downsides to twin outboards...

tod osier

tod osier

Well-known member
Supporter
I have been toying with the idea of putting twin outboards on my tollman if I could get a real good deal on a pair, I have a year or two to keep my eyes open. What I need for power would be in the 75-115 range depending on what model I build.

I would love the security of twins with seperate fuel and battery systems. What are the downsides? You lose some hp due to drag for the second lower unit (how much HP?) and I assume to set them up you would need to have a more expensive set of controls (how much $$$ and trouble???). More weight on the transom too (380 for a yamaha 90 hp vs. 500 for 50 hp twins). I don't think the smaller motors can be set up to counter rotate, so it torque a problem? Anything I'm missing?

A pair of 40s or 50s would be sweet.
 
More fuel?
Click to expand...


Good point, but I'm not super concerned since my 4-stroke 40 just sips the fuel. I can run all day on 3 gallons, so the differance between 2 50's and a 90 wouldn't be so much, especially since I'd be burning 10 gallons of gas to get to the coast :(.
 
Would the tolman have under-deck fuel cells or external tanks? Just curious how you would setup seperate fuel. Two interal tanks or two external?
 
Would the tolman have under-deck fuel cells or external tanks? Just curious how you would setup seperate fuel. Two interal tanks or two external?
Click to expand...


If I was running a pair of 40s or 50s, 6 gallon portables would be a great choice IMO. Portables can be cleaned, changed, etc, especially given the problems people have with todays fuel.
 
Makes sense Tod. If transom weight is an issue, you can always have a large primary and a kicker (15-25hp) to limp you home.
 
If one breaks down, wouldn't you tilt the non working motor up? I'm not a fan of built in tanks either. It seems like if you get bad fuel, it would be better to dispose of 6 gallons rather than 20-30 and have to clean a big fixed tank. Dual controls are pretty expensive but you can always hunt ebay for a set. I think there are counter rotating lowers for most motors 50 and up. I would definitely try to get counter rotation on them as I think they feed each other water at speed. Personally, I'd stick the biggest single motor on and get a 25 kicker...depending on the size of boat...24'?
 
If one breaks down, wouldn't you tilt the non working motor up? I'm not a fan of built in tanks either. It seems like if you get bad fuel, it would be better to dispose of 6 gallons rather than 20-30 and have to clean a big fixed tank. Dual controls are pretty expensive but you can always hunt ebay for a set. I think there are counter rotating lowers for most motors 50 and up. I would definitely try to get counter rotation on them as I think they feed each other water at speed. Personally, I'd stick the biggest single motor on and get a 25 kicker...depending on the size of boat...24'?
Click to expand...


A single makes most sense money wise (unless I got a real good deal, it woudl be like 2-3-4K more to do twins). Boat size would be 20-24'.
 
I like Harker's idea.

I suspect weight is the biggest thing, plus dual maintenance, etc.

I can only speculate at the moment, but isn't the dual motor setup mostly for torque and a redundancy issue (usually for offshore use)?

Twin outboards (especially on a transom bracket) are sexy, but I like the simplicity of a main motor and a kicker. If you keep a primary and secondary fuel source you should gain the emergency use and it also makes it easier to troll slow.

Just my random 2 cents.

Charlie
 
Todd, I don't own twin motors but when I was younger the next door neighbor had two different boats set up with twins. One had two twenty five horse Evnrudes and the other had two thirty fives. They were used primarily for water skiing. They put on water skiing shows. With twins you have a little more speed but not enough to justify a second motor. What you do have is power. An incredible hole shot. It will take you off the back of the boat if your not hanging on. The boats had external gas tanks. The controls were side by side. As I recall the gas were in the middle and could be operated with one hand. Shifters to the outside. Key in the rear. Only one time did one of the motors quit,ran out of gas. With a long enough boat I don't see the weight of the motors being a problem.
 
I like Harker's idea.

I suspect weight is the biggest thing, plus dual maintenance, etc.

I can only speculate at the moment, but isn't the dual motor setup mostly for torque and a redundancy issue (usually for offshore use)?

Twin outboards (especially on a transom bracket) are sexy, but I like the simplicity of a main motor and a kicker. If you keep a primary and secondary fuel source you should gain the emergency use and it also makes it easier to troll slow.

Just my random 2 cents.

Charlie
Click to expand...


Thanks Charlie,

I was looking for the redundancy especially/particularly for light duty offshore use. There are big fishies out there that I am lusting for.

A kicker is great, but you aren't going to move a 20'+ boat real well over swells with it. Any kicker over a 10hp will reach hull speed pretty quick on flat water, but I doubt they would have the power to move the boat against much rough water when you really really need it.

T
 
You may be surprised, I know you don't like Yammies but they had one with a "High thrust" lower and prop. My thoughts about a 25 or 30 kicker was....they just don't seem to have problems like a big fuel injected, electronic filled motor with all the doo-dads. Redundancy is a good thing on water that will take you to another country though.
 
