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Author Topic:   jack plate settings, 15 sport
trainer posted 03-27-2002 10:11 PM ET (US)   Profile for trainer   Send Email to trainer  
I just had a CMC (cook) manual jack plate installed on my 89 15 with a yamaha 70. It has a 5 1/2 set back and 5" travel. Is the 2/1 ratio, back to up, a good starting point?

Flipper posted 03-27-2002 11:17 PM ET (US)     Profile for Flipper  Send Email to Flipper     
That's a good start, I did the same -and then raised it until I felt vibration at high speed and/or had cavitation while planing.My ideal setup (for the prop I have)ended up being about 31/2" up. Above this height, in my case, there was excessive vibration at high speed.
Clark Roberts posted 03-28-2002 06:03 AM ET (US)     Profile for Clark Roberts  Send Email to Clark Roberts     
Flipper, the ratio you mention (back 1 up 1/2 )seems to hold up in most cases... my 15 now has a 70 Merc back 5 and up 4... way too fast! Watch that cooling water flow as you raise engine! happy Whalin'.. clark.. Spruce Creek Navy!
Bigshot posted 03-28-2002 11:37 AM ET (US)     Profile for Bigshot  Send Email to Bigshot     
What the hell are you guys talking about? I did not know manual jacks had ratios, thought you just turned the screws like I do.
where2 posted 03-28-2002 04:25 PM ET (US)     Profile for where2  Send Email to where2     
I think the concept Clark is describing is with a 5" setback, he can jack the cavitation plate 4" above the bottom edge of the hull. Flipper says he's got 3-1/2" above the bottom of the hull, so they're saying 1" setback allows you to jack the engine 1/2".

My 70Hp OMC is straight bolted to the hull... 50mph feels way to fast that way too! Last time I was out, I was playing with the PTT seeing just how much rooster tail I could throw doing a measly 25mph. (Since that's what the speed limit allows me to run in the ICW).

trainer posted 03-28-2002 10:31 PM ET (US)     Profile for trainer  Send Email to trainer     
Today I got the boat back in the water and it flies with the jack plate and a new gelcoat on the botton instead of the rough bottom paint. With the motor raised 3.5 inches I have good control at 42 mph (gps), however with the trim out just a little more there is very little boat in the water and very little control of steering. With the motor jacked another .5" there is a lot of chine walking.
An interesting note: same boat with 50hp yamaha ss prop WOT 5200 rpm 32mph, with 70hp yamaha SS prop WOT 5500 rpm 36 mph, with jack plate (70 ss) WOT 5800 rpm 44 mph.

