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  Jackplate, 90 Yami, prop

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Author Topic:   Jackplate, 90 Yami, prop
Montauk posted 11-13-2002 08:50 PM ET (US)   Profile for Montauk   Send Email to Montauk  
I recently installed a CMC Hydraulic jackplate on a 1973 Montauk powered by a 90hp yamaha. It is installed for maximum lift and at the highest position the water pressure gauge reads 17psi at 4000rpms. Prop is a 13-1/4 X 17 aluminum 3 blade and it will get on plane with one person and carefull throttle aplication. With the jackkplate down, the performance is great out of the hole, and it runs about 5500rpms- 43 MPH. I would like to go to a stainless Yamaha performance series prop and the smallest they make is a 4 blade, 13-1/4 X 18. Is anyone running a similar set up and if so what prop and RPM's are you running? This motor runs 4800 RPM's and 46 MPH with a 19 pitch stainless but does not hold plane at slow speeds. I am not concerned with being fast, but I want it to get out of the hole fast with the motor raised for skinny water and stay on plane at slower speeds. Thanks
Bigshot posted 11-14-2002 10:15 AM ET (US)     Profile for Bigshot  Send Email to Bigshot     
My experience is go with the 17" Stainless OEM Yamaha prop. They are already kinda cleaver shaped so that they can pierce the surface. Have the prop double cupped if you are blowing out at all.
John W posted 11-14-2002 11:06 AM ET (US)     Profile for John W  Send Email to John W     
I'm not fond of the black 3 blade stainless Yamaha "cleaver" type prop on my Yamaha 115...it's given me blow-out problems in turns without the motor on a jackplate or in a high setting. In general I'm unimpressed with Yamaha props.

Power Tech has excellent 4 blade stainless props made for smaller motors like yours, they'll hold on at high jackplate settings & perform well for what you're looking for. You will give up a couple mph with a 4 blade though. A 4 blade will also generate less prop torque...prop torque can cause a heel to port and steering pull on some boats.

Bigshot posted 11-14-2002 11:17 AM ET (US)     Profile for Bigshot  Send Email to Bigshot     
See I have had the exact opposite with them, Mine handled like it was on rails....C'est la Vie I guess.
lhg posted 11-14-2002 02:32 PM ET (US)     Profile for lhg    
For elevated running on the flats with your rig, you want the Mercury Trophy Plus 4-bladed prop in 17" pitch (no higher). These can be ordered with interchangeable hub for Yamaha, and will be a real screamer for your setup. An aluminum prop is totally unacceptable for your described application.
A performance SS prop will be a HUGE improvement.

These lower pitch versions were specifically introduced for the 90HP range engines, when run on jack plates, in bass and flats applications. You won't have to drop her down much for acceleration, and these have great hole shot and mid range performance. One will set you back about $415 however. Because of the huge "bite" these things take on the water, you don't want to go any higher in pitch. You'll still probably lose some top end rpm's. These propellers are designed to be run about 2" high or more, but you have to watch your water intakes. Running them fully submerged increases effective pitch by at least 2". These props also have the 4 vent plugs, where you can fine tune them for ventilation slippage on acceleration. They hang on to the water like glue, and just don't ventilate at all in rough water, etc.

Montauk posted 11-14-2002 03:46 PM ET (US)     Profile for Montauk  Send Email to Montauk     
Thanks for the replies. lhg, what boat/motor combo do you run the merc trophy plus on? Bigshot, are you talking about a 4 blade stainless yami prop?
Anyone out there running the same combo I am?
Montauk posted 11-14-2002 03:51 PM ET (US)     Profile for Montauk  Send Email to Montauk     
I have a chance to buy a used 13-1/4 x 18 Yamaha Performance 4 blade for half price of new and the seller had it on a 70hp yamaha/sakonnet and states it pulled 5400 rpm's. Hoping to find someone who has tried this combo.
Bigshot posted 11-14-2002 03:57 PM ET (US)     Profile for Bigshot  Send Email to Bigshot     
Try it, should be fine then. I was talking about the 3 blade which has cleaver type blades.
lhg posted 11-15-2002 04:45 PM ET (US)     Profile for lhg    
I think the Yamaha prop sounds like the right style, but I'd be concerned about the 18" pitch if your 17" aluminum is giving you max RPM's. The Sakonnet 16' hull is the same as your early Montauk hull, but I'm betting your max RPM's will be more like 5000-5100. For Mercury's part, they ALWAYS say to drop down an inch in pitch when switching to 4 bladed flats/bass props like this. Aluminum props will always carry more RPM's, because they are light to spin, do not have a progressive blade design, and flatten out a little under load, reducing pitch.

But for the price, you could have the Yamaha reduced 1" in pitch (maximum they can do with performance style SS) if necessary.

