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Author Topic:   1985 Montauk 17 and Johnson 115

Slick 50 posted 09-10-2009 06:45 PM ET (US)
Yesterday my 22 pitch OMC Raker came in so it was time to take the [1985 Boston Whaler MONTAUK 17 with 115-HP Johnson motor] out for a run. My son and I grabbed a few drinks and filled the boat up with fuel for a test spin.
With a calculated 950 pounds for the Montauk and an additional 1050 pounds of engine, fuel, gear and people, that adds up to about 2000 pounds.
My original thought was the 22 Raker would be too much prop but it turned out to be pretty close. I plan to run a 21 pitch Michigan Wheel Raptor and also a 20 pitch OMC Raker for comparison.
The original run of the 2003 115 HP Johnson was with a 17 pitch OMC SST propeller, the engine would easily over rev. This 2003 115 Johnson is a 2 stroke Bombardier carburetor 105 cubic inch engine. The engine is mounted on a 2.5 inch setback with the anti-ventilation plate about 3 to 3.5 inches above the keel of the boat. During the initial out-ting the SST did not blow out in turns but during the second out-ting the Raker would. I thought that was very strange. This Raker is the first edition Raker, not the series 2. I would consider dropping the engine one hole if this prop turns out to be the best choice???
The first WOT run turned out a 49.7 MPH at 5300 RPMs.
The second run turned out a 48.9 MPH at 5200 RPMs.
The third run turned out a 49.5 at 5300 RPMs.
From this information, is there a better prop choice or engine mounting set up? I have a 5.5 inch CMC hydraulic jack plate I could put on but didn't due to weight. The hub kit for the Raptor should be here any day so I can test it. The 20 inch Raker will be here tomorrow.
I feel the Montauk will break 50 MPH with just me in the boat along with less fuel, the 27 gallon tank was full.
Any help and ideas would be great.
Rick
ratherwhalering posted 09-12-2009 02:14 PM ET (US)
Rick, with the engine height and the problem with venting, I think you could try the Stiletto 13.25 x 19 Advantage I. Those Stilettos really like to run at higher settings, resist ventilation, and allow less drag from the lower unit as a result. My experience with these props makes me think it will run more like a fictional 21-inch Raker prop, and better than the Raptor 21, thus allowing higher RPM and better mid-range performance. Furthermore I think the 20-inch Raker (assuming it is not the 2-series) will have the same venting problems but allow you more RPM, however I doubt your top end speed will increase. I am interested in your thoughts and results.
--Rob--
Slick 50 posted 09-12-2009 09:52 PM ET (US)
Hi Rob,
Thanks for your help. The Stiletto sounds like a good one. I will keep my eyes open for one. The ability for it to run shallow sounds like the ticket. With the engine turning the Raker 22 to 5300 RPMs with a average load, do you think the 19 Stiletto will do the job? I like your thinking about running a 19 for great bottom end and mid range.
The 20 inch Raker came in today but was unable to run the boat due to water getting into the lower unit.
This is a used unit that was just put on a couple weeks ago. I did change the oil on it when it was installed but after 2 runs it was found to have water in the oil. Today the new seals were installed and the lower unit is back on the engine.
Tomorrow if the weather will clear up I can take the boat out again. The hub kit for the 21 Raptor is in the mail.
The 49 MPH runs with the 22 Raker were in rainy weather, 92 degrees and at MSL. The speed was registered on a hand held Garmin GPS. Speeds were noted going against the tide and with the tide.
ratherwhalering posted 09-12-2009 11:36 PM ET (US)
Rick, I think the Raptor-21 will be pretty darn similar to the Stiletto 13.25 x 19 with regard to performance. Both have aggressive cupping and rake. Let's see the performance results. If the Raptor is running at 5400 RPM (my pencil estimate) and doesn't vent, I think you have found your prop. If it runs low RPM or vents, then maybe try the Stiletto. Before running out and buying a Stiletto, lets wait for Clark to chime in, he's really got a better understanding of the variety of props available and individual characteristics than I do.
ratherwhalering posted 09-12-2009 11:40 PM ET (US)
I know I just contradicted my earlier post, and I actually think the Stiletto would be a slightly better prop, but in retrospect I don't think the difference between the Stiletto 19 and Raptor 21 will be significant enough to justify the expense unless there is a poor performance report from the Raptor, which I don't really expect.
