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Old 08-10-2012, 10:45 PM   #1
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Advice sought on outboard setup

Guys,

I realise that most on here seem to have Phantoms of various size and set up, but my questions will probably be somewhat universal.

My budget project rig is a Marshan 18 with a 1986 Mercury 200.

The engine sits raised on the transom, but the prop shaft is still 5" below the base of the hull. Despite this, the cavitation plate is 5.5" above the base of the v-hull.

When horsing on, the boat pull quite hard to the right and if I back off sharply it pulls/slides to the left sharply.......a bit disconcerting!

This happens with both a 24" Chopper and and a 22" Laser II. Revs unknown as yet, but planning to sort out the rev counter soon.

I adjusted the torque tab on Sunday and felt little difference at high speed and unfortunately my adjustment resulted in the tab falling off and settling somewhere on the bottom of Loch Lomond......yeah I'm a dick!

I'm looking for a set up that is comfortable to drive at all speeds and if a few top end mph are lost, then so be it. Any advice is appreciated.

Cheers,

Boyd
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Old 09-10-2012, 08:01 AM   #2
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Hi, if you want some advice give me a call 07702958175. Regards Rich
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Old 09-10-2012, 11:42 AM   #3
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That hull was set up for racing with Cavitation plate 4 inches above and a two and a half inch offset from centre to allow for torque
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Old 09-10-2012, 05:03 PM   #4
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Country: Renfrewshire
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Interests: Weights and fast things
Boat name: Hysteria II
Boat make: Marshan 18
Engines: Mercury 200
Cruising area: Loch Lomond & Clyde Estuary

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Quote:
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Hi, if you want some advice give me a call 07702958175. Regards Rich
Rich,

I will do that. Thanks!!
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Old 09-10-2012, 06:07 PM   #5
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Quote:
Originally Posted by BB67 View Post
Guys,

I realise that most on here seem to have Phantoms of various size and set up, but my questions will probably be somewhat universal.

My budget project rig is a Marshan 18 with a 1986 Mercury 200.

The engine sits raised on the transom, but the prop shaft is still 5" below the base of the hull. Despite this, the cavitation plate is 5.5" above the base of the v-hull.

When horsing on, the boat pull quite hard to the right and if I back off sharply it pulls/slides to the left sharply.......a bit disconcerting!

This happens with both a 24" Chopper and and a 22" Laser II. Revs unknown as yet, but planning to sort out the rev counter soon.

I adjusted the torque tab on Sunday and felt little difference at high speed and unfortunately my adjustment resulted in the tab falling off and settling somewhere on the bottom of Loch Lomond......yeah I'm a dick!

I'm looking for a set up that is comfortable to drive at all speeds and if a few top end mph are lost, then so be it. Any advice is appreciated.

Cheers,

Boyd
may need to trim engine out a bit more, when planning
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Old 09-10-2012, 08:58 PM   #6
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Quote:
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may need to trim engine out a bit more, when planning
I've been trimming it right out. Doesn't seem to reduce the torque steer.......but gives a stonking rooster tail!! And can cause a bit of bounce.

Cheers,

Boyd
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Old 09-10-2012, 09:14 PM   #7
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Quote:
Originally Posted by Big Dutch View Post
That hull was set up for racing with Cavitation plate 4 inches above and a two and a half inch offset from centre to allow for torque
Hey Big Dutch,

Not sure about the offset, but I will check and post.

Thanks,

Boyd
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Old 11-10-2012, 12:06 AM   #8
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Lower the motor, will usually handle better. Torque tab will do nothing at that height, it's more than likely out of the water at speed.
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Old 11-10-2012, 09:07 PM   #9
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Quote:
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Lower the motor, will usually handle better. Torque tab will do nothing at that height, it's more than likely out of the water at speed.
Makes perfect sense Hydro. Will having the prop so deep (already 5" below base of transom) have an adverse effect on handling/performance?.......not that the handling could be much more edgy than it already is for a newbie. I have approx 3" available to drop it before its resting on the top of the transom. Seems that Marshans are renowned for their reluctance to lift the bow when trimmed out. Hydro, Would having the prop lower help with bow lift?

Thanks for your input everyone.

Rich, I still intend on taking up your offer of a call. Been travelling all week and not had a minute to myself.

Cheers,

Boyd
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Old 11-10-2012, 09:43 PM   #10
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hello matey. i dont know much about this set up but based on what i have heard about marshans if it was mine i would try props with a little bit of bow lift.
depending on experience something like a laser as a base prop to work on from?
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Old 11-10-2012, 10:54 PM   #11
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Quote:
Originally Posted by Renegade View Post
hello matey. i dont know much about this set up but based on what i have heard about marshans if it was mine i would try props with a little bit of bow lift.
depending on experience something like a laser as a base prop to work on from?
says he's already tried laser.

