What is the Right Size Motor for a 17-Ft Fiberglass Boat?

- The combined weight of the boat plus motor will be around 1,900-lb.

- There will be 3 men and 1 woman on the boat (around 600-lb).

- I will run the boat in fresh water lakes or in protected sea water (inshore or bay).

- I expect to run the boat at 20-mph cruising speed (land mile, not nautical mile). I don't do skiing. I only use the boat for fishing.

I would like to know how small a motor I can use to satisfy the requirements stated above. I understand that fiberglass center console boats in that size tend to have a 90-hp or 115-hp outboard motor. But I also understand that most people like to run their boat in a very high speed (like 35 mph or 45 mph) that I don't enjoy doing. I am thinking of downsizing the motor to match the relatively low cruising speed that I likely will run the boat at.

Based on past discussion, I am under the impression that an outboard will work the most efficient if it is being run in wide-open-throttle. This means I am looking for a motor that can satisfy the requirements stated above when it is being run in wide-open-throttle (instead of getting a BIG motor and then running it at low speed).

Thanks in advance for any info. And hope people don't mind the fact that I have asked a similar question previously.

I posted a similar message not so long ago about matching a motor with a 18-ft aluminum boat. But I have changed the requirements (18-ft downsized to 17-ft, aluminum changed into fiberglass, ...etc). Therefore, I need to ask around here again. Moreover, my wife wants to run the boat in saltwater from the get go instead of phasing in from freshwater into saltwater (as what I have originally planned). Therefore, I need to get the right gas engine from the very beginning instead of using a small kicker engine to get by.

Jay Chan

Thus, the evidence would seem to show that a 90 ETEC was clearly superior to a 115 hp Yamaha four smoke because it's lighter, quieter, more efficient and probably faster both out of the hole and top end..

Heh, heh, heh.... :>)

Four smokes are doomed - ETEC is the wave of the future!!!

But I will confess to having partaken of the Bombardier Kool Aid. :>)

mmmmmmbombardierkoolaidmmmmmmmmm

With the twin 225 E-TECS on the Contender, we had a 40% decrease in fuel/oil bills.

Jay Chan

http://www.evinrude.com/en-CA/Campaigns/

Enough said four smoke boy. :>)

I had a 70hp on a 15' Whaler CC. It was the perfect size for that boat, as long as I had three or less people aboard. Once I got to four or more, the boat took much longer to get on plane, and the engine seemed to strain.

On a 17' CC, I'd want a 90hp minimum.

Jay Chan

I will likely also take into account of the range of motor size that the manufacturer has bundled in their boats. If they are offering the same boat with both 90HP and 115HP. I will need to make sure I will not go below their range of motor sizes too far, or better yet just stick with their minimum motor size (in this example, that will be 90HP).

Jay Chan

OK, 115HP will be IT!!

Thanks for sharing your experience. This surely helps me to narrow down the selection very quickly.

Jay Chan

-rick-

By definition, efficiency would be when the boat is on plane, trimmed out and running without effort. That is not at WOT throttle - more often it's at 2/3s throttle. On my Ranger for example (it's the closest boat I have to a 17 foot Center Console) it comes up fully on plane around 3,000 rpm at 20 or so mph and settles in (same throttle setting) at 4100 rpm and 30 mph. WOT on this boat is 5500 rpm and 45 mph. At cruise (4100 rpm/30 mph) it eats very little fuel - I can run all day at that speed. The engine is a 200 hp Evinrude FICHT.

Conversely, on my 14 foot Princecraft with a 25 hp Johnson, it planes around 13 mph and about the same throttle setting. However the difference in fuel consumption between 13 mph and 25 mph which is maxed out on that boat is marginal at best - I might as well run at WOT in this boat because I'm not saving anything meaningful.

Be that as it may...

You can certainly downsize the engine and get away with it for the speeds that you are attempting to run at, but it may be that the boat you are considering may not plane efficiently at that speed - or run acceptably.in any kind of moderate wind or sea. I could put a 150 hp FICHT on the Ranger and run it WOT, but what is the savings - nothing.

I know that you are attempting to lessen the economic impact of a boat purchase, but at some point, it makes no sense. The monetary difference between a used 40 horse and a used 90 horse isn't that significant. Considering the engine load you states (people, gear, fuel) I would consider 90 hp the bare minimum.

Additionally, the extra horsepower will help you occasionally get out of sticky situations - and they will happen whether you are on a lake or a salt water bay.