Yamaha 20 hp 4 stroke

M

Malkolee

Recruit
Joined
Aug 28, 2009
Messages
2
I recently purchased a polarcraft 16.5' aluminum fishing boat with a 20hp Yamaha 4 stroke. This is a bass style boat a little over over 900 lbs. dry weight. The 20hp cannot push this boat past about 10mph. My older boat, which was about 200 lbs lighter, with a 9.9 2 stroke could outrun this by a ton. Is this the best I can expect from this motor? Are there better props or hp boosters that can help? I would appreciate any comments.
Thank You
Lee M
 
S

swordfish25

Petty Officer 2nd Class
Joined
Mar 18, 2009
Messages
117
Re: Yamaha 20 hp 4 stroke

It should run faster then that. Is it running on 2 cylinders, or just 1?
 
S

steelespike

Supreme Mariner
Joined
Apr 26, 2002
Messages
19,069
Re: Yamaha 20 hp 4 stroke

You may need to move this to the prop section.As suggested
check it is runnung on all cylinders and that the throttle opens all the way.
You'll need a tinytach (easy install about $40)and a gps to solve your problem right.We'll need your present prop size,your present max rpm and speed.
 
M

Malkolee

Recruit
Joined
Aug 28, 2009
Messages
2
Re: Yamaha 20 hp 4 stroke

steelespike said:
You may need to move this to the prop section.As suggested
check it is runnung on all cylinders and that the throttle opens all the way.
You'll need a tinytach (easy install about $40)and a gps to solve your problem right.We'll need your present prop size,your present max rpm and speed.
Click to expand...

I can't find anything that tells me the prop size but I am going to talk to the tech who is setting the boat up and put your questions to him. The boat does have a tach and when it is opened up it goes to the top which as I recall is about 7000 rpm. They are telling me that this is as fast as the motor can go. Even if it is pushing around 1400 lbs does that sound right to you?
 
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