Hello Rustic Charm,
Been through the process of changing motors over on a couple of our boats now. There are a few things you need to mindful of when considering what motor
to put in other than what had already been raised. Idealy you swap out for the identical size and footprint. If not here are a few things that we were not aware of till after we had pulled out our first motor
1) We upgraded our old 27 HP Yanma (which was no longer in production) and went to a 40HP. The old motor while adequate was to small for the boat. Rough rule
of thumb allow 1HP for every foot of boat.
2) Ensure that you motor is matched to the gearbox
3) While your old prop may match your current
prop you will need to ensure it matches whatever you end up. Any of the major aussie prop manufactuers will only be happy to assist from my experience.
4) We found that as we increased the size of the motor the footprint of the motor was larger and hence we had to increase the engine bed
mounts which required a shipwright to do the job to a saftisfactory level.
5) The water
inlet also had to be inreased as well as the exhaust
size when then entailed making a larger hole at the exhaust
hole in the hull
6) The exhaust outlet on the new motor was in a different location to the old motor and we had to have a pipe fabricated to fit in the new position.
7) New motors normally come with new electric
starter panel and wiring
harness. Ensure that your old electrics are compatable with the new motor. A lot of our electrical
items had been sleeved into the old motor wiring
harness IE exhaust fans and these were disconnected by the mechanic
and not reconnected when re-installed.
8) When we finally took the old motors out we took the time to remove old redundant wiring etc then cleaned and painted the engine bay. When the motor is out its a great time to do any modifications required.
9) On our last adventure swapping motors out the actual cost of having a proffesional mechanic
was very affordable and time efficient.
10) Nearly forgot something important. Acess to remove and install a new motor and gearbox
. We were very fortunate that this was pretty straight forward in our circumstance but I have seen first hand cockpits having to be cut open to remove and replace the motor and then repaired when the job is completed.
11) Check the size of the alternator
coming with the new motor. Some come with one that is just sufficient for the job. We found as a rule
of thumb that a 100 amp model will suffice in most instances.
12) For future ease of maintenance
check ease access for changing water
impellor access. Some motor models are just ludicrous. Also check ease of replacing alternators, water pumps etc.
Hope this is of some interest and assistance.
Greg and Sue
Currently Hervy Bay Queensland