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Author Topic:   MONTAUK 17: Installing a Yamaha F70

Morgan posted 02-27-2012 12:31 PM ET (US)
I have been reading several threads on installing a new motor on a Classic Montauk 17 and I'm a little confused. Please [bear] with me, as I'm a first time boat and Whaler owner as of about two weeks ago and have no experience in this area.
I have heard several posts suggesting that the motor should be mounted two or three holes up and I have come to learn that this is in regards to holes in the motor bracket itself (I originally thought this was referring to holes in the boats transom). If you guys could help to clarify a few things for me, it would be greatly appreciated.
My boat is a 1979 Montauk 17 and had a 1979 Johnson 70 on it. My boat is currently at the shop where they will be installing a brand new Yamaha F70 on it. My biggest concern is that they will be drilling the transom (if needed) in the correct area. I was under the impression that they would be able to use the top two holes from where the Johnson is located and have to drill two lower holes using a template which is provided with the motor? They would then fill the lower holes where the Johnson was mounted before. Do I need to be worried about if they will be drilling in the incorrect area? Is there certain preset holes that should be drilled for a new motor? I've read about the issues with a shallow splashwell, but I'm not sure if that applies to my boat.
With regards to which holes to mount the motor on, I have seen suggestions on two or three holes up and that the anti cavitation plate should be 1 to 1.5 inches above the bottom of the boat. What are the advantages and disadvantages of mounting the motor higher? It seems the disadvantages of mounting the motor two low are porpoising, tougher steering, slower to jump on plane, nose two high when running. The advantages of mounting it higher are the exact opposite of what I just mentioned. Could the disadvantages be stress on the transom and making the boat more top heavy and prone to turtling? I'm in southern California and will be boating in the rough pacific. I'm wondering if mounting the motor higher, could become an issue in a following sea? I will have two batteries in the console and a 30 gallon bait tank directly behind the RPS.
My other question is on an aluminum vs stainless steel prop. I was planning on going with the OEM Yamaha Aluminum 13 1/2 Diameter, 15 pitch, 3 blade prop. The shop recommended aluminum over stainless steel for a few reasons. They said stainless steel props can end up causing more gear case damage overtime due to their weight. It takes more to start rotating them and stop rotating them. There is also the argument about hitting something with a stainless vs aluminum prop, which appears to be a huge debate. They said if I was constantly running long distances off shore at fast speeds and wanted peak performance, then stainless would be the way to go. But since I will be fishing inshore, making short runs a few miles here and there in rougher seas, where I can't run do fast. I might as well get aluminum as it could save me from having to do gearcase work in the long run. Does this seem logical to you?
If so, should I still mount the motor two or three holes up if I'm considering the above aluminum prop?
Please help me out as I want to make sure they are doing things correctly. Sorry for such a long post, I just want to make sure I had everything covered and I only have about one day to make sure everything gets done right.
bloller posted 02-27-2012 06:40 PM ET (US)
Mount the motor one hole or two holes up meaning use the second set or third set of holes in the upper engine bracket. Fill the lower holes if they do not line up with any holes in the lower portion of the bracket and drill two new holes making sure that they go through into the splashwell.
Aluminum vs. stainless is a personal preference. The performance improvement with stainless would be minimal maybe 1 or 2mph on the top speed. The best part about stainless props are there durability. A stainless prop would probably last the lifetime of the motor while you may go through many aluminum props.
bloller posted 02-27-2012 06:52 PM ET (US)
I would not raise the motor three holes up since you will be using it in the Pacific and prop could blow out(ventilate) in swells. Just make sure AV plate is at least level with the keel. I raised my motor up off the transom two holes. Did not notice significant changes in rpms or speed but it did greatly reduce steering torque.