thanks for the help

Alan Hiccock posted 03-28-2002 11:05 PM ET (US)     Profile for Alan Hiccock  Send Email to Alan Hiccock     
Ive got a 15 sport with bottom paint and a 70 Yammie { 50 hrs } turning a 13x19 aluminum , was clocked by a buddy 45mph today {on a speedo}. I orderd a Stiletto 13.25 X 19. From Overtons Tues. {hope to get my new toy tommorow and do 47 mph's.}
What size prop you turning? With no b.paint I would think you should maybe do better then 44 with a ss prop, no?
Am I just being too optimistic?
Thanks for any feedback, Alan
trainer posted 03-29-2002 12:50 PM ET (US)     Profile for trainer  Send Email to trainer     
I am turning a Yamaha 13x19 ss. With the jack plate I get 5800rpm. This is close enough to top end rpm (6000) range for me. I am not sure that I want to go any faster than 44.5 mph (gps). At that speed the 15 is not very stable. I don't think there is much of the boat left in the water over about 42mph. It is fun to go fast enough to make your eyes water though.
Alan Hiccock posted 03-30-2002 10:21 AM ET (US)     Profile for Alan Hiccock  Send Email to Alan Hiccock     
I just got myt Stiletto delivered today YEAH!!
Its wild up there with this boat in the 40's I concur, Big destroyer steering wheel, wooden thwart seat with no windshield, Im gonna install my 13.25 X 19 today and haul ass!!
Bye, Alan
Flipper posted 03-30-2002 09:18 PM ET (US)     Profile for Flipper  Send Email to Flipper     
Alan,let us know of any increase in facial air pressure-I may want a Stiletto in my arsenal.
Alan Hiccock posted 03-31-2002 09:31 AM ET (US)     Profile for Alan Hiccock  Send Email to Alan Hiccock     
Ive got to return it, was a little to bummed to post anything after having to go through all the trouble of taking off old, finding out it was way off then putting back my worn out aluminum ect.
Stilleto it seems are very agressive with thier cups, rake ect.
My 13 X 19 Stock Yammie aluminum gave me 6000 WOT @ atleast 45 mph's { or very close}.
Yesterday when I installed this Stilleto I got 5200 WOT after trimming the sh*t out of it { my op. range is 6000-7000 70 HP} .
It planed terribly, the boat wasnt " lifted" out of the water enough, I took it right off and will box it up & send it back to Overtons tommorow.
Im debating on weather or not to try another Stiletto { I think 2 sizes down to 13 1/4 X 16 with this type rake, cup ect.}
I'm leaning towards just getting my $ back and buying another stock Yamaha aluminun, heck can buy 3 aluminums for the price of this Stilleto SS.
Thanks for the intrest, Alan
Flipper posted 03-31-2002 08:54 PM ET (US)     Profile for Flipper  Send Email to Flipper     
Alan, that's a drag.Maybe the extra 1/4" of diameter is bogging things down. That prop sounds like it's designed for a jackplate setup, or a jacked up motor.You may still need to pitch down, even then.
I have a 26" pitch Laser2 on my Merc 90 and it's only turning 5400 rpm wot.I thought once I got the jackplate I would get some extra revs, but this prop is wide,lofty and cupped out.All I got from jacking it way up was vibration (it likes breaking the surface, but not too much).I'm still getting 55-56mph the way it is set up now, but I'm forever curious to see what an extra 200-300rpm's would yield.I may get this prop pitched down 1"; if I get bored.
The right stainless should help things;if you try another one, let us know how she goes!
Alan Hiccock posted 04-01-2002 10:21 AM ET (US)     Profile for Alan Hiccock  Send Email to Alan Hiccock     
A drag is a good way of putting it.
With mailorder you have to pay shipping @ $ 18 bucks for this hunk of steel. I suggest going to your local prop shop or marine discount store when propping a boat.
Ive been in this " boating game" for years and have been down this block before with other boats, maybe one day I'll try another SS but for now I'm a little beaten up from this deal & am sticking with my Aluminiunimiunmimunmmium { spelling might be a little off there}, Alan
Bigshot posted 04-01-2002 11:03 AM ET (US)     Profile for Bigshot  Send Email to Bigshot     
Try the 17" Alan. It should bring you up to around 5600rpm which is good. I would also look for a Yamaha OEM 13x19" on E-Bay, she should get you 5700+. I have noticed that OEM props usually work the best.
Alan Hiccock posted 04-01-2002 05:01 PM ET (US)     Profile for Alan Hiccock  Send Email to Alan Hiccock     
Bigshot, I think your right about using OEM props for closer/easier matches, I bet if I tryed another Stiletto the 15" P. would give me my 6k. Figure I was juust getting 5400 with the 19. Well its a start now I know what sizes are closer in SS if I get another, was at the postoffice returned the SS today 9 bucks from LI, NY to NC. Payed 16 to have it shipped so wasnt too bad. Looks like the girlfriend wont be having any beer tonight , that's all.
Flipper posted 04-01-2002 09:32 PM ET (US)     Profile for Flipper  Send Email to Flipper     
Alan, have you ever come across a marina that lends out used/traded in props? I was lucky to find a marina that does just that.I was able to try out three props and that's how I got my Laser2.I haven't heard of this service anywhere else up here, maybe in your neck of the woods?
Alan Hiccock posted 04-01-2002 09:54 PM ET (US)     Profile for Alan Hiccock  Send Email to Alan Hiccock     
My marina has just started selling Yammies, before that OMC's. The owner used to let me " play" with the prop dept. till I was satisfied with one when I had my Johnsons.. He's just starting to carry the Yamaha props.
I do know plenty of other folk in the biz you make a good point. No more mail order for now.. from what Ive learned most prop dealers/shops are pretty good with letting you try one out as long as you dont take it out on a rock or something. Tides have been EXTREME off Long Island as of late so I'm going to continue to run my tattered Aluminum for now. It's amazing what I did to this new prop in 20 hrs.! Well all it takes is 1 soft grounding into the mud @ 20 to pretty much wipe out a stock prop.
Flipper posted 04-02-2002 12:12 AM ET (US)     Profile for Flipper  Send Email to Flipper     
Alan,yeah I guess hard water calls for a softer metal!No tides in our part of the St. Lawrence,just the odd "Poker Run Swell".
I forgot to mention the props I borrowed were non- stock exotics (choppers,etc.),ones that people order and are stuck with.The chopper was fun, but the hole shot was bad (as expected) and I could feel the hull skip to starboard while crossing wakes at speed.Yikes! Borrow at own risk!
Bigshot posted 04-02-2002 10:47 AM ET (US)     Profile for Bigshot  Send Email to Bigshot     
That is why I hate alum props. i do my share of dredging and the alum will ding on the slightest bump. I have never(knock on wood) blown a lower due to SS props. I just had a 17' SS OMC rehubbed for my Zuki and will see how she performs.
Alan Hiccock posted 04-02-2002 02:55 PM ET (US)     Profile for Alan Hiccock  Send Email to Alan Hiccock     
I did, take out a lower unit with an SS prop that is.
Was doing the "Old man" we call him {owner of my marina} a favor as he gives me full run of the shop ect..
3 years ago, mid January, freezing rain, towing a customer of his to the boat ramp where the floating docks were removed for the winter & it was a newly installed ramp I never been to.
This guy was doing a tap dance on the sloping bow of his Bayliner as I was trying to get him into this small notched out boatramp with 20 knot winds in a big Channel.
I after couple attempts pushed him in there found my stern real close to the bulkhead put it in gear juiced it a little and hit a slab of concrete with an almost new 90 Johnson. The engine came out of the water, I hit it pretty hard but kept running and I really didnt think there would be more then prop damage.
The prop had some nice notches { like the size of nickles, boat got me home but the spline twisted. We took apart the lower unit & it was shot, Owner payed for a new one but I can honestly say that I'm a nimrod { I mean Captain} that took out a lower unit with a SS prop. It was extreme circumstances & I was working with the boat, you just gotta stay away from the big rocks and such.
Its pretty hard to do for most people who boat in my area though. Kind of a freak thing, Alan
Bigshot posted 04-04-2002 10:28 AM ET (US)     Profile for Bigshot  Send Email to Bigshot     
OK I did ruin a lower unit twice.

