MONTAUK 17: Affect of Jackplate on Performance

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Author Topic:   MONTAUK 17: Affect of Jackplate on Performance

Rockrock posted 02-15-2008 11:11 AM ET (US)
[How has installlation of a jackplate on a MONTAUK 17 affected the boat's performance?] The local dealer here advises against [installation of a jackplate on a Boston Whaler MONTAUK 17] for performance reasons.
Tohsgib posted 02-15-2008 02:53 PM ET (US)
Many here have [installed a jackplate on a Boston Whaler MONTAUK 17.] It is best $150 you can spend. I picked up a couple MPH but lost about 4" of draft--can't beat that. I had a 6" setback Vance with a 5" lift. Only downfall is water will come over the transom into splashwell if you are agressive in reverse.
NJCoastFlyFish posted 02-15-2008 04:01 PM ET (US)
Funny thing my dealer also advised against it. They said I would have to be running a more powerful setup built for speed and my little whaler would see no benefits.
Everyone on here that has done it has said mph and gph benefits so it definitely is something that would help, dealers can't know everything there is to know about every set up. I might do it next year when I have the cash lying around. You have to remember that on top of the jackplate you might also be looking at a longer steering cable, and a new prop.
I really don't care about the MPH increase or even the slight fuel economy benefits, but lowering my draft would be a godsend in some of the shallow areas I like to go clamming!
dscew posted 02-15-2008 04:43 PM ET (US)
I put a 4 inch setback jackplate on my 17 Katama (non-smirked hull) when I repowered last year. I think it's a great set-up. I needed longer control cables (needed new ones anyway with the new engine) but not a longer steering cable. Tohsgib is right, the cost came in right about $150.
Rockrock posted 02-16-2008 08:07 PM ET (US)
Thanks guys. I really need to reduce my draft in the Louisiana marsh. I hope the Jack Plate will fit the same holes in the trans. Also, can anyone suggest a model? I am mostly interested in a manual version I think?
dscew posted 02-16-2008 09:11 PM ET (US)
I used a CMC part number 40012 manual 2 piece setback jackplate from MageMarine.com. Setback is 4 inches, and it has 5 inches of vertical adjustment. It was $138 plus about $15.00 shipping. My hull is non-smirked, so I had to drill the new plate to line up with the non-standard holes in the transom. Not sure what the smirked hull transoms are like regarding the mounting holes. If anyone would know, I think it would be Tohsgib. CMC is very nice stuff, beefy and well made.
contender posted 02-16-2008 09:28 PM ET (US)
I like the idea of jakeplate,(I do not have one but have thought about purchasing one) and according to everyone on this site they do to. Better speed, MPG, etc. My question is since the engine is set back off the transom how much more tork is now applied to the transom?(Physics anyone) Since the boat is not design for this does it void your warranty? Or does the whaler factory recommend/condone one and if so why do they not make their own?
dscew posted 02-16-2008 11:17 PM ET (US)
There's a great deal of information in an article on brackets in the Reference section of this forum. It should tell you much of what you need to know. Also, there are photos of bracket installations there and in Cetacea. Good reading.
jimh posted 02-18-2008 10:26 AM ET (US)
I am afraid I do not clearly understand the dealer's advice against installation of a jack plate on a Boston Whaler 17 MONTUAK "for performance reasons."
What exactly do you mean? Did the dealer advise that installing a jack plate will cause the boat to go slower? To get worse fuel economy? To be more difficult to handle?

NJCoastFlyFish posted 02-18-2008 12:36 PM ET (US)
Jimh - My dealer told me it would be a waste of money and that a jack plate would have no affect on my boat at all. He said that due to the fact my boat is not built for speed and I only have 70hp on the back I wouldn't see any gains in performance. This is on a 1966 16ft hull. I figured if he was willing to shoot down a customer than he must be talking the truth because he only had money to gain from this but others on this site have said wonders about jackplates so I don't know!
sosmerc posted 02-19-2008 12:31 AM ET (US)
I would have to say that a jackplate on a Montauk with only 70hp is only going to provide a very marginal gain in performance. (it certainly won't hurt, other than the additional rigging clutter) If you are looking specifically for the ability to idle around in shallow water you probably want a hydraulic jack so that you can instantly adjust for your conditions. With a good stainless prop you will have the potential to gain a little more top speed by raising your engine, just be sure to monitor your water pressure so you don't hurt your engine.
I have had very good luck with the Bob's Machine hydraulic units. They have a variety of setbacks to choose from. They use the same industry standard hole pattern.
I guess this is on topic: I once had a 16 ft. flat bottom John Boat and I rigged it with a 1968 3 cylinder 55hp Evinrude short shaft. I added a transom jack AND hydraulic trim tabs. I ran the engine with a home-made tiller arm and used the standard side-mount push-button shift control.