Slick 50 posted 09-13-2009 01:10 AM ET (US)
Rob, this is all good. When I receive the hub for the 21 Raptor I will run the boat and report the results.
Your experience is a great help.
Thanks
Rick
Tom W Clark posted 09-14-2009 12:59 PM ET (US)
I've never heard of a propeller model called Raptor. Perhaps you mean a Michigan Wheel Rapture?
I have never but an Advantage against a Rapture in a same-boat/motor test so I'm not sure how it will play out.
One nice thing about the newer Rapture props is they also use the square bore hub kits like Mercury, Stiletto, Turbo and some PowerTech models.
Once you own the hub kit for your motor you can try many of those other propellers as well.
Slick 50 posted 09-14-2009 10:54 PM ET (US)
Tom, you are correct about the Michigan Wheel prop. I guess I should look at it a little closer. Do you have an opinion why the Raker ventilated easier than the old style SST?
The hub kit should be here later this week and the Montauk will be taken out for another test run. As mentioned, maybe a Stiletto Advantage will be next?
I had bought a Northstar F210 fuel meter late last year but it quit working after this first use. I have been in contact with Navico Technical Support (Northstar) about replacing the faulty sender, no luck. I bought another sender this week and hopefully we will have fuel flow indication.
Rick
Slick 50 posted 09-16-2009 06:58 PM ET (US)
Little update on the 1985 Montauk/2003 Johnson 115.
The hub kit for the Michigan Wheel Rapture came in today. The 21 Rapture was installed and my Dad, son and I went for a boat ride. It is about 3PM central time at MSL, 91 degree's. It is overcast with 54% humidity.
The top speed with the Rapture was 45.6 @ 5100 RPM's. At that speed/RPM the 115 Johnson was burning 13.0 to 13.1 GPH using the Northstar F210 meter.
Something noted with the Rapture was it's ability to hold without ventilation. You could trim this prop anywhere and it held. Turning was absolutely not a problem.
We had to slow way down due to rough water and found the prop did well at 10 MPH at 2000 RPM busting through the waves. The 115 V-4 is fantastic holding slow speeds compared to the Johnson 70 that was on the boat before. None of the speeding up and slowing down issues. At this slow 10 MPH speed we were getting a little better than 3 MPG, not too shabby! At all other speeds on plane the boat got in the 5 to 6 MPG range. This data is with a Garmin Hand held GPS and the Northstar F210 fuel monitor.
I do want to run the boat with a lighter load with this Rapture prop to see what RPM's and speed do. This 21 Rapture is for sure more prop than the old style 22 OMC Raker. The Raker is faster but the Rapture has way more manners for all around boating.
Now I am curious about the Stiletto Advantage
Comments welcome and needed.
Rick
ratherwhalering posted 09-17-2009 11:38 PM ET (US)
Rick, that sounds pretty darn good for a heavy load. If the RPMs go to 5400-5500 trimmed out with a light load, I think you have a winner. The Stiletto would be an interesting comparison, but I don't think it will give you any more top end speed. If you do decide to try a Stiletto, test it against the Rapture at increments of 500 RPM, and post you results.
I totally agree with your point that a propeller that operates well at all speeds is preferable to one that produces only top end performance. I love to go fast, but when I downloaded my E-TECs RPM data last spring, I was surprised at the results...I think my 5000-5500 RPM use was something like 3 percent of the use range.
Slick 50 posted 09-18-2009 12:30 AM ET (US)
Rob, thanks for the reply.
It is amazing the difference between props. Things you can not see make huge differences.
The Rapture appears to be the one at this point. I do want to see how it does with 2 people in the boat to see how it compares with the Raker 22 for speed. If that looks good I will do a performance test with the Rapture 21 at 500 RPM increments with speed and GPH fuel usage. The Northstar F210 has not been verified for accuracy but the WOT usage is close to what I would expect if not a little high.
The way the Rapture is biting with no ventilation, I wonder if the engine could be raised???