I don't think premature gearcase failure can be contributed to the prop material and you will be fine with a aluminum prop as long as you dont go above about .5-1" above the keel
jimh posted 02-27-2012 08:47 PM ET (US)
To understand engine mounting to the transom, please read the FAQ on that topic:
http://continuouswave.com/whaler/reference/FAQ/#Q8
Wendell Fox posted 02-27-2012 09:47 PM ET (US)
I think your making a very serious and expensive mistake in re powering your boat with a Yamaha 70. I'm very familiar with the boat you have just purchased. Fished on it many times with the previous owner. Let me say politely that the plans you have for your boat (heavy bait tank, extra battery, moving the console forward, 3 200 pound fisherman) will render your boat under powered and un seaworthy. Many people on this board have recommend an ETEC 90. Why are you disregarding that advice? I'm speaking from experience having owned two 17 Montauks with over 30 years operating experience with them in SF Bay and offshore. Additionally you should seriously consider the requirement for new holes in your transom to mount the Yamaha. It's my understanding the ETEC's top bolt pattern will match existing holes already drilled for the old Johnson 70. If it was my boat I would seriously reconsider everything your planning for one of the most pristine classic whalers to be had anywhere.
Phil T posted 02-28-2012 08:41 AM ET (US)
Engine manufacturers of older motors did not always follow the BIA standard mounting hole pattern adopted by manufacturers in the late 80's
In most cases dealers mounted motors on whalers using the blind holes and using lags.
It is not recommended to mount a motor all the way down and using the blind holes.
boatinpete posted 02-28-2012 03:13 PM ET (US)
Morgan let us know how the F70 runs compared to the 70 smoker as I too am very interested in this engine for a re-power.
Morgan posted 02-28-2012 04:18 PM ET (US)
Bloller...Thanks for the advice on how to mount the motor. I appreaciate that you took into account where I will be boating. Overall consensus, seems to be to mount the motor two holes up. I assume this means the motor will not be resting on the transom and all the weight will be on the bolts. Why do you need to switch to stainless as you start to move the motor up?
Jim...Thanks for sharing the link, that is very helpful
boatinpete...I'll definitely share the specs of how the F70 runs once I get it installed.
L H G posted 02-29-2012 01:21 AM ET (US)
As I stated elsewhere, with a 1979 Montauk splashwell, you really don't have any other choice but to mount a modern BIA bolt hole pattern engine 2 holes up. It won't go any lower.
Tom W Clark posted 02-29-2012 10:05 AM ET (US)
Morgan -- Have your motor mounted as high as it can go, three holes up. There is no reason not to. As one person explained elsewhere:
"I mounted a brand new 70 Yamaha 4 stroke. At first the boat store mounted it one hole up, that means the second hole from the top. I ran it about 6 hours in two trips and it seemed fine. But then I was told by Tom Clark on this site I should mount it three holes up in other words mount top bolt in the fourth hole from the top. WoW what a difference. Easier steering, get's up on plane faster. I'm sure a few mph faster, don't have speedo."
The bolt hole spacing in the transom will not be the BIA standard but the horizontal spacing will match the BIA spacing but the lower holes in the transom will be only 6-1/2 inches below the top holes instead of 8 inches.
Yes, it is possible to mount a motor only one hole up on a 1979 Montauk with 7-1/4 inch vertical bolt spacing but you have to angle the lower bolts upwards to reach the splashwell. This is a terrible detail and since there is NO REASON ON EARTH why anybody would want an outboard mounted only one hole up on the transom of a classic 16'-7" Whaler, there is no reason to do so.
Your dealer is wrong about the use of stainless steel propellers; it will cause no harm at all to your new motor in the short or the long run. There is exactly one reason aluminum propellers still exist: that are a lot cheaper to buy initially. Beyond that, they offer exactly zero advantages over a stainless steel prop and because they are so much more durable, even the cost advantage goes away over time.
Tohsgib posted 03-01-2012 02:13 PM ET (US)
If the alum prop is NOT free, go with SS and never worry about it.
Tom W Clark posted 03-02-2012 06:58 PM ET (US)
Here is another data point:
A friend of mine repowered his 2002 classic Montauk this fall with a Yamaha F70. On my advice, he had the motor mounted at its highest mounting position, three holes up.
After trying the 13-1/4" x 16" Yamaha Performance Series three blade, it was determined that was too much pitch. A 13-1/4" x 14" Yamaha Performance Series three blade was substituted and it turned out to be perfect, 38 MPH at 6200 RPM with a two people and a normal load.
It should be noted that the 13-1/4" x 14" Yamaha Performance Series three blade is essentially the same propeller as a 13-1/4" x 13" Stiletto Advantage 4.25, both are made by Precision Propeller Industries, Inc. as is the 13-1/4" x 13" Turbo 1.

