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Author Topic:   Going from 90 hp to 60 hp Merc to Yamaha

Naval Orange posted 03-06-2007 05:22 PM ET (US)
Something new. Circumstances require a 2004 Montauk 17 with a 90 hp Mercury "Smog Legal" CA engine having about 30 hrs of use, to undergo a "re-power" DOWN to a Yamaha 60 hp 4 stroke. This is unusual because most seek more power. Is the engine easily downsized? Or are other changes necessary? Like the steering? Suggestions and help would be most appreciated. Thanks.
Frozen Naval Orange
Buckda posted 03-06-2007 05:32 PM ET (US)
Naval -
The switch should be very easy, as the controls should be the same (or an inexpensive adapter on the ends of the cables may be necessary). The steering will be universal - so there's no problem there, and the guages should be ok, though I'd check with your local dealer to be sure. Some guages are "adjustable" with a setting switch on the back (i.e. the number of "poles" on a tachometer can be selected).
You're right - not many people downsize motors if the current motor is still running well, but in a recent repower survey that I did here, you'd be suprised at how many people have "downsized" the HP when converting to 4-stroke technology motors.
Best of luck,
Dave
Roswell posted 03-06-2007 06:04 PM ET (US)
I'm sure the weight of the 2 stroke 90 is about the same as a 60HP four stroke.
Teak Oil posted 03-06-2007 07:57 PM ET (US)
Why not get a Mercury 60 four stroke? It would make the switch as simple as possible.
Naval Orange posted 03-08-2007 01:13 PM ET (US)
I appreciate the effort and the answers. It was originally sold as a ski boat. I purchased it from the skier because during my ownership it will be used as a South Pacific fishing boat. Fuel is $12/gal. Geographically, Yamaha is the engine of choice down there and due to parts and repairs it makes a Yamaha repower mandatory. I am not an experienced boater but it makes no sense to reinvent the wheel when I can ask an experienced group like this. This is already more expensive than I had planned. There is a lot of Brand Loyalty out there. Central CA is not excatly a Boaters Paradise, most don't even recognize the BW Brand name. Boat owners here own "wake board boats" with powerful inboard engines. Everything is freshwater oriented. Yamaha Marine is a nonesixtent entity unless it is lake oriented. So I seek good answers where I can find them. My only purpose is to do it right the first time and to know enough about the names of the parts and pieces required to call them by their proper names. Another question I have read about in these forums is the use of a "Jack Plate". Is this another add on and is it something I should consider? Having written a Bible, I figure I should quit while I am ahead. Thank you.
Frozen Naval Orange
Buckda posted 03-09-2007 03:02 PM ET (US)
A Jack Plate is a combination performance and utility add-on. It generally slightly improves performance (see the reference section of this site for a great article on setback brackets) based on the "setback" and adds utility (shallow water running) with the ability to "jack" the engine to a higher position relative to the keel of the boat.
Neither a height adjustment nor a setback adjustment are necessary items on most Boston Whaler boats that are intended for general use unless you have an identified need.
This accessory is easily bolted onto the transom of most boats - if you think you may want one - consider buying your cables (steering, throttle and shift, battery, etc) with an additional foot or so so that you can easily "insert" a jackplate or setback bracket should you identify the need for this performance enhancement (boat a lot in shallow waters (i.e. flats fishing)).
If gasolineis $12 dollars per gallon where you are, you may want to spend the $300 or so on a jackplate, since having the prop run shallower may improve your fuel economy (how hard the motor needs to run to give you a specific speed), although it may take a few years to recoup the initial cost of a bracket/jackplate in fuel savings.
If fuel were that expensive here, I think my boating would be seriously curtailed, or I'd take up sailing on the side.
Best regards!
Dave
Buckda posted 03-09-2007 03:02 PM ET (US)
A Jack Plate is a combination performance and utility add-on. It generally slightly improves performance (see the reference section of this site for a great article on setback brackets) based on the "setback" and adds utility (shallow water running) with the ability to "jack" the engine to a higher position relative to the keel of the boat.
Neither a height adjustment nor a setback adjustment are necessary items on most Boston Whaler boats that are intended for general use unless you have an identified need.
This accessory is easily bolted onto the transom of most boats - if you think you may want one - consider buying your cables (steering, throttle and shift, battery, etc) with an additional foot or so so that you can easily "insert" a jackplate or setback bracket should you identify the need for this performance enhancement (boat a lot in shallow waters (i.e. flats fishing)).
If gasolineis $12 dollars per gallon where you are, you may want to spend the $300 or so on a jackplate, since having the prop run shallower may improve your fuel economy (how hard the motor needs to run to give you a specific speed), although it may take a few years to recoup the initial cost of a bracket/jackplate in fuel savings.
If fuel were that expensive here, I think my boating would be seriously curtailed, or I'd take up sailing on the side.
