Twin tin

[Lowe 2070 CC]

As speed increases so does friction resistance from air and water. Normally you have to roughly quadruple hp in order to double speed as more power is being used to overcome the increasing resistance (wind in your face). I would hazard that a single 30hp motor would likely give more top end than your two 15's but without the "Cool" factor of the twins.

 

[PSG-1]

As speed increases so does friction resistance from air and water. Normally you have to roughly quadruple hp in order to double speed as more power is being used to overcome the increasing resistance (wind in your face).

Maybe that's what these guys were thinking:



LMFAO!! :mrgreen:

I would hazard that a single 30hp motor would likely give more top end than your two 15's but without the "Cool" factor of the twins.

Yeah, like I said before, twin engines means even more maneuverability, not to mention the 'cool factor' 8)

 

[Lowe 2070 CC]

Maybe that's what these guys were thinking:



LMFAO!! :mrgreen:



Now that's cool (and maybe a little overkill). At what point does a nice inboard make more sense? I've run five 300's on a 37 footer before, but never 8!

7 Marine is producing a 557hp outboard for multiple outboard setups.

From their site "Vessels with multiple outboards don’t ever see the true horsepower produced by those motors. An outboard’s lower gear case is a source of drag, which means that a single outboard is actually the most efficient setup. Each time you bolt on another motor you add horsepower but you also add underwater drag. So the actual percentage of gain in horsepower decreases with each additional powerplant."

 

[1993 Sylvan]

I really appreciate everyone's complements and suggestions. So what you are saying is that I need 2 more 15's on the back.
In all seriousness though currently both motors have a 9x9 prop would the speed increase be that significant with a couple of 9x11's?

 

[1993 Sylvan]

More of the deck

 

[jacobxrt]

I really appreciate everyone's complements and suggestions. So what you are saying is that I need 2 more 15's on the back.
In all seriousness though currently both motors have a 9x9 prop would the speed increase be that significant with a couple of 9x11's?

My 1992 Mercury 25hp had a 9x13 on a 12' jon and it ran 35 on glass.

 

[PSG-1]

I really appreciate everyone's complements and suggestions. So what you are saying is that I need 2 more 15's on the back.
In all seriousness though currently both motors have a 9x9 prop would the speed increase be that significant with a couple of 9x11's?

11 pitch will give more top end, but less hole shot. Also, a higher pitch may be more susceptible to cavitation than a lower pitch.

 

[BrazosDon]

The best I can do is 3 18hp's('70 Evinrude,'61Johnson, '57 Evinrude)

 

[1993 Sylvan]

The best I can do is 3 18hp's('70 Evinrude,'61Johnson, '57 Evinrude)

That would definitely be a project and a head turner. Trips on a tin

 

[1993 Sylvan]

I really appreciate everyone's complements and suggestions. So what you are saying is that I need 2 more 15's on the back.
In all seriousness though currently both motors have a 9x9 prop would the speed increase be that significant with a couple of 9x11's?

My 1992 Mercury 25hp had a 9x13 on a 12' jon and it ran 35 on glass.

35 in a 12 footer thats BA! How was the take off? Mine is pretty torquey... Jumps right up on plane I might be able to go a few pitch's up I just wonder how worth it it is. Where did you get a 9x13 and was it stainless?

 

[jacobxrt]

I really appreciate everyone's complements and suggestions. So what you are saying is that I need 2 more 15's on the back.
In all seriousness though currently both motors have a 9x9 prop would the speed increase be that significant with a couple of 9x11's?

My 1992 Mercury 25hp had a 9x13 on a 12' jon and it ran 35 on glass.

35 in a 12 footer thats BA! How was the take off? Mine is pretty torquey... Jumps right up on plane I might be able to go a few pitch's up I just wonder how worth it it is. Where did you get a 9x13 and was it stainless?

I swear!!!! It was way overpowered but the boat was so old it did not have a U.S.C.G. plate on it so i said what the heck. It would get swamped on choppy days, but ran like hell when it was going. And the 9x13 was what came on it, and i got another one from a propeller shop in my area. He moved to Florida, but he was doing it for 30+ years, and designs all of turning points props. I took his adivice on a new prop, and i'm glad i did. BTW it was a standard aluminum prop, and i had trim tabs on my boat because of pourpoising.

 

[PSG-1]

Here's a story about overpowering:

my girlfriend used to have a 12 foot tracker. It was rated for a 6HP, we put a Yamaha 15 HP on that boat. At slow speed and on moderate plane, it was OK, but if you punched the throttle, it would get really squirrelly. I never held it at WOT, it scared me too much to try it....and being on the water for 30+ years, it's rare to hear me say I'm scared of horsepower on a boat. But with that boat, I was.

Anyhow, she used to keep the boat tied up to the dock at the restaurant where she works as a mariculture permit manager. She went down there one morning, and the boat was covered with mud and blood, and had a good bit of water in it. There was a LOT of blood. Definitely not the way she left it. It had been stolen the night before, but then returned. As such, she reported it to the sheriff's department, in case someone was seriously injured, based on the amount of blood all over the boat.

We never found out exactly what happened, but I think I can surmise. Some drunk or crack head stole the boat in the middle of the night (low tide) and went out for a joyride. One of 3 things happened. Either they hit the throttle and it got squirrelly, chine walked, and pitched them out. Or, they let go of the tiller for just a second to open their beer or get another hit off their crack pipe, and when they turned it loose, it locked in the corner, and pitched them out. Or, they were running out there at low tide, hit an oyster bed, and got pitched out.

Whichever scenario it was, I call it fitting karma. Steal somebody's boat, get F-ed up. Apparently it messed them up and scared them so bad, they brought it back! Now, that's pretty bad when a thief returns something saying "here, you can have it back!"

LMAO!! :twisted: :mrgreen:

 

[RAMROD]

LOL! Good story!

 

[painlesstom]

Another nice aspect of running dual motors is knowing if one breaks down, the other could get you home.

Cool boat. 8)

 

[PSG-1]

Another nice aspect of running dual motors is knowing if one breaks down, the other could get you home.

Most definitely. Also, if there's an issue with the steering, if you have seperate throttle controls, you can make it back home even with the steering completely disabled. Again, by simply speeding up one engine and slowing the other one down, you can turn the boat almost as easily as by turning the steering wheel.


I remember when the steering nozzle bracket broke on my Sea Doo speedster, after it initially sent me flying into the marshgrass, :shock: I was like "WTF?" until a quick inspection I revealed what had happened. Corrosion had weakened the nozzle bracket, and I neglected to see that, and paid for that mistake.

Once I realized the nozzle bracket had broke, I brought it back to the ramp with no steering control whatsoever, just varying the throttle on the 2 engines. And with a valuable lesson learned...frequently inspect every component of the steering system on a jetboat!

 

[1993 Sylvan]

Agreed the peace of mind of twins had me sold right from the first time I took her out. The newer motor that I had just bought threw the impeller pin that keeps it locked to the gear shaft making the motor stop peeing because the impeller was just spinning around the shaft not with it. I only noticed after it started to smoke some and figured something wasn't right and killed it. Luckily I had the other to get me back to the dock. A new impeller kit and it purrs like a kitten again.

 

[1993 Sylvan]

I reinforced the second part of the front deck with some alum and added some foam as well