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Old 11 November 2006, 05:57   #1
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Mariner Marathon 135 questions

Hi all,

Forum newbie here, although I've been lurking for a few months.

I bought my first Rib, a Ribtec 585 with Mariner Marathon 135 (serial number OC164663), a few weeks ago. We've been out a few times, but now getting very cold up here in Scotland.

I have a couple of questions about the engine, and was hoping some here may have experience with this type of engine.

The engine is in great condition for its age, and runs very well. However, it doesn't idle well, especially when cold, and frequently stalls. This may be a 'feature' of big old 2 strokes, but does anyone have any advice as to what might be causing this?

The handbook indicates a full throttle range of 5000-5500 rpm. Does this mean 5500 is the rev limit? Is it safe to open it up above 5500? Does it have a rev limiter?

Lastly, does anyone know how much this engine weighs? I have tried the marinepower website, but could find no reference. The transom is quite low in the water (hull only rated for 120hp), and I am thinking about getting a lighter, more frugal motor.

Sorry for all these questions in my first post. I am a sailor by default, so boats with no sails are all a bit new.

Cheers!
Neil.
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Old 11 November 2006, 15:08   #2
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Neil hi and welcome to Ribnet. Ribtecs do have low transoms, caused because its a deep V hull without a planning pad. Had problems in the past with a 6.45 if too many divers sat at the back end water would slosh over the transom. Depending on your DIY skills you could try raising the transom and filling in the bit under the engine saddle or just live with it making sure to slow down carefully when coming off the plane.

The 93 Mariner catalogue lists the 135 hp engine as 184 kgs, with a 2 litre powerhead and 2:1 gearbox. Your maximum revs should be between the two figures, with your normal crew/load/fuel on board. Change the prop if she over revs. Its an old engine but if she is running well keep her and just use her regularly

V6s do cough a bit at idle but a good service, new plugs and clean of the carbs could be all it needs. Poor running could just be down to lead free petrol freezing in the carbs before the engine has warmed up enough for the heat to get though to the carbs. Caught lots of us out in Northern Ireland when Shell first introduced it.

Don't think they have an over rev limiter but they do have a tilt switch to stop you starting the engine trimmed up, (mercury tilt switch ?), however if it fails you won't start it at all, thankfully the cure is just to disconnect it.

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I am a sailor by default, so boats with no sails are all a bit new
never mind at least you have seen the light

Pete
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Old 12 November 2006, 04:59   #3
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Pete,

Thanks very much for your reply.

The previous owner has fitted a metal plate to reduce wave slop over the transom, and it works well on an unladen boat. I think it will struggle with more people/kit on board. Also, the transom has been repaired in the past, and that repair is starting to crack again, so I feel that a lighter engine will be better all round.

Thanks for the idling tips. I think I'll have a go at the plugs and carb, and see how it goes.

Cheers!
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Old 12 November 2006, 05:13   #4
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If you do change then a Yamaha 90 at 120 kgs would be a good choice, unfortunately there excellent reputation means they are expensive secondhand and peeps like to hang on to them, but you are paying for high quality and reliability. For comparison the Mariner 2 stoke 75/90 are 131kgs and the Mariner 115s 143 kgs.

So long as everyone doesn't stand at the back of the boat you shouldn't have to much of a problem with the low transom. Jimbo on here has the same rib and manages quite well and a rib is easy enough to drain the water off.

Pete
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Old 12 November 2006, 06:32   #5
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... However, it doesn't idle well, especially when cold, and frequently stalls.
Welcome Neil. My place to start would be the tickover mixture adjustment especially if it stalls with a wee sneeze. Two strokes are fairly sensitive to their mixture at idle and yours sounds as though it's just a tad off.
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This may be a 'feature' of big old 2 strokes,...
Yes, to some extent this may be true. There are 2 strokes which don't like prolonged idling and others which will idle for ever. I think it's a feature of the oil scavenging. For lubrication, the petrol evaporates out from the oil which is left in the crankcase to do it's job. Obviously this oil spatters into a mist and is carried out of the motor through its normal running. At idle, some engines appear not to remove as much oil as is being supplied in the fuel so the oil fuel ratio is gradually getting out of spec. and the engine running begins to suffer. Sometimes a good rev will clear the excess oil and allow the engine to continue running. Other times the spark plugs may have become too oily for satisfactory running. Cleaning them or a run at reasonable speed may sort it.
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Old 12 November 2006, 07:46   #6
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So long as everyone doesn't stand at the back of the boat you shouldn't have to much of a problem with the low transom. Jimbo on here has the same rib and manages quite well and a rib is easy enough to drain the water off.
Yep, Neil and I have already spoken via pm. I think that my Yamaha 115hp (which is one of the lightest 2 stroke 115's around) is ideal on the back of a Ribtec, and I've never really noticed too much of a problem with flooding. either side of the engine I have 2 small metal plates which help prevent some degree of splashback. I've not swamped my Ribtec in reverse (although I have done with the university Rib, eh Pressman!!) and have been out in some reasonable weather with plenty of people and gear on board, so don't think it's a big worry.

If you look at the profile of the 585 in the water, only the back of the tubes are touching at rest (and when lightly laden) - so that makes it look quite low at the stern, which is normal.

As I said in my e-mails, I'd be looking at a new tech 2 stroke such as a 115 Opti, or my dream engine a 115 etec, as I think a 4 stroke would be too heavy for you to get as much enjoyment out of the boat!

Jimbo
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Old 12 November 2006, 14:00   #7
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Thanks everyone for your good advice.

It looks like I'll stick with the 135 for a year or so. I'll have a go at servicing it (failing that I have a mate who's very handy) and get it idling better. I think though at some point the noise/fuel economy, range (60l tank)/smokyness of it will push me towards an upgrade.

By the way, is there a market for an engine like this? 1k?

Cheers
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Old 12 November 2006, 14:08   #8
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By the way, is there a market for an engine like this? 1k?

Cheers
Depends how much the mad 2-stroke selling damages the marketplace before the end of December...


There'll definitely be a market for it come April/May.
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Old 14 November 2006, 04:27   #9
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Yes it has a rev limiter. As said before, get it serviced and have the carbs set up properly and get the timing checked etc etc. Good engine should go on for years!!
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