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Outboard size

Aug 17, 2013
621
Grampian G26 Ottawa/Gatineau
Hey everyone my lehr 5hp just blew a seal and the mechanic tells me it wont be easy to find so I’m looking at other outboards on the market, my yacht club told me they have 3 for sale, a 15, a 20 and a 40.
I know the 20 and the 40 will definitely be too big, but will a 15 4 stroke be good or will it be too big for my Grampian 26?
 
Jan 11, 2014
7,840
Sabre 362 113 Fair Haven, NY
Yes, a 4 stroke 15 HP motor will be too big due to weight and torque.

When your boat was built, 2 stroke engines were the norm, these are about 20-30% lighter than a similar sized 4 stroke. The transom and the motor mount are probably not designed to support the loads.

As I understand it, the Lehr's are basically Tohatsu motors modified to run off propane. Parts for a 5 hp 4 stroke Tohatsu may fit, except for the carbonation system. Ask your mechanic to cross reference or do some more research on your own.

A 6 to 8 hp 4 stroke will be perfect for your boat. My old Tanzer 22 had a 6 hp 2 stroke and I was never at a want for power.
 
May 24, 2004
6,793
CC 30 South Florida
A 15HP 4 stroke would likely be too heavy. Check the motor mount for maximum capacity rating. They are rated either in weight capacity or if older in Horsepower, but those older mounts considered the horsepower of a 2 stroke engine which were a lot lighter than today's 4 stroke engines. Always go by weight. Seeing how the motor mount is attached to the transom and transom flex will be the last determination for weigh capacity. The motor mount and transom does not only need to be able to handle the engine's dead weight but it also needs to be able to handle the increased load imparted by acceleration forces imparted during motion by sea conditions. I test a motor mount installation by hanging a weight that exceeds the engine weight by 50% and observing how it acts as well as how the transom reacts. Another consideration is being able to remove the engine from the boat. Once you exceed 80 lbs that engine is likely stuck to the boat.