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Prop advice for a 90 yamaha two stroke on an 1988 montauk
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| jaxmyth |
Posted on 07/20/15 - 4:50 AM
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I just purchased a really clean 2005 Yamaha two stroke 90 to be installed on a 1988 Montauk. I've found some info through searching and realize there is a ton of info that is confusing me.
13" x 17" Yamaha Painted Stainless Steel
13-1/4" x 16" Yamaha Performance Series Three Blade
13-1/4" x 15" Stiletto Advantage 4.25
13-1/4" x 15" Turbo 1 4.25
This is the list that I've found here and on the other site. Tom seems to recommend the stiletto quite a bit, and I'm leaning towards that prop, but my question is, is the hole shot good with this prop? also should I see 40+ mph with this prop? I'm ready to pull the trigger now on buying, I just want to make sure I get it right the first time. I really would like to see 40+ if I can without sacrificing much hole shot. If this is the correct prop for my setup, where is the best place to purchase? Thanks for the advice in advance.-Jack
(changed abbreviated year to full 4 digit year for clarification)
Edited by Joe Kriz on 08/08/15 - 3:22 PM |
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| dauntless-n-miami |
Posted on 07/20/15 - 6:31 AM
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Hello yet again jaxmyth, What is the intended use of your 17 Montauk? What cargo loads (people, gear, etc.) do you expect to have from time to time.
Obviously there is a noticable difference between your Whaler and mine even thought we have like outboards.
I have run two props on my Dauntless 15 and have noticed differences between them. I typically boat with my family (4 of us plus snorkling gear, and cooler with treats). Our two kids are late teens so adult weights are in play.
My first prop was a Solas 13-1/4" x 17P (Round ear 3 blade) in Strainless Steel. The Round-Ear props are refered to as "Bow-lifting" style. Getting on plane promptly is not this props best trait, once on plane good mid-range to top-end. I try not to push beyond 5200 RPM's if not needed, MPH on GPS around 38 to 40 (with near perfect smooth chop) and with loads mentioned above. This prop gets off plane very quickly if slowing down while negotiating chop and swells!!!
My second prop (purchased used but in excellent condition) is a Power Tech 13" x 17P (Semi/Cleaver 3 blade) in Stainless Steel. This prop is refered to as a "Stern-lifting" style due to the semi-cleaver (shark fin) blades and is very similar to the Yamaha prop you mentioned in Black trim. I get "out of the hole" or on plane in half the time and with less engine effort than I did with the Solas having same loads. Mid-range to top-end pull is consistant, again I try to stay below 5200 RPM's but there's still throttle left for a 5500 push if I needed it. MPH on GPS is between 36 to 38 (with near perfect smooth chop) without pushing the Yamaha 90 hard.
I now keep the Solas as a back-up/spare for a "just-in -case" day. From your posted selections I viewed a few props with 15P, these are suggested?
Hope this helps...
Best,
Angel M.
1996 Dauntless 15, Sportsman Pkg. - 2007 Yamaha 90 HP 2-Stroke |
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| jaxmyth |
Posted on 07/20/15 - 7:23 AM
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Dauntless, thanks again for the reply. I mostly use the boat for fishing with two adults and coolers and fishing gear. but I do use it occasionally for cruising with my wife and two small kids. I don't normally have a heavy load in the boat and mostly cruise in the intracoastal and st johns river. i'd rather be able to hit 40 to outrun some storms in the river and maybe pull a tube with the kids.i won't be pulling any adult skiers out of the water or anything like that.
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| dauntless-n-miami |
Posted on 07/20/15 - 7:54 AM
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Sounds good, then perhaps the props with smaller 15" pitch will give you the low-end punch. I suspect with the size and weight of your Montauk and if looking for a 40 MPH running speed (when needed) you will eventually over-spin the 15" Pitch.
Is there a possibility with a local boat/prop shop you could do a "lend-lease" process to test the diameter versus pitch theory? Down here in Miami, FL we have numerous prop shops that will afford us boat owners this service and in turn they hope to gain a customer which I think is good business.
Do some research on the two types of prop designs Semi-Cleaver versus Round-Ear you may find the topic interesting depending on the weight distribution of your Montauk and if currently stern heavy.