The boat was a handful to say the least. I ran a nice OMC SST 19 pitch stainless at about 6000 rpm.
But the most fun was using the trim tabs and the jack to keep the boat "on plane" at a very slow cruise in only about a foot of water. I had some great fun with that little boat!! (the transom finally gave out from all the stress...I think it was rated for around 35hp max)
Tohsgib posted 02-19-2008 11:07 AM ET (US)
The main reason I used the jack plate was because my engine was mounted in the blind holes and it was easier to drill new holes in the plate then the transom. I will say that I have the best speed of anyone running a 70 on a 17' with 39.4 being my top. The main advantage was I ran it 4-5" above the keel which meant "I could" when running the flats instead of "I might not not make it".
Hydraulic plates are great but not on a 17'...too heavy and won't do much for you except in extreme conditions.
NJ..I understand where your mechanic is coming from. He is probably thinking about performance, not draft reduction which in my case is a performance enhancer. Just like some install nose cones which will not do ANYTHING unless you are running way over 60mph. They WILL however keep your engine running cool if you run high on a plate. Again no performance enhancements but the fact your engine does not overheat is definately a plus. Nosecones though do not like mud and easily clog, etc so I do not run one and do not run crazy elevation on my plate....though most who see it are puzzled on how high it is jacked up.
For the money, I do not not see why anyone would not run one...but that is me. I had a Vance on my 17', a CMC on my 13' and some other brand on my 19' and they all do the same thing and are built about the same quality, etc.
ratherwhalering posted 02-19-2008 05:40 PM ET (US)
I installed the CMC 4-inch set back brackets on my 1987 17-Montauk for the same reason Thoslglibbert (Nick) did, namely it was easier to drill a plate than a transom. The Montauk felt like a different boat afterward. Lighter, faster, easier to plane, and all around better performance. I was running a 1987 Johnson 90HP V-4 at the time, so you may not see such a dramatic change, but you will notice one. My engine is also about 4 inches higher now.

The non-standard mounting holes were not specific to any whaler model or year, actually it was a B.I.A. standard "blind hole" mount. Essentially, the lower mounting consisted of lag bolts run from inside the transon splashwell, through the transom, and into threaded holes in the engine bracket. Thus there were no nuts on the lower engine mounting bracket. The threaded holes on the engine bracket were closer together and higher up than the traditional through bolts, and therefore considered ideal for the Montauk's shallow splashwell...except there was (and is) no way to adjust engine height.
I sugguest if you are interested in raising the engine 3-4 inches you also install a quality stainless steel propeller such as a Stiletto. This will allow you to run the engine higher, with little or no ventilation in tight turns.
Rockrock posted 02-19-2008 05:51 PM ET (US)
Can anyone advise me further on the jack plate topic. My Montauk is a 1989 and my Yamaha is a 1989 90 ETF. My Yamaha manual recommends mounting the motor with the anti-cavitation plate between the bottom of the boat and 1 inch below. Using a straight edge along the bottom of the boat, and the motor tilted in the lowest position, it appears the anti-cavitation plate is between even with or possibly 1/2" above. I wonder if I can raise it any more with a jack plate and retain sufficient cooling? Reducing the draft is my objective. Thanks in advance for your advice.
deepwater posted 02-20-2008 04:15 PM ET (US)
Have you thought of a jet lower unit,,lots of river runner use them because of the rocks and they are shallow running
Casco Bay Outrage posted 02-20-2008 11:51 PM ET (US)
Rock -
Your current mounting is correct. For your model of Boston Whaler, the recommended mounting is for the anti-cavitiation plate to be above the bottom of the keel. It may need to go even higher. Other members can advise how much. Yamaha is providing a universal suggested height and is not considering your specific model of Boston Whaler or its hull design.
If you add a jack plate, the motor will need to go higher due to the setback from the transom.
If you do a search on "mounting height" and Montauk, you will see dozens of threads recommending this position.
CBO

Slippery Eel posted 02-21-2008 10:05 AM ET (US)
Ditto Ratherwhaling. Based on what I learned here I had the same set up installed. Altough I have not fully tweaked my set up as of yet the set up is great. As tohsgib noted you do have to be careful on a hard reverse unless you want to do a quick deck wash..
deepwater posted 02-21-2008 10:24 AM ET (US)
using a jack plate will only take you so far ,,like i said maybe you should look at a jet lower unit your draft should only be about 3 or 4 " below the keel
Tohsgib posted 02-21-2008 11:08 AM ET (US)
Jets are great but you need a 25" shaft I believe to mount on a 20" transom. They are also not good in mud or sand.

