Do I need counter rotating motors

[timothyl]

In my search for a 75-115 hp motor for my 17.5 seafair Sedan, I have found someone with 2 very nice mid-80's 50hp mercs for a decent price.<br /> Neither of these two motors are counter-rotating. Is it possible to run both these motors on my boat? It sure would solve the kicker motor need.<br /> I have measured and there is plenty of room on the transom and well under the weight requirements of my max hp(165hp).<br /> If this can be done, what items do I need?<br /> <br />I did several searchs and either I typed in the wrong info or this question has not been addressed before.

 

[JasonJ]

Re: Do I need counter rotating motors

You can run them. They aren't of so much power to make the boat undriveable. You'll notice some torque, but it wouldn't be any worse than a single motor that was 100 horsepower. As long as the transom can handle the weight. Two 50s will weigh more than a single 100, but you will probably be okay. Good luck...

 

[ob]

Re: Do I need counter rotating motors

tlands,You may want to consider that the two twin motors in question are under the boats rated hp by a fair margin.This being considered ,your boat will have a difficult time attempting to plane out with just one of these engines in the event that one would fail.Also ,while you could mount the two right hand rotation engines ,not having one of counter rotating direction will impose a bit more difficult steering and could at worse rob some prop bite from the adjacent engine.As a rule the two 50's will also burn a bit more fuel than say a single 100 hp and the added drag of the lower units may require reduced pitch propping as compared to a single of twice the HP.If it were mine,which it isn't,I would opt for a single engine of at or near the boats rated HP.

 

[Jdeagro]

Re: Do I need counter rotating motors

Tlands;<br /><br />I would agree with OB, the added wieght, probable torque list, steering issues are enough to make me shy away from the two 50's. The other things that you would need to consider are additional rigging costs, trying to keep the motors in sinc, and maintenance of two motors. <br /><br />Requarding the torque list, if it is a deep V hull, it is guaranteed. We had some experience in Canada with the police department that had twin 70's on a 22' Zodiac safety boat. They wanted the twins for safety reasons. The boat had a bad list and in rough water (they always run faster than they should) the boat would leave the water off the top of a wave with the port side down. The re-entery was scary because it was also port side down. They have flipped a few boats, but that was more likely exagerated by running too fast in rough water. We fitted the boats with Smart Tabs to compensate for the handling issues.

 

[grandx]

Re: Do I need counter rotating motors

I'd find a single to do the job, you'll be glad you did. 1/2 maintenace, better fuel economy, much lighter. Unless you can't get enough HP in a single engine, or you are offshore and need duels for safety, you would never want to run a pair.