What size auxillary motor

[Kiwi Phil]

I am considering getting an auxillary outboard for a 25' Flybridge Cruiser. It weighs under 3.5tons when full of fuel. It is powered by a 305 mercruiser with Alfa 1.<br />I would like to attach the auxillary on one of those fold up attachments you bolt to the stern.<br />I am in tidal waters, so there is a 50/50 chance I will be going against the tide.<br />Has any one done this.<br />Has any one any suggestions for me.<br />Cheers<br />Phillip

 

[Drowned Rat]

Re: What size auxillary motor

Hi Phillip. I assume you want this motor just for emergencies? A 15hp would probably do nicely but a 20hp would be even better. Look to make sure the outboard bracket you get can handle the weight and hp before you decide. Good luck.

 

[62_Kiwi]

Re: What size auxillary motor

Hi Phil - for my 2 cents worth, I would reckon 15hp with the correct prop pitch should achieve around 5 knots (+ or - a few!) ....but you'll never know how it will perform until you try it. It's a good idea to have a backup (Coastguard recommends having more than one means of moving the boat), but it does of course add a little extra maintenance and general hassle to your boating experience... <br /><br />A 4-stroke outboard would be a good idea to avoid having to worry about mixing 2 stroke fuel.

 

[Kiwi Phil]

Re: What size auxillary motor

Yes, this motor is for emergencies. Especially after I had one last week.<br />As the price for 2nd hand outboards does not vary a lot in the 20-50hp range, (and that is within my budget,) will I get a much bigger benefit by going to a 30 or more.?<br />I am aware the bracket has to be up to standard to cope.<br />Any comments welcome.<br />Cheers<br />Phillip

 

[Solittle]

Re: What size auxillary motor

I have not seen any of the fold up brackets for motors larger than 15 hp.<br /><br />I would go with 15-20 hp. A 9.9 hp will work but might not be enough in any kind of wind/current. I had a 9.9 hp on a 27 1/2'er (also flybridge)but I already had the motor when I got the boat. It worked OK the few times I had to use it though. A 9.9 & 15 should weigh the same. Make sure that the motor is a long shaft

 

[Boatist]

Re: What size auxillary motor

Phil<br />I have a 21 foot Aluminum runabout with a 92 inch beam and weight is 2800 lb dry. I have a 15HP Johnson 2 stroke with a 4 blade high thrust prop and it is not enough. Yes on a calm day with no wind or seas it will do 5MPH wide open.<br /><br />Out to sea with a EZ Steer hooked up on windy days it will take a long time to turn into the wind. If you do not get up to speed before starting your turn you may take one swell sideways unless you time it perfect. In large Swells over 7 feet you have to take them almost head on or the bow will push to the side and the motor does not have enough power to correct until the swell passed.<br /><br />What I am saying is I am looking for a bigger motor for my boat and your boat is so much bigger and catches much more wind and take so much more power to turn into a swell or turn between swells.<br /><br />I think you need at least 25 or 30 HP unless your only going to use it in the best of conditions. Even for trolling at 3MPH with a 15HP you will need the perfect high thrust prop and full throttle.<br /><br />Lift bracket for a bigger motor is a problem. I have combined two brackets designed for up to 20 HP and it works pretty good, but not sure it would support a 20 HP 4 Stroke. I have seen a electric lift bracket that says it will lift up to 50 HP but it cost $1000. One more thing get as long a shaft as you can. Mine is a 20 inch and in reverse it sometimes comes out of the water and still on big swells power head barely above the water.

 

[Dunaruna]

Re: What size auxillary motor

Hi Phil, <br /><br />Its a question I was going to ask also. I have a similar size boat to yours and, like you, I thought a 15hp would be to small.<br /><br />My bracket is rated to 15hp. I've found some rated to 25 hp. They are all mail order sites. Hope this helps.<br /><br /> 25hp bracket <br /><br /> 25 hp bracket <br /><br /> 20 hp bracket <br /><br />Aldo

 

[Kiwi Phil]

Re: What size auxillary motor

Thanks for the replies everyone.<br />It is obvious I am going to need a bigger motor after your experiences Boatist.<br />It is others experiences that count the most.<br />Thanks for the sites Dunaruna. Very helpful<br />I will let you all know how I get on.<br />Cheers<br />Phillip

 

[DJ]

Re: What size auxillary motor

Kiwi,<br /><br />Whoa, 7000 pounds and a high profile boat to boot?<br /><br />Get the biggest engine you casn put on a bracket and the highest thrust gearcase and prop you can get. I would not expect much from anything under a 30.