Yet another auxillary question!

[steviecops]

I fitted a drop down type auxillary bracket on my boat today ready to take my Johnson 9.9 auxillary engine. However, when I hung the engine on it, it seemed like a lot of weight to have hanging off the back of the boat on a bracket. My motor weighs 77lbs, but with the bracket holding it between 12 and 16 inches away from the transom, the leverage on the transom must equate to a lot more than 77lbs.<br /><br />I'm worried about the stress being put on the transom. The boat is a 17ft long tri-hull, (cathederal hull), and weighs around 1000lbs. My main engine is a Johnson 55.<br /><br />I'm now thinking of buying a 6hp! Would the weight be that different, and what would I lose in speed compared to the 9.9?<br /><br />Thanks for your advice, and sorry to keep bleating on about these auxillary motors!<br /><br />Steve

 

[walleyehed]

Re: Yet another auxillary question!

The weight of the engine would of course depend on who's 6hp you're talking about.<br />The important item of mounting would be that the bolts used are sufficient and if needed, a backing plate installed to distribute the torsional load.<br />Speed difference? don't know what that may be, but you don't want to get so small you have to run it at WOT to move at a good clip.

 

[Scaaty]

Re: Yet another auxillary question!

The bracket should be rated for 15hp. Most are. Like Walleyehed said, ya got to back that puppy up in the transom. Not the bottom bolts(use Stainless bolts)as they push against the transom, but the top bolts. Need something inside. I have a 12 inch 2x4 backing it up with big washers on my 20 foot 5hp kicker. The bigger the better. <br />And one more thing to make you think even 2 hp is too much....when you start up that 9.9, its the weight now, PLUS the torque levering the boat out of the water, so you MUST back up those top bolts. Keep us posted

 

[steviecops]

Re: Yet another auxillary question!

Thanks for that good advice. I was thinking maybe I should get something behind those bolts. There are eight bolts holding the bracket on, the bottom two come inside the boat underneath the splash well, so I could only get a plate behind the top bolts anyway.<br /><br />How about something on the outside under the bracket itself? Would that be a good idea?<br /><br />Thanks<br />Steve

 

[walleyehed]

Re: Yet another auxillary question!

It won't hurt the transom any, but it won't help the bracket support the weight, as the torsional load is pivoting at the base of the bracket.<br />Just make sure the top is secure and that's where I'd support the inside so the bolts don't overload the material.

 

[steviecops]

Re: Yet another auxillary question!

Thanks walleyehed, I'll do as you suggest.