motor mounting height

2

2MADAKAT

Petty Officer 2nd Class

Joined

May 13, 2004

Messages

143

• Aug 19, 2005

• #1

A friend of mine rebuilt the transom on my 1984 Bayliner Capri. While doing so he raised it by<br />3.5". The motor is a 20" Yamaha 115HP and whenever I am in wavy water, the motor acts sputters and loses power.<br />Does anybody know how high the motor should be mounted or how far above the drain hole the aluminum motor mounting plate should be?

 

P

PuddleJumper

Petty Officer 1st Class

Joined

Jun 6, 2005

Messages

314

• Aug 20, 2005

• #2

Re: motor mounting height

Rule of Thumb starting point is the anti=ventilation plate should be 1 inch above bottom of hull. If your motor is now 3 in above you run the risk of losing water pressure and overheating.A jack plate would probably be the simplest fix.

 

L

lark2004

Lieutenant Junior Grade

Joined

Jul 12, 2004

Messages

1,080

• Aug 21, 2005

• #3

Re: motor mounting height

No, the rule of thumb for the starting point is; AV plate should be level with the bottom of the hull.<br /><br />However, a Jackplate will be your easiest way of fixing the big mistake your friend made when he stuffed up the measurements on your transom. Maybe ask this friend to help out with the cost, It was his mistake.

 

AMD Rules

Lieutenant Commander

Joined

Sep 23, 2004

Messages

1,707

• Aug 21, 2005

• #4

Re: motor mounting height

A sawzall should remove 3.5" from that transom pretty quickly. A lot cheaper than a jack plate.

 

B

Braxton

Chief Petty Officer

Joined

Jul 16, 2005

Messages

575

• Aug 21, 2005

• #5

Re: motor mounting height

don't want to sound stupid but was is a jack plate? Just wondering

 

AMD Rules

Lieutenant Commander

Joined

Sep 23, 2004

Messages

1,707

• Aug 21, 2005

• #6

Re: motor mounting height

Transom attachments that allow you to move the motor up/down vertically. Some also include tilt&trim features as well.<br /><br />iBoatsMall Jack Plates

 

B

Braxton

Chief Petty Officer

Joined

Jul 16, 2005

Messages

575

• Aug 21, 2005

• #7

Re: motor mounting height

thanks AMD that is a cool thing,

 

2

2MADAKAT

Petty Officer 2nd Class

Joined

May 13, 2004

Messages

143

• Aug 21, 2005

• #8

Re: motor mounting height

Is the anti-ventilation plate the same thing as the aluminum plate covering my transom through which my motor is bolted to?<br />Do these plates come in different sizes?<br />My drain plug hole is 1/2" above bottom of hull.<br />Total height of drain plug is 2-1/2" from bottom of hull. Plate is 15" wide. Where do I mount the plate?

 

AMD Rules

Lieutenant Commander

Joined

Sep 23, 2004

Messages

1,707

• Aug 21, 2005

• #9

Re: motor mounting height

Have a peek at the image on this site, showing where the AV plate (cavitation plate) should be when looking from the side.<br /><br />Installing an Engine on a Transom.

 

2

2MADAKAT

Petty Officer 2nd Class

Joined

May 13, 2004

Messages

143

• Aug 22, 2005

• #10

Re: motor mounting height

Thanks AMD, now I know what an anti-ventilation plate is and will know what to look for when I check out my engine.

 

U

ufm82

Master Chief Petty Officer

Joined

Jul 29, 2003

Messages

827

• Aug 22, 2005

• #11

Re: motor mounting height

Thank you AMD for posting that link- I've always wanted to reference a site somewhere when people ask me about engine height. <br /><br /> Keep in mind that the measurement there is a good place to start. Some will do better up higher and some will do better down lower but that 1" spec is a great starting point.<br /><br /> Jackplates can change that number by 6" at the touch of your thumb. Very handy on boats that run into shallow water and high-performance boats like bass boats that need the prop deep to get holeshot but want to run shallow to reduce drag. <br /><br />UFM82