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1982 Boston Whaler Repower with Yamaha 40 4-stroke

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1982 Boston Whaler Repower with Yamaha 40 4-stroke

Old 08-22-2016, 07:32 AM
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Default 1982 Boston Whaler Repower with Yamaha 40 4-stroke

Hi All - I am looking to repower my 1982 13-foot Boston Whaler this winter with a new engine. The existing engine was a 1982 Mercury 40hp and I am looking to potentially repower with a Yamaha F40 four-stroke. I am thinking this is a job I can do myself but want to make sure I get all of the correct components.

Any tips and tricks from others who have completed a repower like this would be much appreciated.

Thanks!

Last edited by Agoldsc; 08-22-2016 at 07:34 AM. Reason: 13 foot Whaler - My mistake for not including.
Old 08-22-2016, 07:33 AM
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Ari,

What size/length Whaler?
Old 08-22-2016, 07:34 AM
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13-foot. My mistake for not including.
Old 08-22-2016, 08:07 AM
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Definitely can be a do it yourself project on the little engines as there is not much to them. You will have to have a certified dealer do a PDI inspection on it and register the warranty. You should also consider the 40 Merc 4-stroke, incredibly light weight at 214 pounds and a very good match on the 13 (we have repowered several of them). You may even be able to reuse your existing rigging to save costs there if it is in decent shape.
Old 08-22-2016, 08:09 AM
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I would not put any current 40 HP motor on the transom of a 13 foot Whaler of that era. They are all too heavy. Ideally, about 160 lbs is about maximum weight that should go on the transom of a 13 footer. Your Mercury 40 weighed about that.
Old 08-22-2016, 08:40 AM
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Originally Posted by Whaler27 View Post
I would not put any current 40 HP motor on the transom of a 13 foot Whaler of that era. They are all too heavy. Ideally, about 160 lbs is about maximum weight that should go on the transom of a 13 footer. Your Mercury 40 weighed about that.
So what engine would you repower with then? 30HP?
Old 08-22-2016, 08:50 AM
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Here are photos of one with a 40 4-stroke, fuel tank and battery in the stern, didn't self bail but most don't anyways. Putting the fuel tank under the front seat makes a huge difference in how the boat sits in the water too:


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Old 08-22-2016, 08:51 AM
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Originally Posted by Agoldsc View Post
So what engine would you repower with then? 30HP?
Coming from a 40 2-stroke, you will not be happy at all with a 30 4-stroke power wise. This boat is just so perfect with a 40.
Old 08-22-2016, 08:58 AM
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Originally Posted by sundancekid View Post
Coming from a 40 2-stroke, you will not be happy at all with a 30 4-stroke power wise. This boat is just so perfect with a 40.
Could you rig it so the battery and fuel tank are under the console/seats?
Old 08-22-2016, 08:58 AM
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Originally Posted by sundancekid View Post
Here are photos of one with a 40 4-stroke, fuel tank and battery in the stern, didn't self bail but most don't anyways. Putting the fuel tank under the front seat makes a huge difference in how the boat sits in the water too:


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Very stern heavy. The 13 footer does not slice waves so overweight conditions on the transom are not good for anything but flat conditions. Fuel tank and battery should be moved forward.
Old 08-22-2016, 09:02 AM
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Originally Posted by Agoldsc View Post
Could you rig it so the battery and fuel tank are under the console/seats?
To counter balance the 220+ lbs you'd probably have to move the fuel tank to under the thwart seat and battery under the steering console.

The 13 foot Whaler was designed in the late 1950s and just wasn't designed to take a 200+ lb outboard. Back in the late 1950s a 35 to 40 HP outboard weighed about 130 lbs.

To answer your question, I would pick a motor that came in at about 160 lbs which means 30 HP. I think the E-TEC 30 is going to be the strongest as it has the most displacement of all 30s and its a 2-stroke. Other options are to find a used 40 2-stroke or rebuild what you have if you need 40 hp.
Old 08-22-2016, 09:26 AM
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First of all, aren't the 40 hp Mercs made in CHINA? I would forget that crap right away.

Second, this is a little utility boat. It will plane out OK with 15 hp. I used to have a whaler with a 40 hp two stroke, and you would need glass smooth water to use that power.

When the bottom rotted out of the 40, I switched to a 25 hp two stroke, which I consider to be an ideal motor for that boat. Planed out great, and would do about 25-30 mph, which is plenty fast enough for this type of boat.

BUT, the gov won't let us buy that motor anymore, so if it were me, based on having actually owned and operated a 13 whaler for about 15 years, in all different conditions, including bay and ocean, light and heavy winds, I would go with a 25 hp fuel injected engine. The carbs gum up too easy for the ethanol based fuel. Maybe you could go with a 30- but you would need to move the battery and fuel way up in the boat.