Best,
Angel M.
1996 Dauntless 15, Sportsman Pkg. - 2007 Yamaha 90 HP 2-Stroke |
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| mtown |
Posted on 07/21/15 - 5:26 AM
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I have the 13.25x15 Stiletto Advantage on my 1966 16'7" with a 1989 Yamaha 2-stroke mounted 3 holes up.
It absolutely flies with an excellent hole shot. I now cruise at 2800 RPM and have been at 5100 and 43 MPH.
I have yet to run wide open but expect I would see 45. This prop and motor came on the boat, I did raise the motor. If I were to search for prop advise Tom is where I would turn.
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| Whalerbob |
Posted on 07/21/15 - 7:01 AM
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I have the Stiletto mentioned above on my 1989 with 1998 Yamaha 90 2 stroke (great engine btw). I carry a lot of gear and it's still mounted in the blind holes/all the way down but I'm only getting 4400 RPM and 31kts WOT with my average load.
I plan to re mount the engine but don't think it will make that much of a difference. I rarely need/want/have the opportunity to run faster than that but wonder if there's a governor/throttle adjustment I could make or if I just bought the wrong prop. I only gained a couple kts and rpms from my old aluminum.
Ps: how much did you pay for the engine. If mine dies tomorrow I'd be torn between a used 90 / 2 stroke vs 70 / 4 stroke.
Edited by Whalerbob on 07/21/15 - 7:32 AM |
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| jaxmyth |
Posted on 07/21/15 - 8:11 AM
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I'm trying to figure out the right height to mount mine also. I believe your issues will be the height that you have it mounted. I was hoping Tom w Clark would comment. I really hope the stiletto gets me the performance I want. I rarely have a heavy load in the boat. I ended up paying close to 5k for the motor, which is higher than I wanted,but the condition of the motor is impeccable. It was truly a freshwater gem. I would have loved to purchase a new 4 stroke 70 to replace my old 2s 70, but price was a factor.
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| mtown |
Posted on 07/21/15 - 8:52 AM
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I was a bit of a skeptic about the performance gained by raising the motor. It just didn't seem that it could change that much. I do not have apples to apples yet because while I have two identical hulls [1966+1964] the motors are a 90 Yamaha 2-st on the 1966 and the 1964 has a 70 Yamaha 2-st.
The 70 is the one I have been running for many years, and I did a lot of work on it this spring. It is now water ready and has the motor up to the third hole just like the 90.
If the added performance is anything close to the 90 I will be extremely happy. Hole shot is so fast, and I am now cruising at almost 1000 RPM less than I used to, and going faster. I believe the 70 is very adequate power for my boat, but the 90 is probably a better fit for the Montauk.
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| ursaminor |
Posted on 07/21/15 - 2:26 PM
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Jax,
I am running a 90 E-Tec on my boat so not apples to apples with your situation, however it replaced a 1989 90 HP "Mercaha" that was very similar to the engine you have. The old motor was mounted all the way down on the transom and would turn a 19" Solas aluminum prop to about 5000 RPM (over 3 years ago at this point so my memory is fading on the specifics) and 40-41 GPS if I trimmed it out enough. The 13.25 X 15" Stiletto acts much more like a 17" pitch prop, in fact the other prop that was recommended here when I repowered was the BRP 17" Viper stainless. The Stiletto has relief holes in the hub that help with the hole shot, if you have a healthy engine and not too heavy a load it should be a good match. Mount it at least two holes up, most here will recommend three holes up. It's a great all around prop on a 16 / 17 with a 90 HP engine. I've seen 43 GPS at 5200 RPM light load on mine, I'd be surprised if you didn't see similar numbers with yours. Good luck.
Edited by ursaminor on 07/21/15 - 2:29 PM
1989 Montauk 17 / 2012 90 HP Evinrude E-TEC |
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| Whalerbob |
Posted on 07/21/15 - 2:47 PM
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I could have this wrong but I think I read somewhere that each hole I raise the engine will gain me about 1000 rpm and 1.5 mph top end. I know it needs to be done but just haven't gotten around to it yet.
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| Phil T |
Posted on 07/21/15 - 8:27 PM
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WhalerBob -
The general guidance on raising the engine is for each hole the motor is raised, one would gain 250-400 rpm.
