1987 Montauk Stock Seat Height for Fuel Tank

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Author Topic:   1987 Montauk Stock Seat Height for Fuel Tank

queenfish posted 12-07-2013 02:29 PM ET (US)
We own a 1987 Montauk that we keep down in Baja and it needs new fuel tanks.
We can't really measure them since it is a thousand miles away. Does anyone know the exact dimensions of the space under the stock seat? Has anyone else replaced their tanks with some of the stuff now available?
Please.
Thanks.
Mark

DVollrath posted 12-07-2013 03:18 PM ET (US)
Mark,
The Mirax D-1212 tank is made for a BW Montauk. It's measurements are 12(h) x 14(w) x 18.75(l). I don't believe this includes the fill neck & cap on the height, nor the handles on the length. These tank fit perfectly in the mats under the RPS. I have a pair on my 1988 Montauk. The fill assembly is perhaps 1.5" higher than the top of the tank body.
I can take exact measurements in a week or so, but the above numbers are reasonably accurate.
Dennis
The Chesapeake Explorer posted 12-07-2013 08:36 PM ET (US)
My 1987 Montauk is height from deck to bottom of seat 14 3/4" There is the hole in the deck for the fuel line with a oval trim ring around it. The oval trim ring is 1/4 inch high. This is right below the seat to the rear center. The red mats are 1/4 " thick where the tanks sit.
Width of both red gas tank mats 31.5 " This is the space between the seat supports on the port and starbord sides.This includes the space between the tanks
Lenght of red Gas tank mat 21.5 " This is how wide from the front of the boat to the rear the mats are. The seat is about 19 inches wide, the gas tank mats are longer then the width of the seat they stick to the rear about 2 inches and are lined up with the seat to the front.
The gas tank mats have a edge about 1/2 inch wide all around so 1" would be subtracted to fit within the gas tank mat front to rear. Useually when a large 24 gal tank is placed the edges of the mat are cut/trimmed so the tank will go in, or the mats are removed by drilling out the pop rivets that hold them, Mine are in rough shape as most will be with 26 years age.
Bottom line 14 3/4 high 31.5 wide 21.5 deep is the size of the area less a bit for clearence a 1/8 -1/4 inch
The mats are 21.5 X 14 wide total including the edge and will take a tank 12.5 wide and 19 long if you are using seperate tanks with 14 1/2 from the mat surface to the bottom of the seat for total tank filler or fuel line fitting height and 14 1/2 tall would be scraping the bottom of the seat.
Now the hole for the gas line in right under the seat on mine, This can differ as to where the dealer put it. Many of the big tanks will go over this hole, some have a divot in the tank so the hose can go in the original hole, others you may have to drill a new fuel line hole to the tunnel. I really wish tank makers could get this right.
The Chesapeake Explorer posted 12-07-2013 08:48 PM ET (US)
Some explaination between the sizes on tanks on the post above mine.
As I state the mat size for a tank is 12.5 X 19 . Now this would be if you had a rectangle tank that sat right into the mat with side that went stright up. The steel 12 gal Long Cruise tanks, which I had for 25 years were a bit wider then 12.5 inches but they are round on the edges side to side not square. They fit in the "footprint" of the 12.5 X 19 dimension as the radius of the tank comes over the sides of the mat edge. Other tanks with rounded edges may be simular. The 31.5 width is the max size for tanks side to side to the seat supports.
frontier posted 12-07-2013 10:41 PM ET (US)
Take a look at the Moeller #031626 fuel tank.
Specifically designed for use under the RPS in a Boston Whaler Montauk.
Rear slanted gas cap makes it easy to fill without moving the tank. Fuel hose floor opening works fine - I just cut the factory plastic surround piece so the tank lays flat.
No tank mats necessary.
We've used several over the years including in our current classic Montauk.
Works great.
The Chesapeake Explorer posted 12-08-2013 10:14 AM ET (US)
My 12 gal steel Long cruise tanks were great, they fit perfect and lasted a long time, finally they developed pin holes in the bottoms all though I painted them and glassed the bottoms. Last year the last one went to the dump. I wish they still were made. They were about 90 dollars each A bit less the cost today as the Mirax with inflation .
