Avoiding lag bolts on engine mounts?

[tpenfield]

Re: Avoiding lag bolts on engine mounts?

My current and previous boat did not have lag bolts for the engine mounts. They were thru-bolted using special right angle brackets that were also thru-bolted to the stringers. A more complicated mounting system, but it is much stronger and avoids the rot-out issues of lag bolt mounting.

So, you options are to get specialized hardware, or fabricate a thru-bolt mount as show in a couple of the previous posts. You will want to make sure that any fabricated mount is beefy enough to handle the stresses that the engine will exert on it.

FWIW - I am not a fan of lag bolt mounting . . . you tend not to see that technique in offshore boats, which are designed to take a beating. So, there must be some method to that madness.

 

[RacinRob]

Re: Avoiding lag bolts on engine mounts?

The only problem with thru bolting the side bolts is that if there is a problem I need to tear up the floor to remove engine etc. I did think of that though.

Thinking out loud here. Instead of the wood mount glassed in to the stringer, how about a thru bolted aluminum block to the stringer? Then bolt the engine mounts via tapped holes in the block. Hmmm

Tpenfield,
I've been on a lot of off shore boats and really like the Formulas. The fastest I've been was 135 GPS in an Eliminator Daytona race boat. The Skater I took a ride in was capable of 180, but we had no room to make that run and stopped at 120. I looked at a little older SS a few years ago but did not pull the trigger. My sister has a 382 Fastec. 1500 HP. Hauls ***. I was going to build the new engines for it but backed out because of her being family just in case something did not work out.

 

[TJS]

Re: Avoiding lag bolts on engine mounts?

To the OP. I posted my idea about not using lags. I think lags are very unsafe. It does not matter that "well if the factory uses them they must be right". Not true at all. You can see my idea here.

http://forums.iboats.com/boat-resto...pair/motor-mount-fabrication-long-621845.html

 

[RacinRob]

Re: Avoiding lag bolts on engine mounts?

I liked outside the box thinking. You can never over engineer engine stability. When I'm doing 150 mph on the track, or 50 on my ski boat I want the same security. There is more stress in a boat hitting wake after wake than there is in any car application. My 750 hp in the race car is held in by basically 2 bolts. My engine/trans has 16 bolts holding it in the boat. There must be a reason for that. I see a lot of torsional stress that can happen in this style of boat. Some good ideas coming through, thanks.