Boat size vs motor size

[Zikka]

Hi All,<br /><br />I'm brand new to boating so I'm pretty green. I have a 18' 1975 Doral Runabout (around 2500 lbs or so) with a Mercury Thunderbolt 850. It runs great but....<br /><br />I'm wondering if the 850 is a little under power for the size of the boat. It takes to boat around 5 mins to get up to it's maximum speed (34km / h or 20 mph).<br /><br />My questions are; <br /><br />is this the best that this boat/motor combo will do?<br /><br />will a tune up / service improve the power of the motor?<br /><br />Is there anything that can be done to improve power (beside buying a larger motor)? Maybe a different prop?<br /><br />Thanks for your comments.

 

[Jack Shellac]

Re: Boat size vs motor size

What is the maximum horsepower listed on the plate in the boat? 20 MPH dosn't sound right for this combination. Seems like you should be getting more speed from it. How many RPM does the motor turn at full throttle?

 

[Specks n Reds]

Re: Boat size vs motor size

 

[Zikka]

Re: Boat size vs motor size

thanks for you replies. As I said, I am new to all of this and don't really know how heavy the boat is. I'll check the plate on it next time i'm at the cottage. If it helps, the boat looks like this http://www.cronkwright.com/doral_boat.htm <br /><br />Cheers.

 

[xxlondonxx]

Re: Boat size vs motor size

Perhaps the control box is not opening the throttle enough to open the motor up to top power. How is the motor running generally?

 

[JerseyJim]

Re: Boat size vs motor size

you should be in the lower 30s minimum with that kind of horsepower - do you have a tach? if so what RPM is it listing at WOT?

 

[DJ]

Re: Boat size vs motor size

XX,<br /><br />Without knowing what your wide open throttle rpm is, it's a bit difficult to judge.<br /><br />If your wide open (WOT) rpm is 4500 or less, you are probably overpropped or the engine may need some attention.