1969 Merc 1000 Prop Question

NJCinMN · Jul 13, 2009

Hello all,
I've got a 1969 Merc 1000 pushing a 1969 Glastron V-163 (16.5 foot). I've done the full tune up, lync and sync, etc., and motor is running as good as I think it can. The original tach didn't work so I recently got a used newer quicksilver working with the minor wiring adjustment.

Went out yesterday with a typical load and at WOT only turning 4200 RPMS, recommended WOT 4800-5300. Currently running a 17-pitch aluminum prop. I'd like to run at the top end of the range. Will going down to a 15 pitch get me to 5300 RPM? Thanks, Nick.

countvlad · Jul 13, 2009

Re: 1969 Merc 1000 Prop Question

NJCinMN said:
Hello all,
I've got a 1969 Merc 1000 pushing a 1969 Glastron V-163 (16.5 foot). I've done the full tune up, lync and sync, etc., and motor is running as good as I think it can. The original tach didn't work so I recently got a used newer quicksilver working with the minor wiring adjustment.

Went out yesterday with a typical load and at WOT only turning 4200 RPMS, recommended WOT 4800-5300. Currently running a 17-pitch aluminum prop. I'd like to run at the top end of the range. Will going down to a 15 pitch get me to 5300 RPM? Thanks, Nick.

if you are 100% positive that the tach works correctly and motor is in good shape....if you switch to a 15 that will put you somewhere around 4600 rpms .... go with a 13 and see what it does.. that should put you somewhere around 5000rpms.... for every dropped pitch you gain 200 rpms

frm what ive heard merc dealer has a program where as long as you buy pro from them you can exchange it....

NJCinMN · Jul 13, 2009

Re: 1969 Merc 1000 Prop Question

Thanks, countvlad.
You know I've checked about everything I can think of, being mechanically inclined but not being an outboard mechanic, for this motor performance wise. New fuel lines, fuel pumps, rebuilt carbs, new spark plugs, lync & sync. Still I just don't feel like it's really where it should be. Top speed was 32 mph @ 4200 rpm.

Boat when new 700 lbs, 300 lb motor?, 6 gal gas, 2 guys about 190 each, 2 girls about 125 each, cooler, and anchor. Not a huge load total about 1800-2000 lbs...maybe thats resonable performance??

countvlad · Jul 13, 2009

Re: 1969 Merc 1000 Prop Question

NJCinMN said:
Thanks, countvlad.
You know I've checked about everything I can think of, being mechanically inclined but not being an outboard mechanic, for this motor performance wise. New fuel lines, fuel pumps, rebuilt carbs, new spark plugs, lync & sync. Still I just don't feel like it's really where it should be. Top speed was 32 mph @ 4200 rpm.

Boat when new 700 lbs, 300 lb motor?, 6 gal gas, 2 guys about 190 each, 2 girls about 125 each, cooler, and anchor. Not a huge load total about 1800-2000 lbs...maybe thats resonable performance??

if we were outboard mechanics i dont think we wouldnt be here right now...

from what i can gather you need to drop your pitch quite a bit... either 13 or 14.... and go from there

the only way to find the right prop is though trial and error

junior1113 · Jul 13, 2009

Re: 1969 Merc 1000 Prop Question

i would work on setup. before ever just buying a prop. where is cavitation plate in relation to bottom of hull. if there is room to go up performance will follow as well as wot rpms. can u post a pic of this? what is the condition of this prop?

NJCinMN · Jul 14, 2009

Re: 1969 Merc 1000 Prop Question

Setup is from the factory as this is the original boat and motor combo. The anti-cavitation plate is about an inch above bottom of hull. I don't think it's the setup as when I turn sharp and use the highest trim pinhole it will cavitate. The prop is in great shape, no dents, dings or rough edges.

countvlad · Jul 14, 2009

Re: 1969 Merc 1000 Prop Question

NJCinMN said:
Setup is from the factory as this is the original boat and motor combo. The anti-cavitation plate is about an inch above bottom of hull. I don't think it's the setup as when I turn sharp and use the highest trim pinhole it will cavitate. The prop is in great shape, no dents, dings or rough edges.

i dont know if raising it all the way up to the last pin hole is the way to go.... have you tried diffrent trim positions?

i guess a prop might not be a bad idea, go with a 15.. to have a spare one is better than none....