Best regards!
Dave

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Author	Topic: Going from 90 hp to 60 hp Merc to Yamaha
Naval Orange	posted 03-06-2007 05:22 PM ET (US) Something new. Circumstances require a 2004 Montauk 17 with a 90 hp Mercury "Smog Legal" CA engine having about 30 hrs of use, to undergo a "re-power" DOWN to a Yamaha 60 hp 4 stroke. This is unusual because most seek more power. Is the engine easily downsized? Or are other changes necessary? Like the steering? Suggestions and help would be most appreciated. Thanks. Frozen Naval Orange
Buckda	posted 03-06-2007 05:32 PM ET (US) Naval - The switch should be very easy, as the controls should be the same (or an inexpensive adapter on the ends of the cables may be necessary). The steering will be universal - so there's no problem there, and the guages should be ok, though I'd check with your local dealer to be sure. Some guages are "adjustable" with a setting switch on the back (i.e. the number of "poles" on a tachometer can be selected). You're right - not many people downsize motors if the current motor is still running well, but in a recent repower survey that I did here, you'd be suprised at how many people have "downsized" the HP when converting to 4-stroke technology motors. Best of luck, Dave
Roswell	posted 03-06-2007 06:04 PM ET (US) I'm sure the weight of the 2 stroke 90 is about the same as a 60HP four stroke.
Teak Oil	posted 03-06-2007 07:57 PM ET (US) Why not get a Mercury 60 four stroke? It would make the switch as simple as possible.
Naval Orange	posted 03-08-2007 01:13 PM ET (US) I appreciate the effort and the answers. It was originally sold as a ski boat. I purchased it from the skier because during my ownership it will be used as a South Pacific fishing boat. Fuel is $12/gal. Geographically, Yamaha is the engine of choice down there and due to parts and repairs it makes a Yamaha repower mandatory. I am not an experienced boater but it makes no sense to reinvent the wheel when I can ask an experienced group like this. This is already more expensive than I had planned. There is a lot of Brand Loyalty out there. Central CA is not excatly a Boaters Paradise, most don't even recognize the BW Brand name. Boat owners here own "wake board boats" with powerful inboard engines. Everything is freshwater oriented. Yamaha Marine is a nonesixtent entity unless it is lake oriented. So I seek good answers where I can find them. My only purpose is to do it right the first time and to know enough about the names of the parts and pieces required to call them by their proper names. Another question I have read about in these forums is the use of a "Jack Plate". Is this another add on and is it something I should consider? Having written a Bible, I figure I should quit while I am ahead. Thank you. Frozen Naval Orange
Buckda	posted 03-09-2007 03:02 PM ET (US) A Jack Plate is a combination performance and utility add-on. It generally slightly improves performance (see the reference section of this site for a great article on setback brackets) based on the "setback" and adds utility (shallow water running) with the ability to "jack" the engine to a higher position relative to the keel of the boat. Neither a height adjustment nor a setback adjustment are necessary items on most Boston Whaler boats that are intended for general use unless you have an identified need. This accessory is easily bolted onto the transom of most boats - if you think you may want one - consider buying your cables (steering, throttle and shift, battery, etc) with an additional foot or so so that you can easily "insert" a jackplate or setback bracket should you identify the need for this performance enhancement (boat a lot in shallow waters (i.e. flats fishing)). If gasolineis $12 dollars per gallon where you are, you may want to spend the $300 or so on a jackplate, since having the prop run shallower may improve your fuel economy (how hard the motor needs to run to give you a specific speed), although it may take a few years to recoup the initial cost of a bracket/jackplate in fuel savings. If fuel were that expensive here, I think my boating would be seriously curtailed, or I'd take up sailing on the side. Best regards! Dave
Buckda	posted 03-09-2007 03:02 PM ET (US) A Jack Plate is a combination performance and utility add-on. It generally slightly improves performance (see the reference section of this site for a great article on setback brackets) based on the "setback" and adds utility (shallow water running) with the ability to "jack" the engine to a higher position relative to the keel of the boat. Neither a height adjustment nor a setback adjustment are necessary items on most Boston Whaler boats that are intended for general use unless you have an identified need. This accessory is easily bolted onto the transom of most boats - if you think you may want one - consider buying your cables (steering, throttle and shift, battery, etc) with an additional foot or so so that you can easily "insert" a jackplate or setback bracket should you identify the need for this performance enhancement (boat a lot in shallow waters (i.e. flats fishing)). If gasolineis $12 dollars per gallon where you are, you may want to spend the $300 or so on a jackplate, since having the prop run shallower may improve your fuel economy (how hard the motor needs to run to give you a specific speed), although it may take a few years to recoup the initial cost of a bracket/jackplate in fuel savings. If fuel were that expensive here, I think my boating would be seriously curtailed, or I'd take up sailing on the side. Best regards! Dave