I personally saw an increase of 224 rpm for each hole raised (motor was a Yamaha F1150
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| Whalerbob |
Posted on 07/21/15 - 9:10 PM
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Thanks Phil, that's probably why I've been procrastinating this one. Is there another prop or anything else I can do to boost my performance? I gained about 2 kts with the Stiletto but this is pretty much how it's been since new.
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| jaxmyth |
Posted on 07/22/15 - 3:05 AM
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ok, so I've had to mount the engine using the blind holes so I don't have to drill new holes. does that mean the engine is all the way down? if so, instead of the stiletto prop, which prop should I get? I really do not want to have to drill new holes and plug the old ones.
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| jaxmyth |
Posted on 07/22/15 - 5:01 AM
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I guess basically what I'm asking is, instead of drilling new mounting holes, what would be the most appropriate prop to get with the best performance given the current holes that I'm using. "blind holes are being used" and the anti cav/ventilation plate is even with the keel.
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| mtown |
Posted on 07/22/15 - 5:41 AM
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If you read the old thread I re-posted you will see that I was also hesitant to drill the holes and raise the motor. It probably took an hour total time the first time.
On the second boat it was probably 15 minutes. By myself both times, although I did use a Bobcat with a cable to the hoist ring built on the motor the second time. Used a thick epoxy fairing compound for the old holes, but as others have said a dowel soaked with resin would be fine.
I predict when you do it you will be amazed and your only regret will be not doing it sooner.
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| jaxmyth |
Posted on 07/22/15 - 6:32 AM
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Mtown, do you have any pictures of your install? and you're using the third holes down in the top set of holes?
Also, I tried to order the stiletto advantage 1 prop from boatownersworl.com and they don't have it anymore. I called dansprops to see if he had it and was told he would have to check with his distributor and that he'd call me back. but I never received a call. are there any other places to get that prop if I do re drill the holes?
Edited by jaxmyth on 07/22/15 - 6:36 AM |
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| dauntless-n-miami |
Posted on 07/22/15 - 8:15 AM
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Hello jaxmyth, there is one option if you really prefer not to re-drill the transom. You could consider a manual "jack-plate" with minimal set-back (4 inches or less if available). If this seems reasonable you would need to research for a model/type which may have your current bolt-hole configuration or re-drill the 2 lower holes into the jack-plate to match your transom.
This was just a thought. It offers ease of height adjustments and without having to fuss and re-seal mounting bolts through the transom if doing further height adjustments. I wish I would have done this when I had my outboard dismounted sometime back. I will definitely consider this method and with hydraulic steering the next time my motor comes off. I've seen some reasonable prices on ebay if this helps.
Happy boating...
Angel M.
1996 Dauntless 15, Sportsman Pkg. - 2007 Yamaha 90 HP 2-Stroke |
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| jaxmyth |
Posted on 07/22/15 - 8:42 AM
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Ok. well it appears as if I need to just plug the holes and redrill. what type of plug should I use to fill the holes with and what epoxy? also, when I redrill, do I put the motor on the transom with the top two bolts in the bottom two holes of the top four in the motor and then drill which hole in the bottom?
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| Whalerbob |
Posted on 07/22/15 - 2:33 PM
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jaxmyth wrote:
Ok. well it appears as if I need to just plug the holes and redrill. what type of plug should I use to fill the holes with and what epoxy? also, when I redrill, do I put the motor on the transom with the top two bolts in the bottom two holes of the top four in the motor and then drill which hole in the bottom?
If I understand what you're saying that's how I planto approach it.
1) take motor completely off and I would pack the hole with fiberglass matting soaked in epoxy, gelcoat, and sand smooth.
2) mount the engine on the transom using the top two bolt holes at the desired height and use the mounting holes of the engine as my guide/template for where to drill the bottom holes. (I don't have the diagram in front of me but I think I am going for the green holes so they are as high in the splash well as possible.
3) remove the engine, blob marine silicone in the holes then replace the engine and bolt everything tight.
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| mtown |
Posted on 07/22/15 - 3:26 PM
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Jax
sent a PM . Will send pics but cannot post here. No outside account for that.
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