How much engine/weight can my motor mount handle?

[Ben16737]

Apologies if this question has already been asked ad nauseum, but I did a search and didn't come up with much. How can I find out what size and weight my Capri 22 motor mount can handle? I currently have a 5 horse Nissan, and that's plenty of power but it's getting quite old. It either needs a bunch of work, or I need to replace it. I have a chance to buy a Mercury 9.9 with relatively low hours from a family friend, but I know that would add weight. How much is too much? I know I don't need the extra power, I just don't want to miss out on a good deal.

On that note, I've never purchased an outboard and have no idea what it's worth. How much would you folks spend on a 9.9 with ~100 hours on it?

 

[dlochner]

The motor mount is only one issue, the additional weight on the transom will affect the boat's trim and performance.

A 5 hp 2 stroke Nissan is fairly light. The current crop of 5 hp 4 strokes weigh in at about 60 lbs. An 9.8 hp long shaft Tohatsu weighs in at 84 lbs about double that of the Nissan. A new Tohatsu at Defender is about $2200.

A 3.5 HP outboard would be sufficient for your boat and weigh about the same as the Nissan in the 40 lbs range.

 

[Benny17441]

There is a difference between the weight of similar horsepower engines whether they are 2 strokes or 4 strokes. Motor mounts today are rated by weight handling capacity but years back in the days of 2 stroke engines boat manufacturers uses to rate them by horsepower so a maximum of 4 HP meant the average weight of a 2 stroke engine around 35 to 45 lbs. Since small 2 stroke outboard engines are no longer legally sold in the US you need to go by the weight of the current 4 stroke outboards. I'm afraid a 4 stroke 10HP engine will be tipping the scales at close to 100 lbs. which would definitely be too much for your boat irrespective of whether the motor mount could handle it. We have a 9.8 HP 2 stroke Nissan on a 22' boat but the engine weighs about 58 lbs. Other than pickup it does not make the boat go faster and fuel consumption is much larger. The way I would test a motor mount weight capacity is to see how it reacted to hanging my 200lbs. body weight from it. I figured the horizontal and lateral acceleration forces of a 60 lbs. engine will not exceed 200 ft/lbs. Check for transom flex and motor mount deflection.

 

[jssailem]

Manufacturer’s provide specs for their designs.

Catalina 22 Capri – Catalina Yachts

Reading the specifications the sport model calls for a 4-6 HP outboard.

Varying from the design specs is a boat owner’s decision. The strength of the boat, how it will preform, will all be different than the design parameters considered by the manufacturer.

 

[dlochner]

Reading the specifications the sport model calls for a 4-6 HP outboard.

When the Capri 22 was first built in the mid 80s heavy 4 stroke outboards were non existent. OB recommendations were based on both performance and boats were built to support the weight of a 2 stroke OB. When repowering it is better to use weight as a guide rather HP. A 4-6 hp OB would be pushing the upper limits of the weight range.

Most 4-6 hp OBs come in at about the same weight give are or take a couple of pounds. They use the same engine block and just change the tuning.

 

[Ben16737]

Thanks, all. I decided not to go with the larger motor. I was tempted by the time-saving aspect of it. I knew it was more HP than I need, but strapping a newer, good-running engine to the transom would have gotten me out on the water faster than taking the time to rebuild a carb and whatever else my old engine needs. But doubling the weight supported on that mount just doesn't seem like a good plan. So, time to break out the wrenches and sockets, I guess.

 

[Tedd]

On that note, I've never purchased an outboard and have no idea what it's worth. How much would you folks spend on a 9.9 with ~100 hours on it?

Craigslist is probably your best source of information for outboard motor asking prices. I use searchcraigslist.org, a site that lets you search all of Craigslist with a single query, to gather global data on prices.

 

[Benny17441]

Tohatsu has a 3.5 HP 4 stroke engine which comes in at 41 lbs. their 4 to 6 HP engines are all 55-60 lbs. In my experience the boat with a little squat can handle the 60 lbs. but the question is can the motor mount and transom? Hang a 60# weight from it and forcefully tug on it up and down and sideways and observe how the transom may flex; hopefully not much. If the mount is old and iffy I would look to purchase a new one ( there are adjustable motor brackets which will allow to pull the engine out of the water). When installing use a backing plate in the inside of the hull.