outboard height and how to adjust

[Jeremy]

I took my V17C for its first serious run from Manly across to Shark Spit and back about 2 weeks ago. I had a quick look over the transom to check the height of the cav plate and it was at least 5 cm below the water at cruising speed. Fair bit of spray flying around also. I am thinking of raising it two holes. Problem is the way the bolts on the transom are currently placed. The outboard is XL shaft and there is a large aluminium plate covering the transom. There is room to go up two holes on the top two bolts which connect to the plate above the transom, but the two bottom bolts into the transom are in their highest position.

I am thinking I just leave these bottom two bolts alone and put two new bolts through a bit higher? Could always cut them off flush once I am happy the new height is correct.

I am not in a rush to do this. Presumably the outboard has been mounted like this since 2005, so it isn't a big issue, but I would like to get it right. I will do some more sea trials before I make any decisions.

[scottar]

Don't just cut them off. I would drill new holes at the top of the bottom slots, fit the new bolts - not tight at this stage, remove the original bolts and raise the motor then seal and tighten all of them. If as you say, it needs to go up two holes, from the looks of things the motor bracket should then be clear of the current bolt holes which can be refitted. If they will interfere in the new position, I'd remove the engine entirely to allow fitment of some countersunk head bolts under the bracket. Make sure you check inside the hull for enough room above the existing bolts to fit the new ones - you don't want to be drilling in at a height where the structure of the well prohibits installation of new fixtures or worse.

[Dignity]

Whoever installed that motor had no idea. As per Scott's suggestion, I reckon two hole shots higher and those bottom bolts will be clear of the bracket, still replace with countersink bolts.

[gazza2006au]

Looks to me that boat was a L shaft converted to XL shaft if that is a engine mounting bolt below the engine mount and they have just put it back thru the hole to fill the void DAF if this is the case i would be wiry of the condition of that transom

just my opinion tho

[gazza2006au]

I remember u now Jeremy this was the boat u traveled to NSW to pick up, That transom has been jacked up 5 inches 100 percent hence the plate on there now and those lower bolt holes 5 inches below the engine mounting holes

the shop may have said your transom is fine but that is one shitty job or whoever messed with putting the XL on a L shaft boat done a really shit job at that

[ericcs]

As previously mentioned, if the transom hasn't been raised properly, you would be better off getting a jacking plate, and use the original mounting holes.
that aluminium plate could be hiding something!

[stevej]

dont even need a jacking plate just go buy a 20mm thick piece of ally offcut from a steel supply

[catshark]

On a general install, the cav plate should sit about 30mm above the keel line, true.

[Smithy]

How'd it go and feel other than the spray? Must be down a couple of hundred rpm if it is that deep in the water. What did you get for WOT revs? What's she sit on for cuise revs? Bit better than the 445C?

[Dignity]

dont even need a jacking plate just go buy a 20mm thick piece of ally offcut from a steel supply

Just take your first born along as payment, in that business there's no such thing as offcuts, just smaller lengths or sheet sizes, still probably cheaper to buy the jacking plate.

[gazza2006au]

I think those engines only came out in 50hp and 140hp could be other models but i havent seen them, your potentially going to raise it a further 5 inches on a already 5 inch increase thats a 140hp hanging 10 inches over the modified transom i would do as what others have suggested and use the original long shaft bolt holes and use a 10 inch jack plate, a manual jack plate will allow u to fine tune the engines height by a adjustable bolt u can get it really dead set right where u need it without adjusting the engine bolt holes

[stevej]

paid $75 for a 900 c 600mmmm square piece for a work bench last year

[Jeremy]

How'd it go and feel other than the spray? Must be down a couple of hundred rpm if it is that deep in the water. What did you get for WOT revs? What's she sit on for cuise revs? Bit better than the 445C?

I have only had it out for one proper run so far and didn't have a GPS on board. Have now installed a chartplotter, so will know more after my next run. May need a bigger prop after raising the outboard.

[Smithy]

Just saw this on Stalkbook.

[Andy56]

Crikey that looks crap. I bought a brand new jackplate from america delivered for less than $350.
This looks like something from the long lost past. Also as an aside, my etec manual says NOT to use a jacking plate which isnt one piece. If your motor had a 2018 manual, it would probably have the same recomendation. As in the picture you posted. Something to do with lateral movement and regidity i guess.
with a manual plate, its easy as pie adjusting your height.

[Dignity]

paid $75 for a 900 c 600mmmm square piece for a work bench last year

That's cheap but what grade and thickness, for a jacking plste you would need something like 5083 and 10 mm is around $340 per Sq metre plus GST, 20 mm is $580 plus GST.

[gazza2006au]

I have been down the track of diy jacking plate on a tinny it made the tinny very uncomfortable to drive the steering was like balancing a ball on a pin was very sketchy

i would recommend just buying a proper jacking plate

[ericcs]

I have been down the track of diy jacking plate on a tinny it made the tinny very uncomfortable to drive the steering was like balancing a ball on a pin was very sketchy

i would recommend just buying a proper jacking plate

exactly, the boat already has an aluminium plate hiding who knows what on the transom. Why bolt another piece of off cut plate as suggested on to the transom, get a proper jacking plate and have almost infinite height adjustment off the original transom bolt locations. And it will look more proffessional!

[stevej]

"as suggested" works and has been used on hundreds of boats and is cheap, just get someone who knows thier stuff to set the height up properly


rebuilding the transom or an appropriate shaft length to suit would be the professional outcome if you spending the guys money for him

[stevej]

no idea and was 20mm at 20mm thick it didnt matter the grade it isnt going to fall off
it was a 30 year old fishing boat and needed a cheap engine replacement to get a few more years from it

[gazza2006au]

20mm is rather thin if your hanging a suzuki rebadged johnson 140hp thats gotta be a 225kg engine i would imagine 20mm plate alloy would fracture or sheer off from the torque of the engine maybe if it was high tensile it would be ok

[scottar]

20mm is rather thin if your hanging a suzuki rebadged johnson 140hp thats gotta be a 225kg engine i would imagine 20mm plate alloy would fracture or sheer off from the torque of the engine maybe if it was high tensile it would be ok

Should be fine Gazza. Jabba ran a 200+ Hp Evinrude on a similar set up on his Seafarer.

http://www.ausfish.com.au/vforum/showthread.php/125475-Seafarer-Appreciation-thread

[gazza2006au]

Thats crazy seems like there would be little insurance in 2cm thick alloy plate

[Dignity]

Thats crazy seems like there would be little insurance in 2cm thick alloy plate

All comes down to the type of ally, 20mm is fine in a 5xxx type, others not so.

[stevej]

and normally only top two bolts are in it and the transom

i had a 225 black max on it and lasted 4 years before i sold it