Opinion on Jack Plates...

Markyboyo · 30 May 2011, 22:42

I've been thinking of playing with the height of my engine as after looking on the E-tec site it appears that it is set rather too low. The dealer who originally rigged it used 6 bolts instead of 4 (I think the top 2 were too close to the top of the transom so they put 2 more in lower down) meaning I cannot just loosen the bolts and raise it without filling and re-drilling the transom.
Looking around you can get a manual Jack plate delivered from the states for less than £250, I could fit this on the existing holes in my transom and then play around with my engine height easily from then on.

Question is, loads of boats in the States run with jackplates, both offshore/coastal and obviously flats boats but I'm yet to see one in the uk on anything other than a race boat.....I seems to be an easy fix to my problem but I'm wondering if I'm missing something.

Mark.

martini · 30 May 2011, 22:55

It's quite normal on larger outboards to use 6 bolts, 4 in the top.

Jacks are much more common in the US as you say, I think that they tend to like wringing every extra fraction of a knot from their rig, we're not so fussy.

It might be worth posting a pic showing the height of your engine on the transom, if it is too low then a jack may well be the solution. One thing to bear in mind though is will your hydraulic steering cylinder foul on the top of the transom when you tilt the motor? Remember the engine will be set back by jack.

Chris · 30 May 2011, 23:40

Sounds like a good idea in view of your bolt / transom issues.

Good luck !

Markyboyo · 31 May 2011, 15:24

It's possible that the 6 bolts was a deliberate plan but I haven't seen any other engines around 115hp with 6 bolts, the E-tec is only supplied with 4 AFAIK. I'll pop some pics on in a couple of weeks once I get home. The tops bolts really are very close to the top of the transom.

The cavitation plate is level with if not a couple of mm below the bottom of the hull at the moment and I seem to be a couple of knots down on what I would expect after reading around online. When on the plane my engine is more if not lower than:

http://i201.photobucket.com/albums/a...wf/toolow1.jpg

rather than:

http://i201.photobucket.com/albums/a...height21-1.jpg

which is what the E-tec guys advise over on the E-tec forum. Apparently you can run an E-tec surprising high if running a decent SS prop and get some good performance/fuel gains.

I'm currently running a NFB cable for steering but was considering upgrading to hydraulic over the winter, sounds like I could run into problems there maybe. TBH I haven't had any issues with the NFB cable helm so far provided I manage the engine trim sensibly so I could stick with it if need be.

Thanks for the input guys!

Mark

Chris · 31 May 2011, 15:44

It sounds like you have a XL engine on a 20" transom so you are limited in what you can do.

The Jackplate is your only option IMO, and you certainly need to get that engine up at least 3-4" if it is as low as you say, you will probably gain 3-4 knots by doing this and your fuel economy will also be better.

What prop do you currently run and what RPM are you getting fully trimmed out and at WOT?

Chris.

Markyboyo · 31 May 2011, 16:30

I do have an XL 25" engine and the boat was built by Humber for a XL motor.
It is currently rigged as low as possible and the cav plate is virtually level with the bottom of the hull which is what I would expect. I'd just like to raise the engine by an inch ish and see if the performance improved.

It's turning a 19" Viper at the moment and seeing about 37 knots WOT at 5500 RPM trimmed out with a light load.

ColinF who used to be on here used to claim 40 knts and Montu who I believe recently sold his (5.3 so 20cm shorter) claimed to get 44knts, both were running 115s.

I think if I raised it 1.5" (Which would ave been easy were it not for the 6 bolts) and got up to say 5750 and 40 ish knots I'd be a happy chappy!

Mark.

Chris · 31 May 2011, 18:03

Hi, Some pics of how my 150 was mounted to give you an idea. You really only need 4 bolts however as you say this may been due to your top bolts being too near the top of the transom.

It sounds like someone at Humber got their measurements wrong as their should be plenty of adjustment and clearly there is not. If you engine is hanging level or slightly below the bottom of the hull and yet the top bolt holes are near the top of the transom then that indicates that they have put and XL onto a normal transom.

Either way I think your ony option is the jackplate.

Chris · 31 May 2011, 18:17

With regards to the prop then once you lift the engine you could well be looking to go up to a 20" (not easy to come by) or possibly even a 21" at which point you will be flying

Markyboyo · 31 May 2011, 19:04

If I could get up to 40 knots without reving past say 5750-5800 I think I'd stick with the prop as is. Max permitted is 6000 but recommended 5600 I think. That should prob put me back at around 55-5600 with a heavy load onboard

If the engine had been bolted on the 2nd hole then I would have still had another 2 holes to go up and the bolts wouldn't have been so close to the top of the transom. On the Humber the top of the transom is not full thickness until you go down an inch or so from the top which was the problem I think.

Time to start monitoring american Ebay I think....