Rick
Teak Oil posted 09-22-2009 10:53 PM ET (US)
Slick 50 I run an older style 20" Raker on my 90hp V4 with good results, with a top speed of over 47 at 5300 rpms with only myself in the boat, and 45-46 with one passenger.
I use a 6" Rite Hite jackplate that I love. I can run the prop high most of the time with almost no venting issues, I only lower the engine for tubing. I have had some venting issues while tubing due to the tight turns I often make.
The nice thing about the Rite Hite is that it is adjustable on the fly, you just need to take a ratchet and two sockets and you can adjust and run, adjust and run, etc. I added a solid 3mph with the jackplate and bigger prop I could turn with it. You would see a gain in speed going to 6 inches of setback for sure, but since your motor is heavier than mine your Montauk may sit a little lower in the water than it does now.
You will surely top 50mph with the Rite Hite and the props you have now, but they are not cheap at a little over $300. They are a VERY high quality piece of equipment however
Slick 50 posted 09-23-2009 03:45 PM ET (US)
Teakoil, that is great speed with very little prop slip. I have a CMC hydraulic jack plate I could install but am wanting to see how everything works out without it first using the 2.5 inch set back. I believe your 90 weighs in at 300 lbs and the 2003 115 Johnson weighs in at 330 pounds. The lower unit gearing is 2:1 as I believe yours is.
Today I went for a run by myself with about 12 gallons of fuel, no other equipment other than safety stuff and the anchor. I was able to get 50.6 MPH running 2 directions averaged with the Michigan Wheel 21 Rapture. The 115 was burning 12.3 GPH at 5400 RPMs. I plan to do some 500 RPM increment testing soon for everyone to see. While running around I consistently got 5 to 6 MPG. I am thinking that is pretty good, any comments on that? As far as speed to RPMs go, the speed runs about 2 MPH behind the tach when properly trimmed for speed.
Yes, I am having fun.
Rick
Teak Oil posted 09-24-2009 07:35 PM ET (US)
I have averaged over 5mpg with my old 90 cruising at around 30 mph on several trips, so you are right in line with your economy.
Sounds like you are running really good, if you could get more setback and raise the motor you have plenty of rpms left as I believe your motor can run up to 6000rpms.
One thing I would do is take the boat out in some good 3' chop to make sure you have no venting issues in rough water. It would suck to get caught in some rough stuff and have your prop coming out of the water all the time with 20 miles to go.
I have had mine in 4-5 footers with no [unclear]. After that you [cannot] run on plane anyways so your motor height [does not] matter.
jimh posted 09-24-2009 08:16 PM ET (US)
I am not sure what is being said about the ability of a Boston Whaler boat to make way against five-foot high waves. My experience, in much larger boats, including 30-foot displacement hull boats that weighed 11,000-lbs and whose hull form had a very find and narrow entry, is that it is extraordinarily difficult to make headway against five-foot high waves.
The notion that a Boston Whaler MONTAUK 17 can make headway against five-foot head seas is remarkable. I have never tried to make headway against five-foot high head seas in a MONTAUK, but I really have no desire to try it. I cannot imagine it could be done in anything but rather extreme discomfort.
ratherwhalering posted 09-25-2009 01:54 AM ET (US)
Think frequency, Jim, frequency ;-)
Slick 50 posted 09-25-2009 08:11 AM ET (US)
Rob,
This Rapture 21 prop did exactly what you expected, 5400 RPMs. I believe it could be raised to get better top end but may loose all around performance. The 500 RPM increment test will get done soon, I have been pretty busy with other things.
Teakoil, this engine is rated 115 HP @ 5000 RPM and an operating range of 4500 to 5500 RPMs. The 5400 RPMs with a light load I am getting is just about perfect. At the engine height it is at now it handles rough water great. The earlier tests with the 22 OMC Raker surprised me compared to this Rapture prop. The Raker ventilated easily at this same engine height and would not allow as much trim change as the Rapture. I believe this is why the Raker was faster than the Rapture. The Raker was at it's max operating height and the prop was at the perfect angle for propulsion. If I were to raise the Rapture 21 to it's max height it would be faster but have less manners for all around performance. The advantage of hydraulic jack plates. Does this make sense or am I off base?