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Author	Topic: MONTAUK 17: Affect of Jackplate on Performance
Rockrock	posted 02-15-2008 11:11 AM ET (US) [How has installlation of a jackplate on a MONTAUK 17 affected the boat's performance?] The local dealer here advises against [installation of a jackplate on a Boston Whaler MONTAUK 17] for performance reasons.
Tohsgib	posted 02-15-2008 02:53 PM ET (US) Many here have [installed a jackplate on a Boston Whaler MONTAUK 17.] It is best $150 you can spend. I picked up a couple MPH but lost about 4" of draft--can't beat that. I had a 6" setback Vance with a 5" lift. Only downfall is water will come over the transom into splashwell if you are agressive in reverse.
NJCoastFlyFish	posted 02-15-2008 04:01 PM ET (US) Funny thing my dealer also advised against it. They said I would have to be running a more powerful setup built for speed and my little whaler would see no benefits. Everyone on here that has done it has said mph and gph benefits so it definitely is something that would help, dealers can't know everything there is to know about every set up. I might do it next year when I have the cash lying around. You have to remember that on top of the jackplate you might also be looking at a longer steering cable, and a new prop. I really don't care about the MPH increase or even the slight fuel economy benefits, but lowering my draft would be a godsend in some of the shallow areas I like to go clamming!
dscew	posted 02-15-2008 04:43 PM ET (US) I put a 4 inch setback jackplate on my 17 Katama (non-smirked hull) when I repowered last year. I think it's a great set-up. I needed longer control cables (needed new ones anyway with the new engine) but not a longer steering cable. Tohsgib is right, the cost came in right about $150.
Rockrock	posted 02-16-2008 08:07 PM ET (US) Thanks guys. I really need to reduce my draft in the Louisiana marsh. I hope the Jack Plate will fit the same holes in the trans. Also, can anyone suggest a model? I am mostly interested in a manual version I think?
dscew	posted 02-16-2008 09:11 PM ET (US) I used a CMC part number 40012 manual 2 piece setback jackplate from MageMarine.com. Setback is 4 inches, and it has 5 inches of vertical adjustment. It was $138 plus about $15.00 shipping. My hull is non-smirked, so I had to drill the new plate to line up with the non-standard holes in the transom. Not sure what the smirked hull transoms are like regarding the mounting holes. If anyone would know, I think it would be Tohsgib. CMC is very nice stuff, beefy and well made.
contender	posted 02-16-2008 09:28 PM ET (US) I like the idea of jakeplate,(I do not have one but have thought about purchasing one) and according to everyone on this site they do to. Better speed, MPG, etc. My question is since the engine is set back off the transom how much more tork is now applied to the transom?(Physics anyone) Since the boat is not design for this does it void your warranty? Or does the whaler factory recommend/condone one and if so why do they not make their own?
dscew	posted 02-16-2008 11:17 PM ET (US) There's a great deal of information in an article on brackets in the Reference section of this forum. It should tell you much of what you need to know. Also, there are photos of bracket installations there and in Cetacea. Good reading.
jimh	posted 02-18-2008 10:26 AM ET (US) I am afraid I do not clearly understand the dealer's advice against installation of a jack plate on a Boston Whaler 17 MONTUAK "for performance reasons." What exactly do you mean? Did the dealer advise that installing a jack plate will cause the boat to go slower? To get worse fuel economy? To be more difficult to handle?
NJCoastFlyFish	posted 02-18-2008 12:36 PM ET (US) Jimh - My dealer told me it would be a waste of money and that a jack plate would have no affect on my boat at all. He said that due to the fact my boat is not built for speed and I only have 70hp on the back I wouldn't see any gains in performance. This is on a 1966 16ft hull. I figured if he was willing to shoot down a customer than he must be talking the truth because he only had money to gain from this but others on this site have said wonders about jackplates so I don't know!