NJCinMN · Jul 14, 2009

Re: 1969 Merc 1000 Prop Question

I haven't gone thru the range of the manual trim. I have tried the second hole from most trimmed up with no change. You think I could be too far up...still thinking I probably will try a 15 or 13 pitched prop but I'll go out and run thru all the trim positions for the heck of it first. I'll post results.

countvlad · Jul 14, 2009

Re: 1969 Merc 1000 Prop Question

NJCinMN said:
I haven't gone thru the range of the manual trim. I have tried the second hole from most trimmed up with no change. You think I could be too far up...still thinking I probably will try a 15 or 13 pitched prop but I'll go out and run thru all the trim positions for the heck of it first. I'll post results.

do you have GPS? on my boat the max rpms and speed i get it when the gauge is in the middle... once i go above that point the rpms stay the same but i drop 2-3miles/h

what i would do is try diffrent trim holes and see the diffrences....

hwsiii · Jul 14, 2009

Re: 1969 Merc 1000 Prop Question

NJ, IF you can find a 14" pitch for a motor that old it will be as close as you can get to the right one. It should increase your RPM to right at 5,100, with the same weight you are carrying now and be right at maximum RPM with one person. If you can't you need to get a 15" and your RPM will be at 4,700 to 4,800 loaded like you are now and about 5,000 RPM with one person.
A 13 pitch would raise the RPM to about 5,500 RPM with 4 people and potentially 5,700 RPM with one person, and with an older motor I don't think that would be good.
Right now with 4 people in the boat you are running right at a 20% slip and that is good with 4 people. Changing to a 15" pitch ought to bring the prop slip down a little and give you more hole shot and acceleration to top speed.

H

NJCinMN · Jul 14, 2009

Re: 1969 Merc 1000 Prop Question

hwsiii,
Excellent information. Wow I feel like I can make an informed decision now. Thanks so much. I'm leaning to the 15" but have read that this old motor I've got doesn't mind running in the 5500-5800 range at WOT. I'll post what prop I choose and the results. I've found the 14" here on iboats but they want a "boat-load" of money, ha-ha. Thanks again for your calculations.

hwsiii · Jul 14, 2009

Re: 1969 Merc 1000 Prop Question

I am glad I could help.

H

hwsiii · Jul 15, 2009

Re: 1969 Merc 1000 Prop Question

I wish I really knew which motors can run at those high RPM and it is good for them. Dhadley told me about the OMC, but I didn't know it applied to Mercury's as well. Were those speeds GPS.

H

NJCinMN · Jul 15, 2009

Re: 1969 Merc 1000 Prop Question

Unfortunately those speeds were not GPS. A friend's speedo said 33 mph...I think they're pretty close but I will be able to verify with a GPS next weekend. My focus is still on the RPMs. I'm guessing the speed will change the slippage calculation and then ripple through to the projected RPMs you gave with lower pitched prop. I'll verify speed on GPS before making any decisions or adjustments.

hwsiii · Jul 15, 2009

Re: 1969 Merc 1000 Prop Question

You are exactly right, when it is not real speed the numbers are not real either.

H

NJCinMN · Jul 27, 2009

Re: 1969 Merc 1000 Prop Question

Well I finally got ahold of a GPS. Here are the results...
Just me this time...no other gear or adults
Running 4400-4500 rpm @ 34 mph on the GPS. I did several runs and the GPS came back with almost the exact speed down to the tenth.

H, is the math still showing a 15" will probably be my best bet.
Thanks, Nick.

hwsiii · Jul 27, 2009

Re: 1969 Merc 1000 Prop Question

Nick, with then new numbers and you wanting to run higher RPM, in the 5,500 to 5,800 range I will recommend a 4 blade Solas Amita prop with a 13" pitch. It ought to run in the 5,400 to 5,600 RPM range when you are by yourself and with the 4 blades instead of 3 your prop slip will go down and when you put extra people in the boat you will lose very little speed, and it will come out the holeshot like a chettah just don't ram it to full throttle on take off as it will be straining the lower unit.
Please verify the lower gear ratio is 1.7:1, if that is wrong my calculations will be wrong.

Prop Change

My Prop Pitch formula does not take into account the 4th blade, whih will drop some RPM.
Depending on the RPM you get you might try raising the motor up one notch and moving it back into the transom by one notch as well to stop ventilation.

H

NJCinMN · Jul 27, 2009

Re: 1969 Merc 1000 Prop Question

Sounds good. I'll verify the gear ratio and then proceed. Just out of curiosity, what would you recommend if I stayed with a 3 blade?

hwsiii · Jul 27, 2009

Re: 1969 Merc 1000 Prop Question

In my opinion if you wanted a 3 blade in aluminum you could try the Turning Point Hustler.

H

NJCinMN · Jul 27, 2009

Re: 1969 Merc 1000 Prop Question

And that would still be a 13" pitch? Again out of curiosity, are you expecting that I'll lose 1-2 mph or remain the same? Thanks again, you've been more than helpful. I'll repost when I get the new prop and have results or if I find that the gear ratio is not in fact 1.7.

1969 Merc 1000 Prop Question

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