Too much weight on the stern of this boat will make it useless as an open water boat.
Old 08-22-2016, 09:37 AM
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Also, if your whaler needs to be repowered, now may be the perfect time to get rid of it and get into a 15 hobie power skiff. That is what I did, and the hobie can do anything the whaler can do, and more. It rides like a little Seacraft, and goes just fine on a 25 hp two stroke, although it wants a little more hp. It's a night and day difference from the whaler, and similar cost, but a little hard to find.
Old 08-22-2016, 10:03 AM
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The 20 inch shaft length Yamaha has a nominal weight of 214 pounds. The weight shown for the Mercury 40 HP four stroke with a 15" shaft length is 216 pounds.

Published weight of a Mercury 40 HP two stroke is shown a 171 pounds. A difference of 43 pounds from the Yamaha. Get yourself a 50 pound bag of sand and gently lay it on the top of the motor you have. See how the boat sits in the water. If you think the boat sits ass heavy, and if the battery is in the rear of the boat, move it forward to see how the boat now sits. A group 24 battery weighs about 45 pounds. Moving the battery forward can easily offset the added weight of a new motor. Then too you can move the gasoline tank forward if you want.

Regarding installation of a new motor it is not a big job in the scheme of things. Hang the motor on the transom, install the new control box, connect the throttle and shift cables to the new control box at one end and to the motor at the other end, run the electrical harness from the control box to the motor and connect it to the motor, connect the battery cables to the motor at one end and to the battery at the other end, and finally connect the fuel hose to the motor. Now if you want gauges they would have to be installed with a wire run back to the motor and another wire run to the key switch.

If you want information from someone that has done exactly what you are proposing to do, head on over to http://continuouswave.com/forum/inde...032dee26d5ec0a and do a search there. I recall reading about a boater that installed a Yam F40 on his BW.
Old 08-22-2016, 10:06 AM
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Originally Posted by Time Machine View Post
First of all, aren't the 40 hp Mercs made in CHINA? I would forget that crap right away.
If a Mercury Motor made in China is made to Mercury's specifications there will be no difference between a Chinese made Mercury and a Fond du Lac made Mercury. Call Mercury Marine and see what they have to say.
Old 08-22-2016, 10:13 AM
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BS we have two 13ft whalers one 1960 and the other a 1990 both have new 4 stroke yamahas and my boss also has a 4 stroke 40 on his 1980

I run airplane batteries and a custom fuel tank under the front seat to offset the weight. but the boat sits the same in the water with the 40 it has now as it did with the old Evenrude 50 it had on it. doesnt really matter when i get my 270 pounds in it anyway

you should be able to mount it yourself

first pic is my 1990

the other two are my 1960 Before i had the custom fuel tank added, and im sure there is water in the back in those pics as well as i didnt add the bilge pump till after the fuel tank
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Old 08-22-2016, 10:16 AM
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Originally Posted by alloyboy View Post
If a Mercury Motor made in China is made to Mercury's specifications there will be no difference between a Chinese made Mercury and a Fond du Lac made Mercury. Call Mercury Marine and see what they have to say.
Could not care less what Merc has to say about it. If the motor has a made in China sticker on it, and there are alternatives, I will go with the alternative because China is the adversary of the US. Google "south china sea".
Old 08-22-2016, 10:23 AM
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Originally Posted by bhales View Post
BS we have two 13ft whalers one 1960 and the other a 1990 both have new 4 stroke yamahas and my boss also has a 4 stroke 40 on his 1980

I run airplane batteries and a custom fuel tank under the front seat to offset the weight. but the boat sits the same in the water with the 40 it has now as it did with the old Evenrude 50 it had on it. doesnt really matter when i get my 270 pounds in it anyway

you should be able to mount it yourself

first pick is my 1990

the other two are my 1960 Before i had the custom fuel tank added, and im sure there is water in the back in those pics as well as i didnt add the bilge pump till after the fuel tank
That boat is sitting WAY stern heavy. With a light motor, the boat will go on and off plane very easily, and can run on plane at lower speed. If you go out in a little rougher water, this makes a huge difference. If you have only ever run the boat loaded up like this, you would not have seen this difference.

Plus, it looks like a nice wave could just wash over the stern.
Old 08-22-2016, 10:33 AM
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FWIW, I'm running a '99 35 HP two stroke, on a late 60's 13' Sourpuss model.

It scoots w/ one, can't get on plane w/ greater than 3 people on board.
Old 08-22-2016, 10:43 AM
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Originally Posted by pgkeating View Post
FWIW, I'm running a '99 35 HP two stroke, on a late 60's 13' Sourpuss model.

It scoots w/ one, can't get on plane w/ greater than 3 people on board.
For more than 3, your gonna need a bigger boat.

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