The comments about wave heights brings up a question. My understanding of wave heights relates to median. An example of 5 foot seas would have 10 foot high waves from the crest of the wave to the bottom of the trough, very rough if wave timing is short. What is everyone else's opinion on this or should this be another thread?
Rick
Tohsgib posted 09-25-2009 11:56 AM ET (US)
A 5 foot wave is a five foot tall wave, crest to trough. When they say a tidal wave was 30 feet high, they dd not mean 60.
ratherwhalering posted 09-25-2009 12:04 PM ET (US)
Rick, at 3-inches above the lowest keel point, you are going to have to start thinking about water pressure if you raise your engine any further. You want to avoid airated water in the cooling system at high RPM and speed, thus reducing the cooling capabilities of the engine and potentially increasing the engine temp for an extended period of time. Your lower end's water pick-up is quite low, however, and you could probably get away with it. I have a 1987 Montauk, 2004 E-TEC 90, 4-inch CMC set-back brackets, anti-ventilation plate 2 7/8 inches above LKP, Stiletto 13.25 x 15 Advantage I SS propeller, and I have super solid grip. I also believe we have the same lower unit. If I raise it up 1/2 inch, performance suffers and ventilation increases drastically. Water pressure, according to my pressure gauge, is still excellent.
(side note: I think your max RPMs are 5500 for that engine if it's a carbed 2-stroke.)
What the hell, give it a try! If you are doing 51.5 MPH at 5500 RPM, have no low and mid-range ventilation, and excellent water pressure, then keep it there. Every propeller is different.
Tohsgib posted 09-25-2009 12:23 PM ET (US)
My engine is up 4.5" and water presure is fine.
Teak Oil posted 09-25-2009 09:32 PM ET (US)
Jim there were mostly four footers and a few five footers on the way back from Beaver Island during the BW owners event in Charlevoix a few years ago. The only way I could stay on plane was to follow the 24' Outrage the president of BW was in and stay in his wake. I was also working the throttle like and offshore racer.
Other than a little spray and some tired legs we made it through the 30 mile trip back no worse for wear, and my prop never ventilated in spite of its high setting. This is what I was referring to in my earlier post which you thought required your unique style of editing.
And yes a five foot wave is five feet tall from the trough to the crest.
weekendwarrior posted 09-27-2009 08:25 AM ET (US)
I believe a 2' wave is indeed 4' from peak to trough. Just like when you graph any other type of wave. For example voltage. 2v a/c is 4v peak to trough. When the forecast is 2'-plus, I keep my Montauk in shore. :)
Tom W Clark posted 09-27-2009 08:31 AM ET (US)
Jesus, another thread arguing what wave height it is? It is not a difficult concept to understand. The vertical height from trough to crest. Thus a two foot wave is two feet from trough to crest, not four.
Slick 50 posted 09-27-2009 10:24 AM ET (US)
Many years ago I argued with a guy about wave height definition. I thought it was from trough to crest as anyone would think. This guy made me believe the way mentioned above and that is how I have thought for many years. A couple days ago I decided to look it up on the inter-net and all I could find was the simple trough to crest description. So, I was wrong all these years. It is much simpler this way!!
I have not been able to get the Montauk out for the performance runs. Monday my dad was diagnosed with stage 4B pancreatic cancer and things have been pretty hectic. He is tougher than the family about this.
I am excited about getting the data with the 115 Johnson on the Montauk. It will come.
Rick
weekendwarrior posted 09-27-2009 07:48 PM ET (US)
I was wrong on this one. NOAA (the group that reports the wave heights) defines "significant wave height" as:
"SIGNIFICANT WAVE HEIGHT is the average height in feet (from trough to crest) of the one-third highest waves for the indicated 12-hour period. The 12-hour periods begin and end at 0000 and 1200 UTC"
http://www.nws.noaa.gov/ndfd/definitions.htm
Note that this is not always the case. Some examples are listed here:
http://en.wikipedia.org/wiki/Wave_height

Tollyfamily posted 09-28-2009 05:29 PM ET (US)
I fished yesterday in Seattle with winds at 15-20 with 3' waves out of the north in my Montauk, while trolling at 2.5 mph for Coho the bow would bury to the rub rail at every wave. On the way back to the launch ramp heading mainly into the waves I could only run 10-11 mph or we would launch off the top and crash into the trough.
