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View Full Version : Attn: Clamshell motorbox owners-lift shocks


rasmithaz
09-19-2009, 02:55 PM
The upper part of my clamshell engine motorbox (some people call it a cowling) has never stayed open on it's own. I just installed 40 lb. spring lift shocks to replace the 20 lb originals and it still doesn't stay open. Is it designed to stay open or just dampen the opening and closing? I could go to 80 lb shocks but that seems like a lot of overkill to replace 20 lb. original equipment.

gibbons
09-19-2009, 04:07 PM
Sure. And you can get them on eBay for about $25 a set.

Chicago190
09-19-2009, 04:39 PM
Is there a step between 40 and 80 lbs? It should definitely stay open, but I've taken mine off and I don't think its more than 75 lbs.

shepherd
09-19-2009, 04:46 PM
Be careful. When I bought my boat (used) the hinges were torn out of the fiberglass in the bottom half of the box. The dealer blamed it on oversized lift shocks putting too much force on the hinges. Previous owner may have let it slam open a lot too. Lucky for me, the dealer - Mastercraft of Charlotte - had Mastercraft send me a whole new engine box to replace the old damaged one, free of charge. My old engine box makes a nice end table in the man cave now.

I'm not trying to scare you, and I agree that your lift struts should hold the box open, but I suggest you use the smallest capacity shocks that will do the job for you.

JLeuck64
09-19-2009, 05:09 PM
I had a different, but similar, situation to yours. My lift springs hold the entire engine cover up off the floor. The trouble was it was just a little too low for my liking and it would sometimes let the cover fall down. What I did was to move the lower mounts back some. They still have enough room to close completely without binding and the old holes disappeared in the carpet so you can't really tell where they used to be mounted any way. Maybe you could experiment with moving the mounting points on your lift springs also...

rasmithaz
09-19-2009, 06:20 PM
this is a two piece box, it is just the upper piece that doesn't stay up. The entire two piece unit stays up with the lower shocks. It's those little 7.5 inch spring shocks that lift the upper portion off the lower portion that are not doing the job I think they should be doing.

TMCNo1
09-19-2009, 07:11 PM
Check with these people about their gas springs, http://www.marksrv.com/contact.htm and Attwood, http://www.attwoodmarine.com/store/product/gas-springs0, also makes them and are sold through most RV dealers.

You should have a stick on tag and or part/model numbers printed on the original shocks as/for reference.

JLeuck64
09-20-2009, 06:48 PM
this is a two piece box, it is just the upper piece that doesn't stay up. The entire two piece unit stays up with the lower shocks. It's those little 7.5 inch spring shocks that lift the upper portion off the lower portion that are not doing the job I think they should be doing.

So... could you reposition those little guys at all? If you can it will change the balance point of the top cover which should make it easier for the assist springs to hold it open.

Thrall
09-21-2009, 10:11 AM
You shouldn't need heavy shocks to lift just the top section. Likely, the mounts have been moved to where it doesn't open up to work right. I'd think 2 - 20lb shocks would be sufficient. Don't just keep upping the shock weight, or you may get too much pressure and pull a mount out.

kyfooter
09-23-2009, 01:15 PM
I have a 2003 with a two-piece (clamshell) motor box. I only have one spring on each side that connects the top portion of the motor box to my hull. If I release the top of the box from the bottom, the top stays up...and if I close the top and release the bottom from the hull, the entire box stays up.

So, yes, the springs should hold the entire motor box up, and certainly the top alone. Gas springs are known to need replacement after a while...but as mentioned, don't go overboard. You can damage the mounts if you have too heavy of a spring (the pressure from the spring is trying to open whether you have the motor box opened or not).

mcgyver
08-19-2010, 10:15 PM
I have recently purchased a 99 Sammy Duvall PS190 and it has the clamshell design with 4 - 7 1/2 " gas springs... I have replaced with SL31-30's and SL31-50's still no good......anyone with accurate pressure #'s would be very helpful...........