Is mounting motor like this OK ?

Moody Blue

Captain
Joined
May 24, 2004
Messages
3,136
I have a 1993 40HP mariner OB that has been fitted to a 14ft fiberglass whaler style boat. In order to align the cavitation plate with the hull bottom, the motor is sitting up off the top of the transon by about 1 1/4". The motor of course is bolted thru the transom at 4 spots but I am concerned that the bolt holes thru the transom are taking all of the shear load. Should a spacer black be installed between the top of transom and motor bracket?
 

dajohnson53

Lieutenant Commander
Joined
Apr 28, 2004
Messages
1,627
Re: Is mounting motor like this OK ?

I have no idea if it's correct, but I've definitely seen motors mounted like yours with a block taking up the space. I've also seen a lot of motors mounted with the space without a block.
 
D

DJ

Guest
Re: Is mounting motor like this OK ?

Don't worry about it. The four bolts are taking the vertical as well as the lateral load.
 

Chris1956

Supreme Mariner
Joined
Mar 25, 2004
Messages
27,036
Re: Is mounting motor like this OK ?

RodC, My speed boat (150HP Merc, 16' Avenger) has the motor mounted 1-1/4 above the transom. I used a 2X2 pressure treated pine, ripped to 1-1/4 for the block. The thing I would worry about is the transom bolts ripping out, if they are too close to the top of the transom. Id not, you are likely OK. I am considering installing a manual jack plate so I can lift the engine more, aince I am afraid to install a taller block. The Anti-ventilation plate is only about 1/2" above the bottom of the boat.
 

quantumleap

Master Chief Petty Officer
Joined
Feb 16, 2004
Messages
813
Re: Is mounting motor like this OK ?

My 125hp is mounted like you describe with no block. Larger stainless backing washers were added and it is fine. I contemplated using plates such as these http://www.cook-mfg.com/accessories.html but decided not to. I've seen many motors mounted in that manner so I don't believe it's a problem. Even with the top of the mount hooked over the transom, the front edge of the hook doesn't always touch the transom anyway. Don't sweat it.
 

Moody Blue

Captain
Joined
May 24, 2004
Messages
3,136
Re: Is mounting motor like this OK ?

Thanks everyone for the feedback. As suggested I am going to leave well enough alone and enjoy the ride. There is a 1/4" aluminum plate on the inside of the transom about 16" wide x 14" high. I guess that should be more than sufficient.
 
Top