Loaded boat....full throttle - low revs

[ggmu89]

Hi All,

I am just a beginner currently experiencing my first summer as a boat owner. I own a 13.6ft fibre boat with a Tohatsu 40tldi outboard motor.

On my own or with two people (myself and my wife) the boat planes easily and it can go quite fast....However last weekend another couple joined and we decided to roam aorund a bit...However even at full throttle the outboard couldn't rev more than 3000 and the speed was quite slow.

I mean I fully understand that with the increase in load that the speed goes down however I am bit unsure about the revvs thing. Does it have to do simply to the load the boat can take? Is it related to a motor issue? or is it related to the propeller?

I know this might sound stupid to most of you but please bear in mind that I am a total novice to boating and looking forward to acquire some knowledge from the wisdom of the many experienced boaters in here.

Thanks in advance for your kind insight.

Keith

 

[David Young]

Many years ago I had a boat that did what your boat does. Had good top speed with 2 people but had no speed with 4 people. My motor was worn out . Check your compression. You can rent a gauge from most auto parts stores for just a deposit, you get back every cent when you return it

 

[Sea Rider]

Welcome to Iboats,

What's the boat's max HP transom rated for and for how many passengers to start with. Assume is a relatively new OB, right ?

Happy Boating

 

[180shabah]

lots of variables here. If everything is fine with just two aboard, then you add an additional 200-400 lbs of people and gear, performance will suffer. How much, is the real question. You have a relatively small boat and 40hp, changes will be much more pronounced than on a 20 footer with 200hp. You probably need to run a lower pitched prop if you carry additional weight.

 

[roscoe]

Problem likely has to do with revs, and propeller.

What are the revs when you are in the boat alone, at full throttle ( wide open throttle - WOT ) ?


Your motor is made to run 5150 - 5850 rpm at WOT.
You need to purchase a prop that will allow the motor to reach these rpm.
5500-5800 rpm would be best.

Then, when you add the additional passengers, the motor will have the power it needs.