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Author	Topic: MONTAUK 17: Installing a Yamaha F70
Morgan	posted 02-27-2012 12:31 PM ET (US) I have been reading several threads on installing a new motor on a Classic Montauk 17 and I'm a little confused. Please [bear] with me, as I'm a first time boat and Whaler owner as of about two weeks ago and have no experience in this area. I have heard several posts suggesting that the motor should be mounted two or three holes up and I have come to learn that this is in regards to holes in the motor bracket itself (I originally thought this was referring to holes in the boats transom). If you guys could help to clarify a few things for me, it would be greatly appreciated. My boat is a 1979 Montauk 17 and had a 1979 Johnson 70 on it. My boat is currently at the shop where they will be installing a brand new Yamaha F70 on it. My biggest concern is that they will be drilling the transom (if needed) in the correct area. I was under the impression that they would be able to use the top two holes from where the Johnson is located and have to drill two lower holes using a template which is provided with the motor? They would then fill the lower holes where the Johnson was mounted before. Do I need to be worried about if they will be drilling in the incorrect area? Is there certain preset holes that should be drilled for a new motor? I've read about the issues with a shallow splashwell, but I'm not sure if that applies to my boat. With regards to which holes to mount the motor on, I have seen suggestions on two or three holes up and that the anti cavitation plate should be 1 to 1.5 inches above the bottom of the boat. What are the advantages and disadvantages of mounting the motor higher? It seems the disadvantages of mounting the motor two low are porpoising, tougher steering, slower to jump on plane, nose two high when running. The advantages of mounting it higher are the exact opposite of what I just mentioned. Could the disadvantages be stress on the transom and making the boat more top heavy and prone to turtling? I'm in southern California and will be boating in the rough pacific. I'm wondering if mounting the motor higher, could become an issue in a following sea? I will have two batteries in the console and a 30 gallon bait tank directly behind the RPS. My other question is on an aluminum vs stainless steel prop. I was planning on going with the OEM Yamaha Aluminum 13 1/2 Diameter, 15 pitch, 3 blade prop. The shop recommended aluminum over stainless steel for a few reasons. They said stainless steel props can end up causing more gear case damage overtime due to their weight. It takes more to start rotating them and stop rotating them. There is also the argument about hitting something with a stainless vs aluminum prop, which appears to be a huge debate. They said if I was constantly running long distances off shore at fast speeds and wanted peak performance, then stainless would be the way to go. But since I will be fishing inshore, making short runs a few miles here and there in rougher seas, where I can't run do fast. I might as well get aluminum as it could save me from having to do gearcase work in the long run. Does this seem logical to you? If so, should I still mount the motor two or three holes up if I'm considering the above aluminum prop? Please help me out as I want to make sure they are doing things correctly. Sorry for such a long post, I just want to make sure I had everything covered and I only have about one day to make sure everything gets done right.
bloller	posted 02-27-2012 06:40 PM ET (US) Mount the motor one hole or two holes up meaning use the second set or third set of holes in the upper engine bracket. Fill the lower holes if they do not line up with any holes in the lower portion of the bracket and drill two new holes making sure that they go through into the splashwell. Aluminum vs. stainless is a personal preference. The performance improvement with stainless would be minimal maybe 1 or 2mph on the top speed. The best part about stainless props are there durability. A stainless prop would probably last the lifetime of the motor while you may go through many aluminum props.
bloller	posted 02-27-2012 06:52 PM ET (US) I would not raise the motor three holes up since you will be using it in the Pacific and prop could blow out(ventilate) in swells. Just make sure AV plate is at least level with the keel. I raised my motor up off the transom two holes. Did not notice significant changes in rpms or speed but it did greatly reduce steering torque. I don't think premature gearcase failure can be contributed to the prop material and you will be fine with a aluminum prop as long as you dont go above about .5-1" above the keel
jimh	posted 02-27-2012 08:47 PM ET (US) To understand engine mounting to the transom, please read the FAQ on that topic: http://continuouswave.com/whaler/reference/FAQ/#Q8
Wendell Fox	posted 02-27-2012 09:47 PM ET (US) I think your making a very serious and expensive mistake in re powering your boat with a Yamaha 70. I'm very familiar with the boat you have just purchased. Fished on it many times with the previous owner. Let me say politely that the plans you have for your boat (heavy bait tank, extra battery, moving the console forward, 3 200 pound fisherman) will render your boat under powered and un seaworthy. Many people on this board have recommend an ETEC 90. Why are you disregarding that advice? I'm speaking from experience having owned two 17 Montauks with over 30 years operating experience with them in SF Bay and offshore. Additionally you should seriously consider the requirement for new holes in your transom to mount the Yamaha. It's my understanding the ETEC's top bolt pattern will match existing holes already drilled for the old Johnson 70. If it was my boat I would seriously reconsider everything your planning for one of the most pristine classic whalers to be had anywhere.
