Transom Bolt Washers

[WaterZebra]

Merc has published a highly technical installation manual for their new V8 models. The days of a 1 page diagram and a few sentences are gone. They have even gone to detail that you should "test" your transom by torquing the kit bolts and washers to see if there is any "squish" in the transom construction. If any cracking or "squish" is encountered, they recommend using larger diameter washers to distribute the bolt tension loads. Even straps or plates are mentioned. My question is this....I have lots of room in the lower transom cavity for larger washers and "squish" is not a problem. 2.5 inch DIA? Even 3 inch DIA? Opinions?......

[mrichartz]

What size motor are you hanging V8.
What are you hanging it on. How are you going to use the the boat and where (ruff water, a lake etc)
I would say the bigger the better. If you have the room and its not a huge expensive that your wasting money.
I would put a plate. The more you distribute the weight and force from the motor the better it will be all around..
Ive always installed plates in my boats and its just has a couple little v6s . Actually have plates top and bottom and rods on the upper to the stringers.... Some might say overkill but solid as rock

[FUJIMO]

...bigger the better is right...then after the first seatrial...check tightness with a helper. never turn the bolt, hold the bolt stationary with a helper while the other person tightens the nut. ruins the sealant otherwise. same procedure goes for when you initially install the freshly caulked bolts/nuts...

[Whaaaaat]

Bigger is better, but needs to be thick enough accordingly or it will deform negate its diameter. I rig everything with extra thick washers, I've seen too many wrinkled funnel shaped hardware store fender washers. 1/4 inch aluminum is too thin in my opinion. 3/8 minimum. Mcmaster Carr has a good selection of oversize and extra thick washers. I also only use fine thread bolts for engine or bracket mounting far superior clamping load. Double nuts.

[FUJIMO]

...what whaaaaat said...

[FUJIMO]

...also recommend the fine thread nuts & bolts. i also use fine thread brass nyloc locknuts. they never gall the stainless bolts & lock up. tef-gel is your friend...

[FUJIMO]

[FUJIMO]

[z1rider]

3/8, 3x3" aluminum angle. Trying to nurse that old transom.

[mrichartz]

Eh move to freshwater...lol
my polished stainless steel bolts look the same as the day they were put in....spots/stains from hard water on the other hand what a f,,, pita
But yea x2-3-4 for the tef-gel im in fresh water and still use it never know..

[WaterZebra]

Bigger is better, but needs to be thick enough accordingly or it will deform negate its diameter. I rig everything with extra thick washers, I've seen too many wrinkled funnel shaped hardware store fender washers. 1/4 inch aluminum is too thin in my opinion. 3/8 minimum. Mcmaster Carr has a good selection of oversize and extra thick washers. I also only use fine thread bolts for engine or bracket mounting far superior clamping load. Double nuts.

Thanks everyone for the input. Haven't used Tuff Gel before. Ordered some today. I think I'm going to go with a 3/8 aluminum strap on the lowers. Bolt pattern appears to be BIA standard. Will have to make my own strap though. A lot of listings online for the upper bolt set but nothing for the lowers. The BIA pattern looked small to me but it is what it is I suppose. I find it hard to believe that Merc would use the BIA pattern on their new V12?

[LakeFever]

I’m going to use 1/2” aluminum. Tef-gel looks very similar if not the same as super lube

[FUJIMO]

I’m going to use 1/2” aluminum. Tef-gel looks very similar if not the same as super lube

...super lube is not the same as tef-gel...

[mrichartz]

Had it wrong nit that anybodys looking but..
Actually the stainless steel rods on mine go to middle bolts on the setback bracket.. (lazer was from the top)
My motors aren't bolted to the transom its brackets ..
Point is the metal underneath used stainless steel still as hell dont remember what but when went to cut or bend it forget it..




Still the bigger stronger the better..

I had a point to this but lost my train of thought.. lol
When it comes back.. if..

And tef-gel has other ingredients keeps the hardware from galling other lubes or silicones dont.

[Whaaaaat]

Upper bolts are most critical. There under the most stresses. They spec 2 uppers now? I try to always put 2 on anything that will take a beating.