1973 chrysler 70hp model 707hf outboard propshaft endplay

[christo555]

after replacing the rear propshaft bearing race carrier in my lower unit, i found that the propshaft went in and out about .062".
the tapered roller bearings at each end of the shaft which sit in the respective races determine the propshaft location in the case and therefore the engagement of the forward and reverse gears on the propshaft with the pinion gear,and the engagement with the rear propshaft oil seal.
in my glenn's manual, it says very important to have .000+/-.001" endplay on the propshaft while my seloc seems to say that .010+/-.001" is required.
web search on tapered roller bearings in general seems to say .000" with preloading of amount i can't understand as it talks about force necessary to rotate the shaft.
the end play is adjusted by the thickness of the shims between the bearing race and the bearing carrier, so you have to make a endplay measurement with a dial micrometer, remove the carrier from the case, remove the race from the carrier, place the proper thicknesses of shims in the carrier, and then bang the race back into the carrier against the shims.
is all this necessary? should i just ignore the .062" end play because the rear propshaft oil seal can handle the propshaft side to side movement and the tapered bearings can handle slop in engagement between them and the race???
thanks for any thoughts on this,
christo555

 

[Frank Acampora]

Re: 1973 chrysler 70hp model 707hf outboard propshaft endplay

I seem to remember Clymers stating that endplay should be about .004 to .006. Too tight and for sure the lower unit will heat up and bind, stalling the engine. Then since it is in the water, it will immediately cool and the engine will start again easily. This drove me crazy on a 105 until I found that the previous owner had not pressed in the outer race all the way. There was no bearing clearance but interference.

I believe if you leave it as-is it will be OK. Remember the rear is a tapered roller, not at 45 degree angle and .06 end play will not translate to .06 side play.

That lower unit is a poor design and really old school engineering before better casting and accurate machining was available. That's why Chrysler designed the one piece lower to replace it. .010 endplay is the number assigned to the one piece lower unit.

 

[christo555]

Re: 1973 chrysler 70hp model 707hf outboard propshaft endplay

frank,
thanks for the advice on my endplay question. i had a really hard time finding the shims to put under the rear race in the the carrier, but finally did. so now i at least have a choice as to how much endplay i will have.
i have to admit i don't understand/know how/if the propshaft end oil seal can handle the "wobble" in the propshaft with the .062" play.
well, i have to wait a few days for the shims to arrive anyway so i can dream/have nightmares till then.
frank, thanks again for all your help,
christo555

 

[christo555]

Re: 1973 chrysler 70hp model 707hf outboard propshaft endplay

frank,
thanks for the advice on my endplay question. i had a really hard time finding the shims to put under the rear race in the the carrier, but finally did. so now i at least have a choice as to how much endplay i will have.
i have to admit i don't understand/know how/if the propshaft end oil seal can handle the "wobble" in the propshaft with the .062" play.
well, i have to wait a few days for the shims to arrive anyway so i can dream/have nightmares till then.
frank, thanks again for all your help,
christo555

update on 1973 chrysler 70 hp engine problems
well, it's running great now.
the end play of the prop shaft was actually about .015" after replacing the rear bearing carrier. and after reading frank's letter i decided that i would let it go and not try to shim bearing to .000" +/-.001".
the lower unit has a leak probably in the upper driveshaft seal and that's probably how water got into the lower unit over the winter as i had drained the unit of everything and left it in vertical position uncovered. doing this caused the bearing cap to freeze break during the winter. MY BAD!
after running the motor a total of 1 1/2 hours, i found maybe an 1/2 ounce of water in the oil when i test drained it. i'm not going to try and seal the lower unit to correct this as i have read that on a 40 +year old engine it would probably still leak and that amount of leakage is not really a problem.
also, lake powell which is one of the two places i would want to use the boat will no longer allow regular 2 cycle engines on pwc on the lake after december 31, 2012. (2 cycle engines with injected oil on pwc that meet the new emission requirements will be allowed)
thanks for the help you all gave me, christo555