Boat performance

[ckone0814]

2006 Century 18' dc with Yami 115 4s. Pretty heavy boat with prob not enough motor but it is what it is. Want to get the most out of it we can till we upsize in a few years. As far as I know boat and motor are stock and no tabs of any kind. Had it out three times this spring so far and it takes awhile to get a head of steam and get on plane, no holeshot to speak of, speedo shows 30 mph with 2 people, 27 with four.

Before I start to ask all kinds of questions about props, pitch, engine setup, tabs, etc what data do i need to gather and how? Is there a good website or something? Thanks in advance.

 

[rrhodes]

Re: Boat performance

What is your current prop and what is your RPMs at WOT (Wide Open Throttle)

 

[Action]

Re: Boat performance

2006 Century 18' dc with Yami 115 4s. Pretty heavy boat with prob not enough motor but it is what it is. Want to get the most out of it we can till we upsize in a few years. As far as I know boat and motor are stock and no tabs of any kind. Had it out three times this spring so far and it takes awhile to get a head of steam and get on plane, no holeshot to speak of, speedo shows 30 mph with 2 people, 27 with four.

That does seem pretty slow for that setup, I'd imagine it probably has the incorrect prop on it....I have seen trim tabs on that style of boat before and might be a good idea for getting up on a plane more quickly.....What's the max hp rating on that? 150hp? Is it the digital speedo from Yamaha?

 

[Silvertip]

Re: Boat performance

Every engine manufacturer specifies a maximum wide open throttle rpm which for your engine is 5000 - 6000 rpm with an average load. Ideally you want to "observe" closer to 6000 rpm for best performance. So you need to make some wide open throttle runs with what you consider an average load. Note the speed and rpm at WOT. Then check the prop to see what diameter and pitch is and post your results in the PROP FORUM. If your engine cannot reach 6000 rpm it is over propped (too much pitch) and is lugging which is bad for the engine. If the engine easily exceeds 6000 rpm it is under propped (too little pitch) which is also bad for the engine. Happiness is a prop that get the engine close to 6000 rpm. Speed will be whatever that prop provides so don't get the idea you can simply slap a prop on and go faster. The engine has only so much power and it can only twist a certain prop with a certain load.

 

[ckone0814]

Re: Boat performance

Yes the max hp is 150.

No on the digital gauges, I have analog.

Yamaha performance bulletin from 2005 has 38.3 mph (no way) at 6100 rpm, 4.53 secs to plane (again, no way) with two people. Prop was the eom 13 x 17 x 3 blade black steel.

Prop on it now is the same as above. I need to get the rpms at wot.

Thanks all.

 

[Action]

Re: Boat performance

Yes the max hp is 150.
No on the digital gauges, I have analog.
Yamaha performance bulletin from 2005 has 38.3 mph (no way) at 6100 rpm, 4.53 secs to plane (again, no way) with two people. Prop was the eom 13 x 17 x 3 blade black steel.
Prop on it now is the same as above. I need to get the rpms at wot.
Thanks all.

Hrm, well one thing, you might want to find out what your speed is via GPS, because that's how all the water tests are recorded, your speedo may be off. That being said, I have the same prop on my 90hp and it is very good for the 17ft I have, but i know your boat is much heavier. Even still, the Four stroke 115 yamaha is a very torquey motor, you could go to a 19P but your hole shot is going to be even worse then it is...What are your rpms now?

 

[ckone0814]

Re: Boat performance

Hrm, well one thing, you might want to find out what your speed is via GPS, What are your rpms now?

I'll finish installing the gps this week so I'll know a better mph this weekend at the latest. rpms I don't know yet - didn't take notice - have to wait for the next day out. FWIW our loaded weight probably was around 3600 lbs.

We won't be doing anything more than fishing and cruising with an occasional tube ride. I'm just looking to make sure i'm getting the best bang i can.