sosmerc	posted 02-19-2008 12:31 AM ET (US) I would have to say that a jackplate on a Montauk with only 70hp is only going to provide a very marginal gain in performance. (it certainly won't hurt, other than the additional rigging clutter) If you are looking specifically for the ability to idle around in shallow water you probably want a hydraulic jack so that you can instantly adjust for your conditions. With a good stainless prop you will have the potential to gain a little more top speed by raising your engine, just be sure to monitor your water pressure so you don't hurt your engine. I have had very good luck with the Bob's Machine hydraulic units. They have a variety of setbacks to choose from. They use the same industry standard hole pattern. I guess this is on topic: I once had a 16 ft. flat bottom John Boat and I rigged it with a 1968 3 cylinder 55hp Evinrude short shaft. I added a transom jack AND hydraulic trim tabs. I ran the engine with a home-made tiller arm and used the standard side-mount push-button shift control. The boat was a handful to say the least. I ran a nice OMC SST 19 pitch stainless at about 6000 rpm. But the most fun was using the trim tabs and the jack to keep the boat "on plane" at a very slow cruise in only about a foot of water. I had some great fun with that little boat!! (the transom finally gave out from all the stress...I think it was rated for around 35hp max)
Tohsgib	posted 02-19-2008 11:07 AM ET (US) The main reason I used the jack plate was because my engine was mounted in the blind holes and it was easier to drill new holes in the plate then the transom. I will say that I have the best speed of anyone running a 70 on a 17' with 39.4 being my top. The main advantage was I ran it 4-5" above the keel which meant "I could" when running the flats instead of "I might not not make it". Hydraulic plates are great but not on a 17'...too heavy and won't do much for you except in extreme conditions. NJ..I understand where your mechanic is coming from. He is probably thinking about performance, not draft reduction which in my case is a performance enhancer. Just like some install nose cones which will not do ANYTHING unless you are running way over 60mph. They WILL however keep your engine running cool if you run high on a plate. Again no performance enhancements but the fact your engine does not overheat is definately a plus. Nosecones though do not like mud and easily clog, etc so I do not run one and do not run crazy elevation on my plate....though most who see it are puzzled on how high it is jacked up. For the money, I do not not see why anyone would not run one...but that is me. I had a Vance on my 17', a CMC on my 13' and some other brand on my 19' and they all do the same thing and are built about the same quality, etc.
ratherwhalering	posted 02-19-2008 05:40 PM ET (US) I installed the CMC 4-inch set back brackets on my 1987 17-Montauk for the same reason Thoslglibbert (Nick) did, namely it was easier to drill a plate than a transom. The Montauk felt like a different boat afterward. Lighter, faster, easier to plane, and all around better performance. I was running a 1987 Johnson 90HP V-4 at the time, so you may not see such a dramatic change, but you will notice one. My engine is also about 4 inches higher now. The non-standard mounting holes were not specific to any whaler model or year, actually it was a B.I.A. standard "blind hole" mount. Essentially, the lower mounting consisted of lag bolts run from inside the transon splashwell, through the transom, and into threaded holes in the engine bracket. Thus there were no nuts on the lower engine mounting bracket. The threaded holes on the engine bracket were closer together and higher up than the traditional through bolts, and therefore considered ideal for the Montauk's shallow splashwell...except there was (and is) no way to adjust engine height. I sugguest if you are interested in raising the engine 3-4 inches you also install a quality stainless steel propeller such as a Stiletto. This will allow you to run the engine higher, with little or no ventilation in tight turns.
Rockrock	posted 02-19-2008 05:51 PM ET (US) Can anyone advise me further on the jack plate topic. My Montauk is a 1989 and my Yamaha is a 1989 90 ETF. My Yamaha manual recommends mounting the motor with the anti-cavitation plate between the bottom of the boat and 1 inch below. Using a straight edge along the bottom of the boat, and the motor tilted in the lowest position, it appears the anti-cavitation plate is between even with or possibly 1/2" above. I wonder if I can raise it any more with a jack plate and retain sufficient cooling? Reducing the draft is my objective. Thanks in advance for your advice.
deepwater	posted 02-20-2008 04:15 PM ET (US) Have you thought of a jet lower unit,,lots of river runner use them because of the rocks and they are shallow running
Casco Bay Outrage	posted 02-20-2008 11:51 PM ET (US) Rock - Your current mounting is correct. For your model of Boston Whaler, the recommended mounting is for the anti-cavitiation plate to be above the bottom of the keel. It may need to go even higher. Other members can advise how much. Yamaha is providing a universal suggested height and is not considering your specific model of Boston Whaler or its hull design. If you add a jack plate, the motor will need to go higher due to the setback from the transom. If you do a search on "mounting height" and Montauk, you will see dozens of threads recommending this position. CBO
Slippery Eel	posted 02-21-2008 10:05 AM ET (US) Ditto Ratherwhaling. Based on what I learned here I had the same set up installed. Altough I have not fully tweaked my set up as of yet the set up is great. As tohsgib noted you do have to be careful on a hard reverse unless you want to do a quick deck wash..
deepwater	posted 02-21-2008 10:24 AM ET (US) using a jack plate will only take you so far ,,like i said maybe you should look at a jet lower unit your draft should only be about 3 or 4 " below the keel
Tohsgib	posted 02-21-2008 11:08 AM ET (US) Jets are great but you need a 25" shaft I believe to mount on a 20" transom. They are also not good in mud or sand.