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17 June 2014, 11:04
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#1
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Member
Country: Finland
Town: Helsinki
Boat name: SR 5.4
Make: Avon
Length: 4m +
Engine: Toh1 3,5 Yam 90/2S
Join Date: Oct 2009
Posts: 919
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Mercruiser engine instalation?
I am about to install a 3.0 L Mercruiser( +alha) and need to build the engine bed for it.
In fact it’s not a bed as it has only one front mount in addition to transom. Previous engine had different mount configuration (one on each side), so have to start from scratch. But the question is, what is the best way to build a solid platform for the engine front mount in a GRP hull?
Have been considering two different configurations:
1 building up the needed thickness with epoxy glued plywood, on top a 5 mm thick flat iron( bolted to the wood). The whole piece then covered /laminated with epoxy and suitable fiberglass fabric . On top of this will fasten the front mount, drilling through the flat iron and making suitable threads.
2 building up the needed thickness with epoxy glued plywood, the whole piece then covered /laminated with epoxy and suitable fiberglass fabric.
Through this will drill horizontally and bolt a 5mm thick angle iron. The engine mount will also be attached to the angle iron.
3 How would a pro do it....?
A very rough “drawing” attached….
Thanks for any comments and views
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fun on a boat is inversely proportional to size...sort of anyway
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17 June 2014, 11:11
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#2
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Member
Country: Finland
Town: Helsinki
Boat name: SR 5.4
Make: Avon
Length: 4m +
Engine: Toh1 3,5 Yam 90/2S
Join Date: Oct 2009
Posts: 919
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picture...
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fun on a boat is inversely proportional to size...sort of anyway
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17 June 2014, 12:41
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#3
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Member
Country: UK - Scotland
Town: north ayrshire
Boat name: charlie girl
Make: S/R5.4/regal3760
Length: 10m +
Engine: Suzukidf70 2x6lp 315
Join Date: Jul 2009
Posts: 3,927
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its more usual to just bolt down the mount with coach screws as in the left diagram rather than use steel glassed in.
Or do it like your drawing showing the angle bar with through bolts but better to use ally angle rather than steel either method would be acceptable
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17 June 2014, 12:58
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#4
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Member
Country: Ireland
Town: Castlebar
Boat name: Clewless
Make: Valiant DR 490
Length: 4m +
Engine: 60 hp ETEC
MMSI: Awaitng one
Join Date: Oct 2007
Posts: 1,339
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From an engineering point of view the first system looks better. The second induces a rotational effect into the strip of timber which can be engineered out
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17 June 2014, 15:49
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#5
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Member
Country: UK - Scotland
Town: north ayrshire
Boat name: charlie girl
Make: S/R5.4/regal3760
Length: 10m +
Engine: Suzukidf70 2x6lp 315
Join Date: Jul 2009
Posts: 3,927
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Quote:
Originally Posted by two stroke mick
From an engineering point of view the first system looks better. The second induces a rotational effect into the strip of timber which can be engineered out
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I have 2x 315 6lp yanmars fitted exactly like the right picture and my previous boat had 2x 300 hp merc diesels the same hadnt been a problem just go with whats easiest to install its not like its a heavy engine
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17 June 2014, 17:39
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#6
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Member
Country: Finland
Town: Helsinki
Boat name: SR 5.4
Make: Avon
Length: 4m +
Engine: Toh1 3,5 Yam 90/2S
Join Date: Oct 2009
Posts: 919
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Thanks for comments and advice so far, all useful points. I am not totally comfortable using coach screws ,its a planning hull and the short chop over here can be stressful on the mounts so rather do a bolt trough solution of some kind.
How about this, i make the beam hollow(thicker GRP), flat alli inside and then bolt through.
Access to the nut through a hole big enough to put a fixed wrench inside(with the nut inside with tape)?
The holes is maybe weakening the structure a little, but don't think the impact is significant to the overall strength.