I have a couple of plastic tanks a 3 gal and a 6 I got both cheap on sales.The 3 is a extra tank that I grab if Im going any distance. I now use the 6 and a old Evinrude steel 6 gal tank that came with my original motor. Plus the 3 gal.
I have long thought of a big 24-27 gal tank I looked at the Pate some time ago, they developed troubles with ethanol gas. The Moller as described above is a nice tank I have considered that one and will have to place a new fuel hose hole in the deck if I ever go with that.
A couple of issues I have , had has me sitting it out with the plastic cheap tanks, One is that fuel does not keep very long and goes stale faster then in the past. I have gone out and had sour fuel stop me and changed tanks got back then had to drain out the bad gas and burn it off in my old truck little by little, a hassle. Gas stabilizer does work but its also not cheap.
The Mirax tanks are similure to my original Long Cruise, and are very nice looking, they are also expensive as they are high quality and custom made. They can be removed easy and drained of gas if the boats sitting a while.
This is a advantage to the Mirax tanks.
With the price of gas today , Montauk tanks are easy to steal hence with the Mirax tanks there goes gas plus expensive tanks and thats a disadvantage.
The Moller would be hard to steal as its big, but it can be done and with even 15 gallons in it, would be satisfying work for a thief. Of course its size makes it difficult to just pour out the gas into say a 5 gallon bucket then funnel into a thieves car. Perhaps a nice gas thief will simply siphon off the gas and leave the tank which would be Ok with me. When I get tired of my current tanks I think I will opt for the Moller.
I had a anchor stolen several years back I admired with amazement the clean cut that was made in the line when they took it and the chain it was attached to. And several batteries, gas tank hoses, lines, ...I will say if a boat is on a body of water where aircraft fly over, in and out of a airport like mine was stored and thieves steal anything that disables that vessel, gas, battery, gas line ect so it can not be used in a emergency water rescue, That type crime should be a federal felony.

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Author	Topic: 1987 Montauk Stock Seat Height for Fuel Tank
queenfish	posted 12-07-2013 02:29 PM ET (US) We own a 1987 Montauk that we keep down in Baja and it needs new fuel tanks. We can't really measure them since it is a thousand miles away. Does anyone know the exact dimensions of the space under the stock seat? Has anyone else replaced their tanks with some of the stuff now available? Please. Thanks. Mark
DVollrath	posted 12-07-2013 03:18 PM ET (US) Mark, The Mirax D-1212 tank is made for a BW Montauk. It's measurements are 12(h) x 14(w) x 18.75(l). I don't believe this includes the fill neck & cap on the height, nor the handles on the length. These tank fit perfectly in the mats under the RPS. I have a pair on my 1988 Montauk. The fill assembly is perhaps 1.5" higher than the top of the tank body. I can take exact measurements in a week or so, but the above numbers are reasonably accurate. Dennis
The Chesapeake Explorer	posted 12-07-2013 08:36 PM ET (US) My 1987 Montauk is height from deck to bottom of seat 14 3/4" There is the hole in the deck for the fuel line with a oval trim ring around it. The oval trim ring is 1/4 inch high. This is right below the seat to the rear center. The red mats are 1/4 " thick where the tanks sit. Width of both red gas tank mats 31.5 " This is the space between the seat supports on the port and starbord sides.This includes the space between the tanks Lenght of red Gas tank mat 21.5 " This is how wide from the front of the boat to the rear the mats are. The seat is about 19 inches wide, the gas tank mats are longer then the width of the seat they stick to the rear about 2 inches and are lined up with the seat to the front. The gas tank mats have a edge about 1/2 inch wide all around so 1" would be subtracted to fit within the gas tank mat front to rear. Useually when a large 24 gal tank is placed the edges of the mat are cut/trimmed so the tank will go in, or the mats are removed by drilling out the pop rivets that hold them, Mine are in rough shape as most will be with 26 years age. Bottom line 14 3/4 high 31.5 wide 21.5 deep is the size of the area less a bit for clearence a 1/8 -1/4 inch The mats are 21.5 X 14 wide total including the edge and will take a tank 12.5 wide and 19 long if you are using seperate tanks with 14 1/2 from the mat surface to the bottom of the seat for total tank filler or fuel line fitting height and 14 1/2 tall would be scraping the bottom of the seat. Now the hole for the gas line in right under the seat on mine, This can differ as to where the dealer put it. Many of the big tanks will go over this hole, some have a divot in the tank so the hose can go in the original hole, others you may have to drill a new fuel line hole to the tunnel. I really wish tank makers could get this right.
