engine size

I have a 16 ft thundercraft tri-hull open bow...top engine rate is 115hp..5-6 passenger...boat is approx 1000lbs?...i dont use it for pulling skiers or tubers or racing,,,just crusing on the Ohio river and lakes...is a 70 hp merc big enuff engine for this boat...I dont need speed but I would like a enuff speed and power to get out of the way of the barges and cigaret boats..:0)....thanks..

Re: engine size

It should be marginal if lightly loaded. I would rather see you go with at least an 85 V4 with the 115 hp preferred. You can always go slower and take less people but not the reverse.<br /><br />If you wat to get out of the way of a Cigarette you're goin to need a LOT more boat.

Re: engine size

I'll put it to you this way. My tri-hull center console is 16.5 feet, rated for 145 hp, and has 125 hp. It certainly gets it done, but I am on a passive hopeful search to come across a 150 horse. If you pack several people on, you'll really wish you had the 115. <br /><br />Tri-hulls need more power than a v hull of the same size, there is more wetted surface, which robs power. My rig isn't quite as happy if I stack four carcasses in it, but it does come on plane and cruise decently. It just takes a bit longer to get up on plane. <br /><br />A 70 horse may not get you on plane when fully loaded with several people, then you'll be cruising around with the bow in the sky or at displacement speeds. Trim tabs can help, but if you are going to spend the loot, apply the loot towards a larger engine. It won't work as hard, and you don't have to run it at full throttle all the time. A larger engine running at part throttle will get better economy and last longer than a smaller engine running wide open. Either way you go, good luck...

Re: engine size

You seldom here someone say "boy I wish I had less horsepower".

Re: engine size

Go for the bigger motor less fuel and less stress.<br />mine is 16 ft had 80 hp changed to 135hp used to cruise at 25 mph now 35 but wish i went to 150 hp<br />bigger the better . but dont go crazy with the speed.

Re: engine size

Sounds like the cost of a 115hp is over the budget line. We sell a lot of our Smart Tabs in Europe simply because the gas cost is very high and therefor the motors are smaller. <br /><br />Hull efficiency is equaly important when it comes to performance. If fact excessive HP (weight)can reduce efficiency in terms of boat speed and fuel consumption.<br /><br />Trim Tabs improve performance and efficiency simply because they adjust the hull design to compensate for the changing speeds and conditions.

Re: engine size

A 70 is at best marginal! An 90 or 115 would be the only way to go!

Re: engine size

I use a general rule of thumb that 70% of the rated power is minimum for satisfactory general use.<br /><br />That puts the 70 as too small and an 85 as just above minimums.<br /><br />There are a lot of good, reliable 90s and 115s out there. . . new or used.<br /><br />Good luck.