Avoiding lag bolts on engine mounts?

I have had a couple suggestions on another thread here, but it was buried in another topic. How can I avoid using lag bolts on my new motor mounts? 3/8" lag bolts presently. I'm thinking an insert of some type. WOG recommended epoxying a nut in the mount. Any thoughts on that? Maybe a wing nut upside down with the "wings" staked? Any and all suggestions will be greatly appreciated. Thanks in advance for the help. Also thanks for the other couple suggestions before.

Re: Avoiding lag bolts on engine mounts?

I am assuming that it is an inboard engine. How many bolts on each side? Got any pics of the mount? That would help.

Re: Avoiding lag bolts on engine mounts?

It is a direct drive ski boat. Each side has three in the front on the engine and four on the transmission mount. The motor mount has two facing down and one towards the stringer/mount. The trans has two down and two towards the mount. Pics attached. First two are the trans. Second are the engine.

Re: Avoiding lag bolts on engine mounts?

RacinRob said:

I have had a couple suggestions on another thread here, but it was buried in another topic. How can I avoid using lag bolts on my new motor mounts? 3/8" lag bolts presently. I'm thinking an insert of some type. WOG recommended epoxying a nut in the mount. Any thoughts on that? Maybe a wing nut upside down with the "wings" staked? Any and all suggestions will be greatly appreciated. Thanks in advance for the help. Also thanks for the other couple suggestions before.

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Ayuh,..... Why,..?? 99% of the mounts out there use lags, 'n have for Ages,....

Yer plan will complicate motor/ driveline alignment in many ways, with no real pay-back,...

Re: Avoiding lag bolts on engine mounts?

Trying to limit water intrusion that will in turn cause rot again. That is the payback. How can it complicate driveshaft alignment when it has multiple ways of adjustment? Each mount attached to the engine adjusts up, down, left and right. Trans and engine mount both adjust like that.

Re: Avoiding lag bolts on engine mounts?

RacinRob said:

Trying to limit water intrusion that will in turn cause rot again. That is the payback. How can it complicate driveshaft alignment when it has multiple ways of adjustment? Each mount attached to the engine adjusts up, down, left and right. Trans and engine mount both adjust like that.

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What makes ya think yer wing-nut is gonna be anymore "water-tight",..??

Anywhere there's a transition from 1 material to another is a water seepage point,...

Metal to wood, wood to epoxy,...
Put in a glass bed, 'n pre-drill for the lags,...
Freezin' temps, 'n moisture will eventually crack it too,...

Keepin' the bilge dry is the Best insurance against wood rot,...

Re: Avoiding lag bolts on engine mounts?

Explain the glass bed please.
Not much freezing where I live. 10-20 days a year in the 20's. I water ski year round almost.
Its hard to keep the bilge dry in a ski boat. The engine mounts are about 1.5" below the floor level and people in and out of the boat all day lets water run right into the mount area. No way to avoid it getting wet. The original set up has glass over wood stringers with the engine mount encased in the same layup. The lags go thru the metal engine mount into the fiberglassed engine mount. That is where the water gets around and under where the metal mount sits on top of the fiberglass and seeps around the lags like on every boat designed this way. If I use something like a nutsert glassed and epoxied into the wood mount there is no way for water to get to the wood. I was just looking for alternate ways of achieving this. Here is a picture of a nutsert insert.

Re: Avoiding lag bolts on engine mounts?

Just my 2?...
Really more of a thinking point...
Wouldn't using a liberal amount of 5200 between the mounts and the mounting points, plus the threads and holes where the lags go pretty much seal up the works...?
Considering two things, the age of the boat and how long it lasted as originally designed, plus now it will all be better than new...with new wood, glass and hardware...

Re: Avoiding lag bolts on engine mounts?

I've been thinking on that line GT. just fill with sealer (5200) then screw in the bolts. Your right about lasting a long time already. 20 plus years. I'm sure it had no sealer originally. Maybe I'm just over engineering and thinking.

Re: Avoiding lag bolts on engine mounts?

Lag bolts were OEM for a reason, build your boat back OEM.

Lag bolts didn't rot your wood, owner neglect rotted the wood. As Bond-O said"Keep your bilge dry" and you won't ave anything to worry about.

You can improve on OEM a little. Line everything up and install the lags, Then remove the lags one at a time and squirt the 5200 into the hole and reinstall until all have been sealed.

Re: Avoiding lag bolts on engine mounts?

jigngrub said:

Lag bolts were OEM for a reason, build your boat back OEM.

Lag bolts didn't rot your wood, owner neglect rotted the wood. As Bond-O said"Keep your bilge dry" and you won't ave anything to worry about.
.