Dan

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Author	Topic: 1985 Montauk 17 and Johnson 115
Slick 50	posted 09-10-2009 06:45 PM ET (US) Yesterday my 22 pitch OMC Raker came in so it was time to take the [1985 Boston Whaler MONTAUK 17 with 115-HP Johnson motor] out for a run. My son and I grabbed a few drinks and filled the boat up with fuel for a test spin. With a calculated 950 pounds for the Montauk and an additional 1050 pounds of engine, fuel, gear and people, that adds up to about 2000 pounds. My original thought was the 22 Raker would be too much prop but it turned out to be pretty close. I plan to run a 21 pitch Michigan Wheel Raptor and also a 20 pitch OMC Raker for comparison. The original run of the 2003 115 HP Johnson was with a 17 pitch OMC SST propeller, the engine would easily over rev. This 2003 115 Johnson is a 2 stroke Bombardier carburetor 105 cubic inch engine. The engine is mounted on a 2.5 inch setback with the anti-ventilation plate about 3 to 3.5 inches above the keel of the boat. During the initial out-ting the SST did not blow out in turns but during the second out-ting the Raker would. I thought that was very strange. This Raker is the first edition Raker, not the series 2. I would consider dropping the engine one hole if this prop turns out to be the best choice??? The first WOT run turned out a 49.7 MPH at 5300 RPMs. The second run turned out a 48.9 MPH at 5200 RPMs. The third run turned out a 49.5 at 5300 RPMs. From this information, is there a better prop choice or engine mounting set up? I have a 5.5 inch CMC hydraulic jack plate I could put on but didn't due to weight. The hub kit for the Raptor should be here any day so I can test it. The 20 inch Raker will be here tomorrow. I feel the Montauk will break 50 MPH with just me in the boat along with less fuel, the 27 gallon tank was full. Any help and ideas would be great. Rick
ratherwhalering	posted 09-12-2009 02:14 PM ET (US) Rick, with the engine height and the problem with venting, I think you could try the Stiletto 13.25 x 19 Advantage I. Those Stilettos really like to run at higher settings, resist ventilation, and allow less drag from the lower unit as a result. My experience with these props makes me think it will run more like a fictional 21-inch Raker prop, and better than the Raptor 21, thus allowing higher RPM and better mid-range performance. Furthermore I think the 20-inch Raker (assuming it is not the 2-series) will have the same venting problems but allow you more RPM, however I doubt your top end speed will increase. I am interested in your thoughts and results. --Rob--
Slick 50	posted 09-12-2009 09:52 PM ET (US) Hi Rob, Thanks for your help. The Stiletto sounds like a good one. I will keep my eyes open for one. The ability for it to run shallow sounds like the ticket. With the engine turning the Raker 22 to 5300 RPMs with a average load, do you think the 19 Stiletto will do the job? I like your thinking about running a 19 for great bottom end and mid range. The 20 inch Raker came in today but was unable to run the boat due to water getting into the lower unit. This is a used unit that was just put on a couple weeks ago. I did change the oil on it when it was installed but after 2 runs it was found to have water in the oil. Today the new seals were installed and the lower unit is back on the engine. Tomorrow if the weather will clear up I can take the boat out again. The hub kit for the 21 Raptor is in the mail. The 49 MPH runs with the 22 Raker were in rainy weather, 92 degrees and at MSL. The speed was registered on a hand held Garmin GPS. Speeds were noted going against the tide and with the tide.
ratherwhalering	posted 09-12-2009 11:36 PM ET (US) Rick, I think the Raptor-21 will be pretty darn similar to the Stiletto 13.25 x 19 with regard to performance. Both have aggressive cupping and rake. Let's see the performance results. If the Raptor is running at 5400 RPM (my pencil estimate) and doesn't vent, I think you have found your prop. If it runs low RPM or vents, then maybe try the Stiletto. Before running out and buying a Stiletto, lets wait for Clark to chime in, he's really got a better understanding of the variety of props available and individual characteristics than I do.
ratherwhalering	posted 09-12-2009 11:40 PM ET (US) I know I just contradicted my earlier post, and I actually think the Stiletto would be a slightly better prop, but in retrospect I don't think the difference between the Stiletto 19 and Raptor 21 will be significant enough to justify the expense unless there is a poor performance report from the Raptor, which I don't really expect.