__________________
fun on a boat is inversely proportional to size...sort of anyway
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17 June 2014, 17:57
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#7
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Member
Country: UK - Scotland
Town: north ayrshire
Boat name: charlie girl
Make: S/R5.4/regal3760
Length: 10m +
Engine: Suzukidf70 2x6lp 315
Join Date: Jul 2009
Posts: 3,927
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a bit complicated when there are much larger engines than yours sat on coach screws
the transom mounts do most of the work in your application
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17 June 2014, 18:22
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#8
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Member
Country: USA
Town: Seattle
Boat name: Water Dog
Make: Polaris
Length: 4m +
Engine: Yamaha 60hp
Join Date: Apr 2007
Posts: 1,152
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Quote:
Originally Posted by C-NUMB
Thanks for comments and advice so far, all useful points. I am not totally comfortable using coach screws ,its a planning hull and the short chop over here can be stressful on the mounts so rather do a bolt trough solution of some kind.
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Skip all these internal steel reinforcements, they are just going to rust out and change the mount shape/integrity.
Epoxy the coach screws in and not have all the holes for water to get into and rot your wood.
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17 June 2014, 18:26
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#9
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Member
Country: Finland
Town: Helsinki
Boat name: SR 5.4
Make: Avon
Length: 4m +
Engine: Toh1 3,5 Yam 90/2S
Join Date: Oct 2009
Posts: 919
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Quote:
Originally Posted by beamishken
a bit complicated when there are much larger engines than yours sat on coach screws
the transom mounts do most of the work in your application
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I agree, edit 3 is maybe little overkill ![smilie](https://www.rib.net/forum/images/smilies/smile.gif) Is there a "marine grade" coach screws available,
i only ever used cold galvanized ones for some wood construction stuff in the past.
A simple solution would be nice, guess it can be tough to get the mount placement 100% correct before having a "dry" test with the engine in place. My plan was to preliminary test the position, then lift the engine and do the final laminating to the hull before final installation.
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fun on a boat is inversely proportional to size...sort of anyway
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17 June 2014, 19:48
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#10
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Member
Country: UK - Scotland
Town: north ayrshire
Boat name: charlie girl
Make: S/R5.4/regal3760
Length: 10m +
Engine: Suzukidf70 2x6lp 315
Join Date: Jul 2009
Posts: 3,927
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You can get stainless ones from a decent chandlery or screwfix do a range of a4 stainless coachscrews
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17 June 2014, 20:03
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#11
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Member
Country: Australia
Town: Sydney
Boat name: Lunasea
Make: Ribtec 890SX
Length: 8m +
Engine: Yamaha ME 421STI x 2
Join Date: Aug 2009
Posts: 475
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My 38ft Cigarette with a pair of petrol 8.1L big blocks weighing 500kg each has stainless coach screws holding the engine mounts in. It is a boat designed to do 80mph through the ocean so I am thinking coach screws may work for you.
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17 June 2014, 21:44
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#12
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Member
Country: UK - England
Town: southampton
Boat name: hydradrive
Make: yamaha
Length: no boat
Engine: sterndrives
Join Date: Sep 2012
Posts: 290
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Are you on about the triangle
Front mount , bond wood to hull an glass in an bond 10mm think steel plate to tap in to.
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17 June 2014, 22:06
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#13
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Member
Country: Finland
Town: Helsinki
Boat name: SR 5.4
Make: Avon
Length: 4m +
Engine: Toh1 3,5 Yam 90/2S
Join Date: Oct 2009
Posts: 919
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Quote:
Originally Posted by yam man
Are you on about the triangle
Front mount , bond wood to hull an glass in an bond 10mm think steel plate to tap in to.
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Yes, the triangle. The way You describe it was close to my original idea, but most over here recommends the coach screw route. Guess both ways works equally well, a 12 mm coach screw will bite pretty well in epoxied plywood.
Here a picture of the ones supporting the original 4.3L, they have ally or steel inside.
The main stringers has no wood and are really heavy duty built. In the picture engine room bulkhead, not transom. I am not sure do i need to remove the original supports or not( i rather not)the 3.0,L and 4.3 are pretty much same size.
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fun on a boat is inversely proportional to size...sort of anyway
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