Am I that Underpowered???

dhughes214

Petty Officer 2nd Class
Joined
Jul 11, 2009
Messages
122
I hope I am in the right place, I am new to this forum.

I have an Evinrude Lark X 40 HP outboard (not sure what year will post the model number soon, thinking late 60's early 70's), it's on a 1971 16ft Chrysler hull. My buddy owed me 700, and I knew he didn't have and wouldn't have the money so I took the boat instead since the registration was all current. He said the guy he got it from told him it did 25-30 mph with two people in it. The problem: I'm getting 12 mph. It's not even acting like it wants to plane. This boat is a tank, so I'm sure 40hp is underpowered, but 12 mph??? With 4 people we barely made 9 mph. Am I really that underpowered or is it a motor problem?? No tach, only speedometer. Any help greatly appreciated. Oh, the hull's max rated hp is 115.
 

a70eliminator

Captain
Joined
Sep 9, 2007
Messages
3,762
Re: Am I that Underpowered???

My 67 mfg fiberglass 16' does about 30mph with an 80hp, your underpowered for sure but I would think the 40 should at least get you up on plane if it's propped right and in tune.
 

kenmyfam

Supreme Mariner
Joined
Aug 10, 2006
Messages
14,392
Re: Am I that Underpowered???

You should be around 75% of the rated max HP to get a reasonable performance from the hull. So ideally an 85 HP minimum.
40HP may get you on plane if the motor is performing as it should and the boat is loaded and propped correctly.
Do a general health check of the motor to give yourself an indication of it's condition.
Compression, spark, fuel delivery, plug condition and cooling will be good for starters. Post your results and go from there.
Info on the testing can be found in the "Top Secret Files" section at the top of page 1.
 

dhughes214

Petty Officer 2nd Class
Joined
Jul 11, 2009
Messages
122
Re: Am I that Underpowered???

Ok, I just said the heck with it and bought a 115hp evinrude, it's a 1972, the guy started it up for me, sounded good. Thanks for the help though. anybody know where I can get a wiring diagram?
 
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