You might also see what Stilleto offers in 4-bladed props for your engine. I think they're about $325 in 4 bladed design, and they may make a 16" or 17" pitch model.

Montauk posted 11-16-2002 08:24 AM ET (US)     Profile for Montauk  Send Email to Montauk     
lhg,
According to the seller of the prop it is not the cleaver style, so at this point I am going to continue the search. I assumed wrongly that it would be a cleaver style. Ice is forming on the lakes here so I have untill Spring to get this figured out. The boat just has to be ready for my spring fishing trip to FL.
John W posted 11-18-2002 10:21 AM ET (US)     Profile for John W  Send Email to John W     
I'll repeat, in my opinion, YOU DO NOT WANT A CLEAVER STYLE YAMAHA PROP for running with a jackplate at high settings. The black Yammie cleaver props are a max speed type prop & they do not hold on at high jackplate settings or in sharp turns, depending on the boat & setup, of course. Holeshot is uninspiring as well. You will get much better performance with one of the 4 blade props suggested, but if you don't want to spend the cash on one of them, a 3 blade cupped Stilleto or similar will perform better for what you're looking to do than the black Yammie prop IMO. Just my opinion, but it's based on owning that prop & trying several others on a Mako 17 with a Yamaha 115. Granted, I'm testing on a different boat & motor, so the Yammie prop will behave differently on your rig. But what I'm trying to achieve is the same...hole shot & midrange performance in shallow water. The best performance I've found was with the Power Tech 4 blade 15 pitch prop, which sounds very similar to the Merc prop suggested above.
Montauk posted 11-18-2002 12:24 PM ET (US)     Profile for Montauk  Send Email to Montauk     
John,
I agree with you on the black SS yamaha 3 blade cleaver style prop. I have a 13-1/4 x 19 that I already tried with the jackplate set high and it did not perform as well as the 13-1/4 x 17 cleaver style alum. prop. However, a surface piercing, or cleaver style is what is needed for running the jackplate on a high setting, not an elephant eared type prop. I am looking for a mercury trophy plus or similar 4 blade prop in a 13-1/4 x 17. I have until March to have the boat ready for fishing so am looking for used until then, if none to be had used ,I will buy a new one then.
John W posted 11-18-2002 03:47 PM ET (US)     Profile for John W  Send Email to John W     
Montauk, let me state up front that I make no claim to be a prop expert. But I disagree that you want a cleaver type prop for what you're trying to do. A true surface piercing cleaver prop, designed to be run at surface piercing jackplate settings, will give you max top end speed. It will need to be higher pitch as it's not designed to run submerged. Such a setup will give lousy holeshot & midrange performance, but will give max top speed. This is the type prop setup you see on Arneson surface drives, etc., and they're pitched to not be submerged at planing speeds. If you were to try to run a true surface piercing setup on your outboard, my guess is you would need a low water pickup to make it work. And a high pitch surface peircing cleaver prop would be worse in midrange handling, slow planing performance, & holeshot than the prop you have now.

A cleaver is not the type of prop you want for your described uses IMO, that is holeshot, midrange performance, & keeping a boat on plane at slower speeds. These newer 4 blade rounded blade props made for midsize motors are designed primarily for flats & bay boats to accomplish what you say you want. They are not designed to be max speed, surface piercing props, but rather to hold on in turns & in a chop despite higher motor settings.

Check out the online catalog at www.ptprop.com . I have tried the "Accelerator Series Holeshot & Handling Prop" with excellent results & will buy it as soon as it's in the budget. They also have a "Flats Supercup for Extreme Motor Elevations" prop that I have not tried. Neither of these is a cleaver style prop.

I've seen "Turbo Flats IV" props advertised for midsize motors on flats boats...they're not cleaver style props. I don't believe the Merc Trophy 4 blade prop mentioned above is a cleaver style either. If you still don't believe me, go to a prop shop & try a yamaha cleaver vs one of the props I'm talking about.

lhg posted 11-18-2002 06:01 PM ET (US)     Profile for lhg    
It sounds like we have some confusion here on prop definitions. Nick indicated that the basic Yamaha elephant ear SS teflon coated props are "kinda cleaver shaped", setting this discussion off on the wrong track, or at least interpretation by some. But they are not cleaver props, and are not recommended for elevated operation. The Yamaha 4-bladed bass boat prop being considered, and the recommended Mercury Trophy Plus that is being discussed here, are also not cleaver props. John W is correct that TRUE cleaver props are not appropriate. Mercury defines them as racing props, for tunnel syle boats requiring stern lift to keep the bow from blowing over at speeds exceeding 90 mph. I can't think of any Whaler where a cleaver prop would be appropriate, no matter how overpowered!

Some very basic thoughts on appropriate props would be:

If your Whaler will not do over 30 mph, an aluminum prop will suffice.

