4.3L vs 5.7L Outdrive Gearing (16T/19T)

[funk6294]

Re: 4.3L vs 5.7L Outdrive Gearing (16T/19T)

Ok I just reread this thread and you mentioned that for the test run you borrowed a 3 blade 17p prop and when running you were hitting 42-43 at 3800 to 4k rpm but never were able to get a wot run in due to the outdrives untimely demise. After swapping drives to the v6 drive you borrowed a 4 blade 19 pitch and are hitting 4600 rpm and 42-43 mph. Based on that we are 1) not sure that the 17p prop was right to begin with, though we do know you had more throttle to go, 2) the change in props not only increased pitch but number of blades, so we really don't have a good apples to apples comparison.
So I am hoping before you get to discouraged you get with a local prop shop that will let you ry some different props to give this a shot before you put the money into a gear swap.

 

[triscadek209]

Re: 4.3L vs 5.7L Outdrive Gearing (16T/19T)

The 19p 4blade is my prop that came in the day after the test run ironically. The 4600 RPM was at WOT. The 3800-4k was just cruising, with plenty left to go, we did briefly go WOT throttle the first day but due to roughness cutting across the lake to get to the south side which had wind broken smooth water, I had shut it back down to 3800-4000. The water was rough enough that I wasnt able to get a good reading and calculations on my guages, once we hit the smooth water and was about to open 'er up... BOOM.
If I go with 23p 3blade, in theory I should gain several mph and lower my WOT to around 4200?

 

[triscadek209]

Re: 4.3L vs 5.7L Outdrive Gearing (16T/19T)

How hard is a gear swap and which gears are the ones needing swapped? upper? Lower? Most likely Id just do it myself. I have a few buddys with access to 20+ton presses if need be

 

[funk6294]

Re: 4.3L vs 5.7L Outdrive Gearing (16T/19T)

Not sure how hard they are to swap as I have never had a set out. A quick check on google is showing the lowers are the same and that the difference lies in the upper.

 

[triscadek209]

Re: 4.3L vs 5.7L Outdrive Gearing (16T/19T)

Correct.

 

[triscadek209]

Re: 4.3L vs 5.7L Outdrive Gearing (16T/19T)

Well, good news... kinda. Pulled my old stern apart (separated upper and lower) and tore in to the upper after talking to the guy at the local prop shop. Strangely enough, its pretty simple pullin the gears out, however the vertical gear is the one that had the bearing seize. Definitely going to need a press to get it out being that the bearing exploded. Have a friend going to pop it out for me then maybe next week swap the gears in my other upper and get my beloved performance back. Just start taking some of the bolts out and its pretty self explainitory, not much to it really. I dont see how boat mechanics get off charging so much honestly. These things are like legos lol.
First, Im going to try a new Solas 23p 3blade that should be in tomorrow, I was able to talk the local shop into trading me for a couple old busted up props. If I dont feel satisfied that it brought the boats potential back, gear swap it is.

 

[MikDee]

Re: 4.3L vs 5.7L Outdrive Gearing (16T/19T)

Be careful with the gear swap, the gears need the right preload on them to work right! I found this out the hard way, after replacing the upper gears in my drive, noisy, and wiped them out in no time!

 

[triscadek209]

Re: 4.3L vs 5.7L Outdrive Gearing (16T/19T)

Can you go into a bit more detail?

 

[Howard Sterndrive]

Re: 4.3L vs 5.7L Outdrive Gearing (16T/19T)

Have a read of the service manual and then you'll know why those darn mechanics charge so much.

 

[triscadek209]

Re: 4.3L vs 5.7L Outdrive Gearing (16T/19T)

But I'm putting the same gears in that originally came with the boat, only difference is it's in a different casing...

 

[Lou C]

Re: 4.3L vs 5.7L Outdrive Gearing (16T/19T)

Its like setting up a differential, something honestly I would not try myself unless I had a pro teaching me. I've done everything on the Cobra I can short of internal dis-assembly which luckily for me has not been needed. This is why I still buy parts locally, to keep my relationship with a very good OMC mechanic for the things I can't do myself.