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Thread: Motor question 9.9 to 15 hp 4 stroke

  1. #1
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    Default Motor question 9.9 to 15 hp 4 stroke

    I currently have a 1448 Grumman's flatbottom just bought it a few weeks ago . Boat seems little heavy but doesn't run to bad says 7mph on my GPS. Would like to travel just a bit faster as I fish some bigger lakes and some only have 3 launches and it takes me an hour to get anywhere . Just wondering what improvement in performance I could expect . And how much differance with the 4 stoke compared to a 2 stroke all ive ever was 2 strokes 60 and a 70 so any advice is appreciated thanks.
    Scott
    Life comes at you fast ... Better have a net...

    Scott Beitzel----Western maryland

  2. #2
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    You might want to play with weight distribution.

    I had a 9.8 Merc on a 1448 Semi-V. It would do 17 mph unloaded with just me. When I put the battery in the rear, it was a slug and would barely do 10mph. Moved the battery up front, and the difference was night and day. Would've never thought it could make that big of a difference, but it did.

    Eventually I put a 25 Johnson on it, and it was a rocket. 30mph.

    Not sure what your boat is rated for, but if I was going to through all of the trouble of finding and swapping a motor, I'd go as big as I could. Going to a 15 is not much of an improvement.

  3. #3
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    Whoever had the boat before run a bigger motor as they reinforced the transom with aluminum bracing and such all looks sound and stable . It does have a battery in the rear I was thi king of moving it towards the front as I weigh 275 I do t pack much gear just jigs and worms lol now my 15 yr old son on the other hand weighs 140 but thinks he is Kevin vandam and takes 80lbs of plastic lol.
    .thanks for the advice and I know I gotta get the nose down it wants to rise unless I put the boy in the front ..so adjusting is needed for sure maybe a whale tail on the motor
    Life comes at you fast ... Better have a net...

    Scott Beitzel----Western maryland

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    Quote Originally Posted by scoremaster View Post
    ..so adjusting is needed for sure maybe a whale tail on the motor
    Or a 4 blade prop if you don't already have one....the 4 blade helps lift the rear up and counter heavy loads in the rear like batteries and fuel tanks.

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    Quote Originally Posted by Atimm693 View Post
    Not sure what your boat is rated for, but if I was going to through all of the trouble of finding and swapping a motor, I'd go as big as I could. Going to a 15 is not much of an improvement.
    15 / 9.9 = 1.515 -> 52% increase in horsepower, that's pretty substantial.

    But you're right, no more than what the added cost would be, a 15 hp vs a 25 hp wouldn't be too much extra and make that boat a rocket.

  6. #6
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    A 20 or 25hp motor is the ticket, also go with the 4 stroke, quiet and burns hardly any gas.

  7. #7
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    What size motor is currently on the boat? If you can, move your fuel tank towards the center or front of the boat.
    Likes Rink LIKED above post

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    7mph sounds ridiculous slow for 9.9..Maybe check RPMs and get prop to maximize..Also be sure you got proper shaft length on motor/transom...Long shaft motor on long transom 20" short shaft motor on 15"transom. if its crossed big performance problems...Gota agree if ya gota buy 20_30hp should be great.. 2 or 4 stroke

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    Quote Originally Posted by cva34 View Post
    7mph sounds ridiculous slow for 9.9..Maybe check RPMs and get prop to maximize..Also be sure you got proper shaft length on motor/transom...Long shaft motor on long transom 20" short shaft motor on 15"transom. if its crossed big performance problems...Gota agree if ya gota buy 20_30hp should be great.. 2 or 4 stroke
    Yeah I have to agree here. A 9.9 should push you faster than that. What make and year model is the 9.9? I had a 1982 15hp Evinrude that did about the same on my 1648 and was like it was running on one cylinder or something. After a little troubleshooting, I discovered the powerpack was bad. The internals of these electronics sometimes have high speed and low speed sides and the high speed was out on mine. Bought a used powerpack off ebay for $30 and the motor went from 7-8 mph and 3500 rpms to about 19 mph and up to 6000 or so rpms.

    I'd check the prop first to make sure its not like a 13 pitch or something. 9 or 10 is pretty standard for that size motor. Then may want to check the motor for compression and spark integrity. Best option though would be maybe find a buddy who has a similar sized motor that runs well and see if you can try it on your boat.

    In the event you do get a new motor, I think 25hp is the perfect match for a 1448. It's probably what the boat is rated for and makes for a good economical motor to operate and has plenty of power for the load you can fit into that size of boat.

  10. #10
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    One thing to look at. IF you do have a 9.9hp motor (not really sure at this point) check and see if it is a High Thrust motor.

    I just had this conversation with a guy last night. He was asking me how slow I can get my 9.9 kicker motor to troll. I told him .8mph. He has a much bigger and heavier boat than mine and he can only get down to 1.4. The thing is, anytime someone puts another motor on the back of a boat to use for trolling, they call it a "kicker motor". The truth is, there is a HUGE difference between a standard 9.9hp motor and a 9.9 high thrust or truly designed "Kicker motor".

    As an example, Mercury makes a regular 9.9hp motor. They also produce a 9.9 Kicker motor. The gearing in these two motors is totally different as is the prop. The same is true for Yamaha (although they call theirs a 9.9HT or High Thrust). The gearing is totally different as is the prop. On my boat, the maximum speed I can get out of my 9.9HT is 5mph. If however I had a regular 9.9 motor, I suspect to be up in the 12mph range. And that is on an 18foot deep v
    I have OCD "Obsessive Crappie Disorder"
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