Slick 50	posted 09-13-2009 01:10 AM ET (US) Rob, this is all good. When I receive the hub for the 21 Raptor I will run the boat and report the results. Your experience is a great help. Thanks Rick
Tom W Clark	posted 09-14-2009 12:59 PM ET (US) I've never heard of a propeller model called Raptor. Perhaps you mean a Michigan Wheel Rapture? I have never but an Advantage against a Rapture in a same-boat/motor test so I'm not sure how it will play out. One nice thing about the newer Rapture props is they also use the square bore hub kits like Mercury, Stiletto, Turbo and some PowerTech models. Once you own the hub kit for your motor you can try many of those other propellers as well.
Slick 50	posted 09-14-2009 10:54 PM ET (US) Tom, you are correct about the Michigan Wheel prop. I guess I should look at it a little closer. Do you have an opinion why the Raker ventilated easier than the old style SST? The hub kit should be here later this week and the Montauk will be taken out for another test run. As mentioned, maybe a Stiletto Advantage will be next? I had bought a Northstar F210 fuel meter late last year but it quit working after this first use. I have been in contact with Navico Technical Support (Northstar) about replacing the faulty sender, no luck. I bought another sender this week and hopefully we will have fuel flow indication. Rick
Slick 50	posted 09-16-2009 06:58 PM ET (US) Little update on the 1985 Montauk/2003 Johnson 115. The hub kit for the Michigan Wheel Rapture came in today. The 21 Rapture was installed and my Dad, son and I went for a boat ride. It is about 3PM central time at MSL, 91 degree's. It is overcast with 54% humidity. The top speed with the Rapture was 45.6 @ 5100 RPM's. At that speed/RPM the 115 Johnson was burning 13.0 to 13.1 GPH using the Northstar F210 meter. Something noted with the Rapture was it's ability to hold without ventilation. You could trim this prop anywhere and it held. Turning was absolutely not a problem. We had to slow way down due to rough water and found the prop did well at 10 MPH at 2000 RPM busting through the waves. The 115 V-4 is fantastic holding slow speeds compared to the Johnson 70 that was on the boat before. None of the speeding up and slowing down issues. At this slow 10 MPH speed we were getting a little better than 3 MPG, not too shabby! At all other speeds on plane the boat got in the 5 to 6 MPG range. This data is with a Garmin Hand held GPS and the Northstar F210 fuel monitor. I do want to run the boat with a lighter load with this Rapture prop to see what RPM's and speed do. This 21 Rapture is for sure more prop than the old style 22 OMC Raker. The Raker is faster but the Rapture has way more manners for all around boating. Now I am curious about the Stiletto Advantage Comments welcome and needed. Rick
ratherwhalering	posted 09-17-2009 11:38 PM ET (US) Rick, that sounds pretty darn good for a heavy load. If the RPMs go to 5400-5500 trimmed out with a light load, I think you have a winner. The Stiletto would be an interesting comparison, but I don't think it will give you any more top end speed. If you do decide to try a Stiletto, test it against the Rapture at increments of 500 RPM, and post you results. I totally agree with your point that a propeller that operates well at all speeds is preferable to one that produces only top end performance. I love to go fast, but when I downloaded my E-TECs RPM data last spring, I was surprised at the results...I think my 5000-5500 RPM use was something like 3 percent of the use range.