I wore out the LU on my 1982 35hp Johnson with an alum prop. I did more dredging than you can shake a stick at. I think I walked that boat more than drove it.

In 94 I got a new 20 Hydra sport. I took my parents out for a ride in early April(in NJ and we headed for the Causeway bridge. We were in the channel and "BANG"! I looked at my father and we were still going 30mph. We tilted the engine and the skeg was sheared and 1 blade missing off the SS prop, shaft was bent and the other blades were twisted. It made it back home(5mi) and then back to dealer (7MI) like that. Insurance paid for a new lower and prop.....only had 14 hours on the old one. We hit a submerged DOCK that was floating about 2' down in the channel. It would have done the same with an aluminum prop.

Like isolated case.

Alan Hiccock posted 04-04-2002 12:46 PM ET (US)     Profile for Alan Hiccock  Send Email to Alan Hiccock     
Ya live long enough & everything happens to ya! ha haha Between my bikes, vettes/hotrods and boats and crazy ex- wife and girlfriends, dont know how I aint dead .

2 days ago I had the Whaler out the inlet Jones here off S. Shore LI.
I was trolling a Yourzi lure just off the jettys & beaches in honest 2& 1/2's . It was just me and the Coast Guard practicing manovours. They came over to me shaking thier heads like I was nuts for being out there in a 15 sport, from a distance these boats look even smaller. I felt really comfortable and it's wild how close to the water you feel with these low gunnels, man I was disappearing in the swells. Feel comfortable with this boat to go couple miles out the inlet in all directions on nice days, with the 70 if it kicks up I'll be back inside within couple minutes.
later Capt., Alan

trainer posted 04-05-2002 09:35 AM ET (US)     Profile for trainer  Send Email to trainer     
I checked the yahama specs for my 02 70 and the opt rpm range is 5000-6000. Be careful if you are trying to get 6-7k.
I am turning a yamaha 13x19 stainless and the boat screams. Go stainless, its worth it.
Alan Hiccock posted 04-05-2002 02:03 PM ET (US)     Profile for Alan Hiccock  Send Email to Alan Hiccock     
Ive got the same motor, no I'm not trying to get 6-7K { dont remember saying that but ment 6k. & also theres a rev limiter.}
I today as matter of fact bought another stock aluminum 13 X 19 prop @ a yammie dealer. They wanted 400 bucks for the 13 x 19 SS, what did you pay for yours ?
Bigshot posted 04-05-2002 02:36 PM ET (US)     Profile for Bigshot  Send Email to Bigshot     
Alan keep checking E-bay....they are there for around $150.
Alan Hiccock posted 04-05-2002 05:10 PM ET (US)     Profile for Alan Hiccock  Send Email to Alan Hiccock     
Thanks for the tip Bigshot. As you mentioned once before the stock Yamaha OEM jobbie should match better.
Ive been going through aluminums 1 a month so far this year & its only April!
There were exceptionally low tides off Long Island last couple weeks.
Bigshot posted 04-08-2002 11:22 AM ET (US)     Profile for Bigshot  Send Email to Bigshot     
You can have them repaired for about $25. i had some extensive welding done to one and it was $28.
Alan Hiccock posted 04-08-2002 11:27 AM ET (US)     Profile for Alan Hiccock  Send Email to Alan Hiccock     
I was thinking about that last night, its not too bad just looks like the diameters about 1 " less and cup if any is history.
Ive got a few hour to kill before tide comes in gonna check prop shop today, thanks, alan

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