The Chesapeake Explorer	posted 12-07-2013 08:48 PM ET (US) Some explaination between the sizes on tanks on the post above mine. As I state the mat size for a tank is 12.5 X 19 . Now this would be if you had a rectangle tank that sat right into the mat with side that went stright up. The steel 12 gal Long Cruise tanks, which I had for 25 years were a bit wider then 12.5 inches but they are round on the edges side to side not square. They fit in the "footprint" of the 12.5 X 19 dimension as the radius of the tank comes over the sides of the mat edge. Other tanks with rounded edges may be simular. The 31.5 width is the max size for tanks side to side to the seat supports.
frontier	posted 12-07-2013 10:41 PM ET (US) Take a look at the Moeller #031626 fuel tank. Specifically designed for use under the RPS in a Boston Whaler Montauk. Rear slanted gas cap makes it easy to fill without moving the tank. Fuel hose floor opening works fine - I just cut the factory plastic surround piece so the tank lays flat. No tank mats necessary. We've used several over the years including in our current classic Montauk. Works great.
The Chesapeake Explorer	posted 12-08-2013 10:14 AM ET (US) My 12 gal steel Long cruise tanks were great, they fit perfect and lasted a long time, finally they developed pin holes in the bottoms all though I painted them and glassed the bottoms. Last year the last one went to the dump. I wish they still were made. They were about 90 dollars each A bit less the cost today as the Mirax with inflation . I have a couple of plastic tanks a 3 gal and a 6 I got both cheap on sales.The 3 is a extra tank that I grab if Im going any distance. I now use the 6 and a old Evinrude steel 6 gal tank that came with my original motor. Plus the 3 gal. I have long thought of a big 24-27 gal tank I looked at the Pate some time ago, they developed troubles with ethanol gas. The Moller as described above is a nice tank I have considered that one and will have to place a new fuel hose hole in the deck if I ever go with that. A couple of issues I have , had has me sitting it out with the plastic cheap tanks, One is that fuel does not keep very long and goes stale faster then in the past. I have gone out and had sour fuel stop me and changed tanks got back then had to drain out the bad gas and burn it off in my old truck little by little, a hassle. Gas stabilizer does work but its also not cheap. The Mirax tanks are similure to my original Long Cruise, and are very nice looking, they are also expensive as they are high quality and custom made. They can be removed easy and drained of gas if the boats sitting a while. This is a advantage to the Mirax tanks. With the price of gas today , Montauk tanks are easy to steal hence with the Mirax tanks there goes gas plus expensive tanks and thats a disadvantage. The Moller would be hard to steal as its big, but it can be done and with even 15 gallons in it, would be satisfying work for a thief. Of course its size makes it difficult to just pour out the gas into say a 5 gallon bucket then funnel into a thieves car. Perhaps a nice gas thief will simply siphon off the gas and leave the tank which would be Ok with me. When I get tired of my current tanks I think I will opt for the Moller. I had a anchor stolen several years back I admired with amazement the clean cut that was made in the line when they took it and the chain it was attached to. And several batteries, gas tank hoses, lines, ...I will say if a boat is on a body of water where aircraft fly over, in and out of a airport like mine was stored and thieves steal anything that disables that vessel, gas, battery, gas line ect so it can not be used in a emergency water rescue, That type crime should be a federal felony.