Slick 50	posted 09-18-2009 12:30 AM ET (US) Rob, thanks for the reply. It is amazing the difference between props. Things you can not see make huge differences. The Rapture appears to be the one at this point. I do want to see how it does with 2 people in the boat to see how it compares with the Raker 22 for speed. If that looks good I will do a performance test with the Rapture 21 at 500 RPM increments with speed and GPH fuel usage. The Northstar F210 has not been verified for accuracy but the WOT usage is close to what I would expect if not a little high. The way the Rapture is biting with no ventilation, I wonder if the engine could be raised??? Rick
Teak Oil	posted 09-22-2009 10:53 PM ET (US) Slick 50 I run an older style 20" Raker on my 90hp V4 with good results, with a top speed of over 47 at 5300 rpms with only myself in the boat, and 45-46 with one passenger. I use a 6" Rite Hite jackplate that I love. I can run the prop high most of the time with almost no venting issues, I only lower the engine for tubing. I have had some venting issues while tubing due to the tight turns I often make. The nice thing about the Rite Hite is that it is adjustable on the fly, you just need to take a ratchet and two sockets and you can adjust and run, adjust and run, etc. I added a solid 3mph with the jackplate and bigger prop I could turn with it. You would see a gain in speed going to 6 inches of setback for sure, but since your motor is heavier than mine your Montauk may sit a little lower in the water than it does now. You will surely top 50mph with the Rite Hite and the props you have now, but they are not cheap at a little over $300. They are a VERY high quality piece of equipment however
Slick 50	posted 09-23-2009 03:45 PM ET (US) Teakoil, that is great speed with very little prop slip. I have a CMC hydraulic jack plate I could install but am wanting to see how everything works out without it first using the 2.5 inch set back. I believe your 90 weighs in at 300 lbs and the 2003 115 Johnson weighs in at 330 pounds. The lower unit gearing is 2:1 as I believe yours is. Today I went for a run by myself with about 12 gallons of fuel, no other equipment other than safety stuff and the anchor. I was able to get 50.6 MPH running 2 directions averaged with the Michigan Wheel 21 Rapture. The 115 was burning 12.3 GPH at 5400 RPMs. I plan to do some 500 RPM increment testing soon for everyone to see. While running around I consistently got 5 to 6 MPG. I am thinking that is pretty good, any comments on that? As far as speed to RPMs go, the speed runs about 2 MPH behind the tach when properly trimmed for speed. Yes, I am having fun. Rick
Teak Oil	posted 09-24-2009 07:35 PM ET (US) I have averaged over 5mpg with my old 90 cruising at around 30 mph on several trips, so you are right in line with your economy. Sounds like you are running really good, if you could get more setback and raise the motor you have plenty of rpms left as I believe your motor can run up to 6000rpms. One thing I would do is take the boat out in some good 3' chop to make sure you have no venting issues in rough water. It would suck to get caught in some rough stuff and have your prop coming out of the water all the time with 20 miles to go. I have had mine in 4-5 footers with no [unclear]. After that you [cannot] run on plane anyways so your motor height [does not] matter.
jimh	posted 09-24-2009 08:16 PM ET (US) I am not sure what is being said about the ability of a Boston Whaler boat to make way against five-foot high waves. My experience, in much larger boats, including 30-foot displacement hull boats that weighed 11,000-lbs and whose hull form had a very find and narrow entry, is that it is extraordinarily difficult to make headway against five-foot high waves. The notion that a Boston Whaler MONTAUK 17 can make headway against five-foot head seas is remarkable. I have never tried to make headway against five-foot high head seas in a MONTAUK, but I really have no desire to try it. I cannot imagine it could be done in anything but rather extreme discomfort.
ratherwhalering	posted 09-25-2009 01:54 AM ET (US) Think frequency, Jim, frequency ;-)
Slick 50	posted 09-25-2009 08:11 AM ET (US) Rob, This Rapture 21 prop did exactly what you expected, 5400 RPMs. I believe it could be raised to get better top end but may loose all around performance. The 500 RPM increment test will get done soon, I have been pretty busy with other things. Teakoil, this engine is rated 115 HP @ 5000 RPM and an operating range of 4500 to 5500 RPMs. The 5400 RPMs with a light load I am getting is just about perfect. At the engine height it is at now it handles rough water great. The earlier tests with the 22 OMC Raker surprised me compared to this Rapture prop. The Raker ventilated easily at this same engine height and would not allow as much trim change as the Rapture. I believe this is why the Raker was faster than the Rapture. The Raker was at it's max operating height and the prop was at the perfect angle for propulsion. If I were to raise the Rapture 21 to it's max height it would be faster but have less manners for all around performance. The advantage of hydraulic jack plates. Does this make sense or am I off base? The comments about wave heights brings up a question. My understanding of wave heights relates to median. An example of 5 foot seas would have 10 foot high waves from the crest of the wave to the bottom of the trough, very rough if wave timing is short. What is everyone else's opinion on this or should this be another thread? Rick
Tohsgib	posted 09-25-2009 11:56 AM ET (US) A 5 foot wave is a five foot tall wave, crest to trough. When they say a tidal wave was 30 feet high, they dd not mean 60.