Phil T	posted 02-28-2012 08:41 AM ET (US) Engine manufacturers of older motors did not always follow the BIA standard mounting hole pattern adopted by manufacturers in the late 80's In most cases dealers mounted motors on whalers using the blind holes and using lags. It is not recommended to mount a motor all the way down and using the blind holes.
boatinpete	posted 02-28-2012 03:13 PM ET (US) Morgan let us know how the F70 runs compared to the 70 smoker as I too am very interested in this engine for a re-power.
Morgan	posted 02-28-2012 04:18 PM ET (US) Bloller...Thanks for the advice on how to mount the motor. I appreaciate that you took into account where I will be boating. Overall consensus, seems to be to mount the motor two holes up. I assume this means the motor will not be resting on the transom and all the weight will be on the bolts. Why do you need to switch to stainless as you start to move the motor up? Jim...Thanks for sharing the link, that is very helpful boatinpete...I'll definitely share the specs of how the F70 runs once I get it installed.
L H G	posted 02-29-2012 01:21 AM ET (US) As I stated elsewhere, with a 1979 Montauk splashwell, you really don't have any other choice but to mount a modern BIA bolt hole pattern engine 2 holes up. It won't go any lower.
Tom W Clark	posted 02-29-2012 10:05 AM ET (US) Morgan -- Have your motor mounted as high as it can go, three holes up. There is no reason not to. As one person explained elsewhere: "I mounted a brand new 70 Yamaha 4 stroke. At first the boat store mounted it one hole up, that means the second hole from the top. I ran it about 6 hours in two trips and it seemed fine. But then I was told by Tom Clark on this site I should mount it three holes up in other words mount top bolt in the fourth hole from the top. WoW what a difference. Easier steering, get's up on plane faster. I'm sure a few mph faster, don't have speedo." The bolt hole spacing in the transom will not be the BIA standard but the horizontal spacing will match the BIA spacing but the lower holes in the transom will be only 6-1/2 inches below the top holes instead of 8 inches. Yes, it is possible to mount a motor only one hole up on a 1979 Montauk with 7-1/4 inch vertical bolt spacing but you have to angle the lower bolts upwards to reach the splashwell. This is a terrible detail and since there is NO REASON ON EARTH why anybody would want an outboard mounted only one hole up on the transom of a classic 16'-7" Whaler, there is no reason to do so. Your dealer is wrong about the use of stainless steel propellers; it will cause no harm at all to your new motor in the short or the long run. There is exactly one reason aluminum propellers still exist: that are a lot cheaper to buy initially. Beyond that, they offer exactly zero advantages over a stainless steel prop and because they are so much more durable, even the cost advantage goes away over time.
Tohsgib	posted 03-01-2012 02:13 PM ET (US) If the alum prop is NOT free, go with SS and never worry about it.
Tom W Clark	posted 03-02-2012 06:58 PM ET (US) Here is another data point: A friend of mine repowered his 2002 classic Montauk this fall with a Yamaha F70. On my advice, he had the motor mounted at its highest mounting position, three holes up. After trying the 13-1/4" x 16" Yamaha Performance Series three blade, it was determined that was too much pitch. A 13-1/4" x 14" Yamaha Performance Series three blade was substituted and it turned out to be perfect, 38 MPH at 6200 RPM with a two people and a normal load. It should be noted that the 13-1/4" x 14" Yamaha Performance Series three blade is essentially the same propeller as a 13-1/4" x 13" Stiletto Advantage 4.25, both are made by Precision Propeller Industries, Inc. as is the 13-1/4" x 13" Turbo 1.