Tod,

Since it's your money, I like the idea of the twins. Each one should be able to get you up on plane so fuel consumption is reasonable. The numbers, both weight and money seem pretty close when you add a kicker motor, bracket and controls into the equation for the single big OB. The 4 stroke 9.9 adds a hundred pounds back and a quick two grand to the cost. With respect to gas, I'm not sold on the value of separate systems but a selective twin tank set up that would let you rotate gas for freshness and maintain trim if required (pull it from the side I'm sitting on first) would be sweet. Each motor could be set up with it's own water separator/filter for redundancy. (I do like spending someone else's money.)

Scott
 
You may be surprised, I know you don't like Yammies but they had one with a "High thrust" lower and prop. My thoughts about a 25 or 30 kicker was....they just don't seem to have problems like a big fuel injected, electronic filled motor with all the doo-dads. Redundancy is a good thing on water that will take you to another country though.
Click to expand...


But my thought is that chokling down a 90 plus a 25 would be like buying 2 50s. I agree that a high thrust lower unit would be a good idea on a kicker.

You would know better than I, but dont' all motors have electronic doo-dads in them? My pull start yamaha 40 has a computer.
 
Tod,

Since it's your money, I like the idea of the twins. Each one should be able to get you up on plane so fuel consumption is reasonable. The numbers, both weight and money seem pretty close when you add a kicker motor, bracket and controls into the equation for the single big OB. The 4 stroke 9.9 adds a hundred pounds back and a quick two grand to the cost. With respect to gas, I'm not sold on the value of separate systems but a selective twin tank set up that would let you rotate gas for freshness and maintain trim if required (pull it from the side I'm sitting on first) would be sweet. Each motor could be set up with it's own water separator/filter for redundancy. (I do like spending someone else's money.)

Scott
Click to expand...


I need this boat more than ever because someone won't take me out anymore. I'm not super sold on twins, but if I could find a GOOD deal on the right motors.... It sure would give an extra margin of comfort.
 
Todd,
My good friend has the franchise tow boat buisness for this area of long island sound. Think Watch hill reef and all of fishers island sound. He is using his first twin powered outboard aluminum hull with inflatable collar. All the rest of the fleet is single inboard diesel with jack shaft to a stern drive.
All the old boats will be traded I can tell you. The outboard pair of hondas cost 20 G less to install, and you can not tell they are running(Quiet). The big factor is the security of two robust motors on a tow gone bad. The risk involved in salvage in this area is high and the benefit of the pair out weighs the small increase in fuel burn.
In the first tolman book most pictured boats had the kicker, but on the bigger hull I would figure out how to swing two motors. More $ but in the end the benefit will be there.
Check out pontoon boat power because they will have the twin packages in smaller HP due to low drag.
 
How about the best reason NOT to buy 2 motors... "Complexity".

Keep it simple. You take great care of your stuff. You'll buy the best equipment money can buy and you're not an idiot. Buy a nice 90, keep the Tolman light, inexpensive and simple.

BTW, hydraulic steering is awesome, study it.
 
Todd,
My good friend has the franchise tow boat buisness for this area of long island sound. Think Watch hill reef and all of fishers island sound. He is using his first twin powered outboard aluminum hull with inflatable collar. All the rest of the fleet is single inboard diesel with jack shaft to a stern drive.
All the old boats will be traded I can tell you. The outboard pair of hondas cost 20 G less to install, and you can not tell they are running(Quiet). The big factor is the security of two robust motors on a tow gone bad. The risk involved in salvage in this area is high and the benefit of the pair out weighs the small increase in fuel burn.
In the first tolman book most pictured boats had the kicker, but on the bigger hull I would figure out how to swing two motors. More $ but in the end the benefit will be there.
Check out pontoon boat power because they will have the twin packages in smaller HP due to low drag.
Click to expand...


Thanks Bob for your insight, I would love the security of twins.

I didn't catch your point on the pontoon boat packages. Clarify for me?

Thanks,

T
 
We dont deal with them but I see the OEM's at the shows and they have some very cool stuff for the lake boat markets. We chased a pontoon boat down the canal in miami going 60 mph. My point is that they use lower hp twins on many and I am sure that the engine manufactures are catering to the builders to supply twin packages in HP that is not the standard 250 to 150 hp that the Deep V's use.

Andrew the truth is that one motor is much simpler to set up and if maintained will almost always get you where you are going. BUT if you depend on your boat to provide your living, or you operate during times of the year that most tow boat operators are home in bed or florida, twins with dedicated batterys, and fuel will give you a shot at one failure before you have to call for help. The Tolman is a big boat.
As I said the early 18' and 20' was not big enough for the twins, but a 24 is a huge platform and I see no issue with the weight, esp if 8 to 10 gallons are the size of the fuel tanks. Most deep v hulls in that class are carrying over 130 gal of fuel alone.
I know from reading here that Tod is going to be using this thing all year round and in the bad weather. I also know he is not using this for work, but I think the extra cost and small increase in complexity is worth it for a boat that big.
I say this after having spent many hours at sea in charter fishing boats with one single diesel. 70 to 100 mi offshore, we never turned it off at night and you darn well better have a good kit of spares on board.
 
You must log in or register to reply here.
Back
Top