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Lag bolts are a cheap, easy way to mass produce a product with no fore thought to the longevity of a product. Actually the factory installed tow pylon ruined the stringers. The 6 holes drilled thru the transom on each side to install the pylon were rotted in that area. The water migrated rearward from there. One side is a lot worse than the other. The rot on the other side is starting forward and working its way back just like the real bad side. Also, the lag bolted mount area is a lot worse than lower in that same area. Like I said before, the water in the bilge gets pumped out all day long. I probably take on 50 gallons a day with all the in and out of the water activity, water fights in the summer, etc. It gets pumped out, but as it enters it drains over all the unprotected thru bolting and motor mount hardware that was never sealed from the factory. When I get done using the boat I let it dry out and then cover it. It never sits uncovered in the rain, and I leave the drain plug out just in case. The last couple years I only have used it maybe twice a month, but the previous 13 I owned it it was in the water 2-3 days a week from April to Sept, and 2 days a month the rest of the year. It gets used. It does not sit around and get used a 6-12 times a year like most people use their ski boats. It's not a fishing boat that doesn't see much water intrusion on a typical day out. It gets. Wet every day it is on the water. With all that activity I am just trying to make it as watertight as possible. I keep things a long time. My daily driver Toyota truck has 650,000 miles on it with one engine change at 568k. This should show that dont neglet my things, I use them. I just want this boat to last and not worry about it down the road. And I want it sound when I finally sell it.

Re: Avoiding lag bolts on engine mounts?

Make your mounts so you can access under them.




Then: sit the motor down into its position you want, mark the place for the holes. Remove the engine.

Drill over size holes in the mounts in the center of those marks.

Fill the large holes with epoxy and your favorite thickener (short strands of glass cloth mixed in)

After it cures, drill smaller holes to the diameter of your engine mount bolts in the center of the epoxy plug.


Mount your motor using locking nuts and large fender washers or perhaps some stainless backing plate to act as a thick washer.

Water cant get in the wood. Your done.


This is the second time open mounts have been proposed to you. Never saw a response as to what the issue is?


Chris

Re: Avoiding lag bolts on engine mounts?

PS. Speaking of fishing boats. This is what I fish from and this is one fish I have caught from it.

Re: Avoiding lag bolts on engine mounts?

Chconger, sorry to not respond to this before. It may work with some modification. My mounts bolt in two different directions down and also out. I could add a plate to the front of the box to thru bolt towards the stringer too. I would need to leave enough room down low to get a hand in to get nuts on to the bolts. I would need two more for the transmission too. Just wanted options, this looks like a good one.

Thanks, Rob

Re: Avoiding lag bolts on engine mounts?

RacinRob said:

Lag bolts are a cheap, easy way to mass produce a product with no fore thought to the longevity of a product.

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No, hex head lags and lag studs are the best/strongest fastener/anchor for this application. Try using something else and you'll find out why lag bolts were OEM.

Re: Avoiding lag bolts on engine mounts?

RacinRob said:

Explain the glass bed please.
Not much freezing where I live. 10-20 days a year in the 20's. I water ski year round almost.
Its hard to keep the bilge dry in a ski boat. The engine mounts are about 1.5" below the floor level and people in and out of the boat all day lets water run right into the mount area. No way to avoid it getting wet. The original set up has glass over wood stringers with the engine mount encased in the same layup. The lags go thru the metal engine mount into the fiberglassed engine mount. That is where the water gets around and under where the metal mount sits on top of the fiberglass and seeps around the lags like on every boat designed this way. If I use something like a nutsert glassed and epoxied into the wood mount there is no way for water to get to the wood. I was just looking for alternate ways of achieving this. Here is a picture of a nutsert insert.

Click to expand...

Ayuh,... Like chconger says, ya drill huge over-sized holes, 'n fill 'em with fiberglass, 'n resin, then redrill for the lags,....

Re: Avoiding lag bolts on engine mounts?

Another tack to take is to address the wood used as opposed to the fasteners. There are some amazing species to choose from.



My original mounts were enclosed, found them filled with water, and in perfect condition after 25 years...



White oak 'n lag bolts;

Re: Avoiding lag bolts on engine mounts?

Thanks. I'm going with lags and doing what I can with them to limit the water issue with glass and resin holes.

Thanks all, Rob

Re: Avoiding lag bolts on engine mounts?

You will be fine with well bedded lag screws.
FYI for others considering options. ... the method that "chconger" suggested would work fine for an I/O, however I would not recommend it for an inboard. One needs to keep in mind that with an I/O the outdrive is hung off the transom, so all the forward thrust of the propeller is transfered though the outdrive and right to the transom. The motor mounts on on I/O don't do a whole lot more than just hold the engine in place. -- On an inboard, all the thrust of the propeller is transfered to the prop shaft and right up to the engine and to the motor mounts. In reality the motor mounts on an inboard are 'pulling' the boat forward though the water. They have a much tougher job than on an I/O

Re: Avoiding lag bolts on engine mounts?

Your side bolts could be through drilled and filled and use stainless bolts and nuts. I would over size drill it and fill and redrill proper size though and even then still use 5200. Just a thought that would provide a little more strength than just lags would for the side mounts. All racing boats are done this way. They don't even use top mounts just the side mounts drilled through.