If your Whaler will do 30-40 MPH, a standard SS prop is properly recommended for max performance.

If your Whaler will do over 40, a "performance" style SS prop should be considered, with a little engine lift of 3/4". Most of these props will increase bow lift, ride, holding, and generally improve overall performance of the boat.

If you want to run at engine heights of 1 1/2" or more, a performance prop is mandatory, assuming your engine can handle the higher pitch these props typically come in.

Availability of props, particularly by your engine manufacturer, gives you a clue as to what they think you should be running, and how high the engine could be set on the transom. For example, with Mercury, and mid range 75-125 HP engines, they don't make the performance props less than 20" pitch, except for flats boats, where height predominates over speed.
So with one of these Mercury engines, if your boat can't turn 20" in pitch, you shouldn't be running an elevated transom height, and should be using their Vengeance line of SS prop instead. Montauk's "flats" application would be an exception here, where height is more imprtant, necesitating a surfacing prop at slower top speeds. That's why they make the 4-bladed Trophy down as low as 17" in pitch.

John W posted 11-19-2002 09:51 AM ET (US)     Profile for John W  Send Email to John W     
lhg, we're saying the same thing, you're just saying it better. What I meant in my post is that unless you are running a true racing, high speed surface piercing cleaver prop, designed to be run with half the prop out of the water (which is not appropriate here), you DON'T want a cleaver-shaped prop like the black Yamaha props if you're using a jackplate or have a high motor setting.

Why? Because "cleaver shaped" props like the Yammie tend to have less cup than what can be put in round edged props...and the relative lack of cupping compared to other prop designs causes the Yammie style "cleaver shaped" props to blow out at high motor/jackplate settings, in rough water or in turns.

What you want for this application is 4 blade, max cup to PREVENT ventilation at planing speeds, despite the high motor settings. And props designed with max cupping such as the Power Tech props I mentioned and the Merc Trophy prop you suggested all have rounded blades, not "cleaver looking" blades. So if Montauk is out there looking for "cleaver looking" props he's making a mistake in my opinion.

I disagree somewhat in your statement regarding using Merc's prop suggestions as the answer to what prop you should be running, at least in regard to Montauk's situation. Flats boats & bay boats running jackplates is a fairly new phenomenon, and still only represents a small fraction of the boating public. For most boaters (who aren't running a jackplate), best all-around performance will come from the typical 3 blade stainless Stilleto/Rapture type prop, and they'll give several more mph at top speed than the 4 blades will. Merc, Michigan Wheel, etc aren't focusing on those running a midsize engine on a jackplate, since it's such a small % of buyers.

The prop makers I mentioned in my previous post are focusing on midsize engines for flats boats with jackplates. Turbo Propellers' "Flats IV" prop is available down to 13 pitch for midsize motors, and the Power Tech props I suggested are available down to 14 pitch. I personally doubt that Montauk's 90 hp will be able to turn a 17 pitch 4 blade Merc Trophy, it likely won't give him enough rpm's. But that doesn't mean that a highly cupped 4 blade prop won't give him the best performance for what he's looking to do...it just means he needs less pitch. Montauk, try the Power Tech or the Turbo in 15 or 16 pitch...I'll bet you'll like it.

Bigshot posted 11-19-2002 01:47 PM ET (US)     Profile for Bigshot  Send Email to Bigshot     
Larry, I meant they are cleaver type, not quite elephant ear like a standard alum or SST. They do have a flat trailing blade. Adding a cup is easy to do and usually free at General propeller. As far as talking about Montauks with Jackplates, I think it really depends on manual or hydraulic. My engine is high but it runs like she is 1" off the transom. I have NO blowout issues. Now if you have hydraulic and are lifting the thing out of the water, basically gonna be trail and error yet everyone I talk too or have ridden on their boat, has blowout when jacked to the hilt. They will run redline and only do 30mph but it gets them across the flats. Once in deeper water they lower it an inch or two, she grabs and takes off.
Montauk posted 11-19-2002 09:52 PM ET (US)     Profile for Montauk  Send Email to Montauk     
Bigshot, I think you hit the nail on the head! My jackplate is hydraulic, and what I am looking to do is maintain the power out of the hole that I have with the plate down and improve the hole shot when on the flats. I am running 5500rpm's with the jackplate raised slightly and the trim at the lowest setting, so if I trim the motor at all it will easily run 5800-6000rpm's which makes me believe a 4blade 17 pitch would run in the reccomended rpm range. I am not able to go to a dealer and try props because none in this area carry the type of props we are referring to. I do appreciate the education the three of you have given me on this subject and feel I am getting closer to solving the prop problem. I realized when I installed the jackplate I would have some trial and error issues to deal with, but the difference in handling, ride and skinny water ability has amazed me so far. The Montauk with a Hydraulic Jackplate is a far more versatile boat than most people realize.

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