I have '78 O'day 23 with a 5hp 2-stroke outboard. I want to upgrade the engine to a 4-stroke. I believe the boat was originally rated for up to a 15hp, but it would have been a 2-stroke which is much lighter than a 15 hp 4-stroke. I'm looking at a 4-stroke Yamaha 9.9 and wondering if I'll be overloading/over-stressing the transom. Any thoughts??
Outboard Weight
- Thread starter EImarina20B
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Me too. I use an Evinrude sail master 6.6 with a three blade, low pitch prop and she pushes out westward into Lake Huron just fine
I have a 5hp 4stroke Nissan with an aluminum height adjustable Garelick Ez-In motor bracket on mine, and I don't see any problems. And, thank goodness, because I don't want to have to cut an inspection port in the back of the cockpit to put on a new bracket!
I don't know the weight of the motor, though.
Brian
I don't know the weight of the motor, though.
Brian
It's debatable if going from a 2 stroke to a 4 stroke is an upgrade, I did it because my 2 stroke died. The old 7.5HP 2-stroke weighed 85#, the new 6HP 4-stroke weighs 60#. I believe a 9.9 4-stroke will be closer to 85#-95# depending on the features (like electric start).
A motor mount and transom in good shape should have no problem with a modern 9.9 4-stroke. You need to inspect your mount and transom for visible signs of stress (both inside and out), and pull on it to see if there is any give and how sturdy it feels. Your old 5 was probably around 50-60#
I'm amazed that my 40 year old mount held an 85# motor for those many year with no signs of a problem.
A 9.9 is over kill for a 23'. I'm using a 9.9 2 stroke (a 1993 model) on my 25' and that's more than enough to drive the boat to hull speed (around 5.5 K) with power to spare. Boat weight is around 4800+ lbs. Yours is considerable lighter. So 8 HP or even less will be adequate. 8 HP extra long shaft should easily be able to drive your boat into a 25K headwind. My previous boat was an easily driven Sonar (2300 lbs) and a 3.5 HP 4cycle was completely adequate. Before that was a 13,500 lb Ericson with 24 HP disel, but that could have used a couple of more horses when pushing into big wind.. About 2 HP per thousnd lbs is usually adequate
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