Yes lowering Lowering engine would increase how much bow lift the prop develops, however it also increases the opposite torque given (the torque from the propeller which makes the boat run on the left hand side)

Have u given the engine a wobble to see if there's any play in the steering ? If there is it will naturally steer right under power and when u back off it'll return , effectively turning left.
Grab hold of the of the cavitation plate right at the back and give it a good tug left & right .

If there's no notch on the transom and your runing a low water pickup, personally I'd start with the propshaft 2"below the bottom, however I have no experience with Marshans....just my 2p
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Old 11-10-2012, 11:58 PM   #12
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oh yeah didnt read it properly. what steering are you using? and is the motor still offset?
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Old 12-10-2012, 10:06 AM   #13
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The Marshan has quite a narrow beam.Before the Qss came out it was all four blade brass Rekord cleaves they used to race with.
Obviously check the steering but also remember the power trim will have an influence on how level across the beam she rides.Trimmed in too much would see it kicked over on one side trimmed out too much and she might get a bit flighty and chine.Its a lot of Power for an old 18 footer originally designed for the old straight six mercs.
Don't put the engine too high cos it could run out of water to cool with especially if it doesn't have low water pick ups.
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Old 14-10-2012, 08:15 PM   #14
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Quote:
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That hull was set up for racing with Cavitation plate 4 inches above and a two and a half inch offset from centre to allow for torque
+1

I have 5.5 inch setback with powerlift.
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Old 15-10-2012, 09:15 PM   #15
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Country: Renfrewshire
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So I dropped the engine by 2" yesterday and took it out today for a quick blast. The high speed pull to the right has lessened slightly. But the sudden nasty tug to the left when throttling off at speed was very much there.
There is defo play in the steering underway and when back on dry land I pushed and pulled at the cavitation plate and steering wheel individually and there is definite play stationary too.
Sorry for my lack of tech knowledge, but the steering is provided by a thick cable from the port side only. On holiday this week, so will get my head under the dash and the back end tomorrow and see if I can locate anything untoward.
Thanks to all for your input.
Boyd
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Old 15-10-2012, 09:37 PM   #16
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i think the steering is the problem. hydraulic steering would be better and help control torque
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Old 15-10-2012, 09:44 PM   #17
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Yep I'd find some Seastar steering. 200hp with single cable steering could get nasty!
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Old 15-10-2012, 11:05 PM   #18
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If you've only got a single steering able on a 200hp outboard then your asking for trouble! There rated to 150hp max! If you have dual cable steering then u can adjust one against he other and remove almost all play between the steering cables

Try to see where the play is. There shouldn't be any play in the engine upto where the L shape bracket is fixed to the cable. If here is play then there is a problem else where either the bolt through the tiller arm (3/8" unf if memory serves ..high tensile steel not stainless stainless) or the shock mounts/bolts.

If the play is in the cable to helm then there might be a fault in the steering/cable, however as with any steering there will always be a tidy bit of slack.
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Old 16-10-2012, 06:03 PM   #19
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I think you will find even with hydraulic steering the chuck you out to the left will still be there, I had a sharpe 19 very similar to a marshan and very narrow, I tried a chopper on it once and nearly fell out although it was the fastest prop i ran i had much better experience with a small hub laser although if you don't have an offshore mid you will need the large hub but they aren't as forgiving. the best option is don't back off harshly!!
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Old 16-10-2012, 08:09 PM   #20
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Country: Renfrewshire
Location: Erskine, Renfrewshire
Occupation: who cares......
Interests: Weights and fast things
Boat name: Hysteria II
Boat make: Marshan 18
Engines: Mercury 200
Cruising area: Loch Lomond & Clyde Estuary

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Location: Erskine, Renfrewshire
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Quote:
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............ the best option is don't back off harshly!!
Lol.........sound advice!

Got another 1.5" before the bracket is hard down on the transom. Going to drop it right down and see what effect this has.

Today I tightened up the linkage of the steering on the bracket at the engine, which was rather loose (embarassingly). Will see if this has helped in any way, hopefully tomorrow. Failing that, I chatted with a local Mercury dealer, who is happy to have a look next week.

I realise that a hull weighing a few hundred Kgs powered by 200hp is always going to demand respect, but I want to make it as safe as possible when at speed.

Cheers!
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