15'2 Coastal

[Coastal]

Just finished rebuilding my 1994 15'2" Coastal. I put a new floor in it, fixxed every nick and inperfection on the bottom, painted insided and out w/parker duck boat paint. Upgraded from a Mercury 40, to a Mercury 60, fresh rebuild, 30 over, w/16p Vengence Prop. With the Merc 40 that was on the boat I could get right at 39 mph. I was expecting much better numbers with the 2 stroke 60. I gps'd the boat the other day and got 42-43 mph. Help, any ideas to get a few more mph.. I weigh about 280, the boat will not lift as it is, I do have the battery in the front thinking about mounting it in the back.

- Cleaver/Chopper?
- Jackplate, 4 or 6 inch setback

[88workcar]

For starters move the batt to the back, and use a little battery, garden tractor battery is best. The from the looks of the pictures your motor is way too low. The less setback the better. See if you can lift it with no setback. As you lift you will need more prop.

[Jackson]

Good looking Boat

[Coastal]

Jackson, thanks. 88, the transom has actually been built up. It was much lower. The cavitation plate actually is maybe 1 inch above the bottom of the pad. Thanks for the input, I have always thought that a setback would help, your saying try not too. Thanks.

[milkdud]

Looks like your adding close to 5 mph to that rig by going up 20 hp.

On the same boat and set up it takes big HP increases to get lots of MPH in the upper range.

Friction adds up hard on the top end. Im not sure about your motors but Mercury and other manufacturers for that matter sometimes use the same cubic inch block for several hp motors. So going from a 40hp motor to a 60 can be a less than satisfying move.

Playing with set up and props will help.

Nice boat!

Conrad

[milkdud]

Just as I thought.

http://www.defender.com/inflatables/...2/merc_75.html


The 40, 50, and 60 hp 3 cyl 2 strokes are ALL 966 cc motors.


So I say your doing well for what you have.

To put it into perspective the 75hp OPTI has 1526 cc. Rated only 15 more HP than your motor but has more that 50% MORE CUBES. And more weight

Now that 75 opti is gonna produce good hp with that much displacement. Kinda a sleeper. Yours is probably using all the tricks in the book to be putting out 60 hp.

Conrad

[mad yama]

I have the same boat with a 40 yamaha that run 60 62 allday long need to take as much as u can out the ft and i have light boat

[milkdud]

I have the same boat with a 40 yamaha that run 60 62 allday long need to take as much as u can out the ft and i have light boat

That sounds amazingly fast. Are you using a GPS or what for these readings?

Ive been amazed before at how fast some boats can go, but 62 mph out of this style boat and only 40 hp seems a bit faster than reality.

Conrad

[Coastal]

My lil brother has a 15' Fast Craft w/60 Merc, runs in the low 50's. It's a light boat. I've got a heavy new floor.

[milkdud]

My lil brother

Costal, If your little brother is lighter than you and his boat is lighter to boot then I could easily see more speed out of his boat.

It sounds like you got your motor up where it should be, but I'm guessing your total weight is higher then your brothers.

Good luck and nice boat
Conrad