem.
Get the proper thrust washer for your prop and drive and be done with it.
The picture ziggy posted shows how the prop should set next to the lower unit.

 

[bigguy6f4]

Re: 3 different thrust washers! which one to use!??

Not to be rude Don, I really appreciate your wanting to help. But.....

I dont think youve read my entire post. if so youd find i currently have such an old lower gearcase that nobody even knows for sure exactly what it is or how old. and since it does not have a beveled output shaft and requires a huge thrust washer with no inner bevel. Im gonna say an adaptor from that old of a unit to a new prop has probably never been made. At least not without changing to a newer lower gearcase

So therefor advice to install the correct thrustwasher and be done is not really feesable.

And as with anything mechanical Or anything being fabbed up from bits and pieces. Correct measurements and or factory specs are important vs "look at that pic thats the way it should look."

There is no real way to know how far into the case that prop is installed. Not without someone actually measuring or looking in a manual.

I really dont feel like paddling a 2500lb boat from the middle of the lake due to a mechanical failure cuz i didnt do the job properly.


However thanks for the try.

Perhaps someone can come up with the small important details i need.
Mainly.....

1. Where exactly (as in measurments) does the prop need to set.

2. Will any adverse affects (other than having to trim the trim tab) come from having a Prop installed out too far from the gearcase.

3. On a side note. you know the splined bronze bushing you install after the prop and before the lock nut. actually is part of the locknut i guess. The splined bronce peice only gets about 3/16 of bite on the shaft's splines. so i guess i need to cut the thrust washer so it gets about 80 to 90% of the lock nuts splines grapping onto the outshaft.

Here is a picture of the part that only grabs 3/16 of the splice.

 

[ziggy]

Re: 3 different thrust washers! which one to use!??

before ya cut up your thrust hub. ya should have a look at this..... "http://www.marinepowerservice.com/BoatingStore/lookup_parts_merc3.cfm/select/yes/block_nbr/7/index_nbr/1562/MIX_SEQUENCE_NBR/3630/search_text/1DR/Doc_Part_nbr/%2038973/app_style/1%20Drives/serial/1776349%20THRU%202065189.cfm"

that thrust hub is nla..... are ya sure ya want to cut it up?

 

[ziggy]

Re: 3 different thrust washers! which one to use!??

one more thought too. i assume that solas is ss. personally, i'm a little leary of putting a ss prop on my old drive. the drive shaft in the lower has an oring groove by the splines.... this oring groove has been known as a weak point for the drive shaft to break at. apperently the oem caught on and in the later drives eliminated that oring groove. i have the groove on my drive so i'm sticking with an alum. prop. if i strike something, better to have it ruin my prop than my drive shaft. at least i feel i have a better chance anyways for the prop and not the drive shaft. best i can do with what i got anyways....
another thought too. don't know what pitch that solas is... but my 165 had trouble reaching wot spec. with a 21P alum. fan blade style prop. i run a 19P alum. and for my application, it's perfect. 4300 on the nose. 44 if i trim to excess, which i don't do. just food for thought for ya man.....

 

[Bondo]

Re: 3 different thrust washers! which one to use!??

2. Will any adverse affects (other than having to trim the trim tab) come from having a Prop installed out too far from the gearcase.

Ayuh,.....
If there's Any gap,... It'll Ventilate the prop....

3. On a side note. you know the splined bronze bushing you install after the prop and before the lock nut. actually is part of the locknut i guess. The splined bronce peice only gets about 3/16 of bite on the shaft's splines. so i guess i need to cut the thrust washer so it gets about 80 to 90% of the lock nuts splines grapping onto the outshaft.

That Only locks the Nut,+ it Must be able to compress against the Thrust Hub,.....
So,... 3/16" is about Right.....

 

[bigguy6f4]

Re: 3 different thrust washers! which one to use!??

Thanks ziggy and bond-o! those last 3 posts were very helpful!

And as far as cutting it up, im going to go ahead and check for clearances to make sure there is no gap for it to ventilate. then trip the thrust washer to fit.
Then what ill do is make another bushing that i can slip on the output shaft, then install my new shorter thrust washer to bring me back out to stock thrust washer depth. that way i can use my old props when i want to use my 19 pitch
aluminum prop. or if i want to switch to my new ALUMINUM solas 17 pitch then ill just remove the little spacer bushing so that the thrust washer slides a little further so the new prop fits right. That make sence?

And thanks so much for that diagram of my old unit! ive searched high and low and had no luck finding such a thing!

Again all my props are aluminum. And after your advice ill stick with aluminum.

I wonder how much it would cost to rebuild my other lower unit that has the beveled shaft? everything spins freely but its been sitting outside for years uncovered.

 

[bigguy6f4]

Re: 3 different thrust washers! which one to use!??

also I went with a 17 pitch prop due to this.


with my 19 pitch with 2 people in the boat i could hit about 4100rpm max
with 7 people in the boat im at about 3900rpms.

i custom made my own wake tower, and need some torque to keep the boat on sub plane.

so im hoping a 17 pitch will give me want i want. hope its not too much.

my boat is a 18 or 19 foot kenny rodgers tri-hull with 165 mercruiser. 250 6cyl gm engine.

From some comments ive seen im gonna guess 4400rpm is the sweet spot?

 

[Bondo]

Re: 3 different thrust washers! which one to use!??

I wonder how much it would cost to rebuild my other lower unit that has the beveled shaft? everything spins freely but its been sitting outside for years uncovered.

Ayuh,....

There was a change in the spline count on the vertical shafts along about that time,...
My Guess is,...
That lower case probably won't fit your upper case.....

From some comments ive seen im gonna guess 4400rpm is the sweet spot?

Ayuh,.... Sure Is....

 

[bigguy6f4]

Re: 3 different thrust washers! which one to use!??

well im gonna guess that the current gearcase isnt the stock one. because the paint doesnt even match. othe old one that came with it matches perfectly and its a beveled shaft. so im faily sure if i rebuild that one it will bolt right in.

 

[bigguy6f4]

Re: 3 different thrust washers! which one to use!??

and for anyone who looks at the post in the future,,,, took exactly 1/4 inch off the nose of the thrust washer with a lathe and the fit was beautiful! the nut and lock nut fit great catching about 90% of the spline. And i needed to trim about 1/4 inch off my trim tab total. Im very pleased!

Thanks for all who helped me!