View Full Version : 40hp on a 42m tinnie

dave kilpshe
12-26-2005, 06:37 AM

currently i have a 25hp enigine on my 4.2m tinnie, it isnt a dodgy built boat, and is generally quite strong, however it says on the boat, that a max of 30hp can be installed onto it....

we have access to many sized motors, and 30hp isnt what we are after, we are looking to put in a 40hp, which weights about 100kg, a 30hp weights 60kg

what factors must i consider before installing i install the motor? would structual issues of the boat need to be considered?

obviously with the weight, the bow is gonna lift, but counter weights can be used ( larger fuel tank, placed at the front) and obviously it will sit lower in the water aswell

whats the issues regarding this engine upgrade?


12-26-2005, 01:03 PM
"The primary issues are safety & stability - Exceeding the maximum rated hp or capacity is a bad idea.

Here is a link to USCG guidlines for backyard boat builders to calculate safe HP and load ratings.

http://files.dnr.state.mn.us/education_safety/safety/boatwater/backyardboatbuild ers.pdf ("")

Quoting from the guidelines... "Overloading and overpowering cause many boating accidents, particularly capsizings, which is why these capacities are important to the safe operation of your boat."

Stay safe