ratherwhalering	posted 09-25-2009 12:04 PM ET (US) Rick, at 3-inches above the lowest keel point, you are going to have to start thinking about water pressure if you raise your engine any further. You want to avoid airated water in the cooling system at high RPM and speed, thus reducing the cooling capabilities of the engine and potentially increasing the engine temp for an extended period of time. Your lower end's water pick-up is quite low, however, and you could probably get away with it. I have a 1987 Montauk, 2004 E-TEC 90, 4-inch CMC set-back brackets, anti-ventilation plate 2 7/8 inches above LKP, Stiletto 13.25 x 15 Advantage I SS propeller, and I have super solid grip. I also believe we have the same lower unit. If I raise it up 1/2 inch, performance suffers and ventilation increases drastically. Water pressure, according to my pressure gauge, is still excellent. (side note: I think your max RPMs are 5500 for that engine if it's a carbed 2-stroke.) What the hell, give it a try! If you are doing 51.5 MPH at 5500 RPM, have no low and mid-range ventilation, and excellent water pressure, then keep it there. Every propeller is different.
Tohsgib	posted 09-25-2009 12:23 PM ET (US) My engine is up 4.5" and water presure is fine.
Teak Oil	posted 09-25-2009 09:32 PM ET (US) Jim there were mostly four footers and a few five footers on the way back from Beaver Island during the BW owners event in Charlevoix a few years ago. The only way I could stay on plane was to follow the 24' Outrage the president of BW was in and stay in his wake. I was also working the throttle like and offshore racer. Other than a little spray and some tired legs we made it through the 30 mile trip back no worse for wear, and my prop never ventilated in spite of its high setting. This is what I was referring to in my earlier post which you thought required your unique style of editing. And yes a five foot wave is five feet tall from the trough to the crest.
weekendwarrior	posted 09-27-2009 08:25 AM ET (US) I believe a 2' wave is indeed 4' from peak to trough. Just like when you graph any other type of wave. For example voltage. 2v a/c is 4v peak to trough. When the forecast is 2'-plus, I keep my Montauk in shore. :)
Tom W Clark	posted 09-27-2009 08:31 AM ET (US) Jesus, another thread arguing what wave height it is? It is not a difficult concept to understand. The vertical height from trough to crest. Thus a two foot wave is two feet from trough to crest, not four.
Slick 50	posted 09-27-2009 10:24 AM ET (US) Many years ago I argued with a guy about wave height definition. I thought it was from trough to crest as anyone would think. This guy made me believe the way mentioned above and that is how I have thought for many years. A couple days ago I decided to look it up on the inter-net and all I could find was the simple trough to crest description. So, I was wrong all these years. It is much simpler this way!! I have not been able to get the Montauk out for the performance runs. Monday my dad was diagnosed with stage 4B pancreatic cancer and things have been pretty hectic. He is tougher than the family about this. I am excited about getting the data with the 115 Johnson on the Montauk. It will come. Rick
weekendwarrior	posted 09-27-2009 07:48 PM ET (US) I was wrong on this one. NOAA (the group that reports the wave heights) defines "significant wave height" as: "SIGNIFICANT WAVE HEIGHT is the average height in feet (from trough to crest) of the one-third highest waves for the indicated 12-hour period. The 12-hour periods begin and end at 0000 and 1200 UTC" http://www.nws.noaa.gov/ndfd/definitions.htm Note that this is not always the case. Some examples are listed here: http://en.wikipedia.org/wiki/Wave_height
Tollyfamily	posted 09-28-2009 05:29 PM ET (US) I fished yesterday in Seattle with winds at 15-20 with 3' waves out of the north in my Montauk, while trolling at 2.5 mph for Coho the bow would bury to the rub rail at every wave. On the way back to the launch ramp heading mainly into the waves I could only run 10-11 mph or we would launch off the top and crash into the trough. Dan