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Old 02 June 2012, 21:00   #1
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Re Mercury 90 Four stroke problems

Hi Guys,
Have just sold my old RIB and am deciding between a couple of RIBS what I should buy. One particular 5.5 metre RIB has a 2003 Mercury 90 four stroke with carbs.
I have heard of several bad things about them like Carburettor problems, and blockages in the rubber Grommet at the top of the water tube, leading to expensive engine head removal in order to sort it.
Also is a very heavy engine for a 5.5 metre RIB. How does it affect the power to weight ratio and balance or handling of the RIB.

Love to hear some comments.
S.
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Old 03 June 2012, 20:01   #2
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Quote:
Originally Posted by stucksays
Hi Guys,
Have just sold my old RIB and am deciding between a couple of RIBS what I should buy. One particular 5.5 metre RIB has a 2003 Mercury 90 four stroke with carbs.
I have heard of several bad things about them like Carburettor problems, and blockages in the rubber Grommet at the top of the water tube, leading to expensive engine head removal in order to sort it.
Also is a very heavy engine for a 5.5 metre RIB. How does it affect the power to weight ratio and balance or handling of the RIB.

Love to hear some comments.
S.
Have just bought a Ribcraft 5.85 with mercury 90 efi it is a Yamaha engine on mercury running gear. I like you had heard bad things about this engine but the one I got is minted . Now the faults that I have found doing a google search is that the gear change is stiff due to a nylon grommet on the linkage and that the mating plate between the engine and the running gear is prone to electrolysis if the anodes are not changed at service intervals apart from that I think it is a good engine have done 30 hours no problems. Also having looked at the manual it doses not look like a big job to remove the power head and fix any grommet problems at the same time as checking for electrolysis problems

Hope this helps
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Old 03 June 2012, 20:07   #3
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Sell the 4 stroke and buy a 2 stroke. Light and reliable.
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Old 03 June 2012, 21:23   #4
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Originally Posted by stucksays View Post
Hi Guys,
Have just sold my old RIB and am deciding between a couple of RIBS what I should buy. One particular 5.5 metre RIB has a 2003 Mercury 90 four stroke with carbs.
I have heard of several bad things about them like Carburettor problems, and blockages in the rubber Grommet at the top of the water tube, leading to expensive engine head removal in order to sort it.
Also is a very heavy engine for a 5.5 metre RIB. How does it affect the power to weight ratio and balance or handling of the RIB.

Love to hear some comments.
S.
Had a BWM Deepsea 17 with this motor on the back. Engine was a little heavy, but in my opinion it helped the balance of my set-up over a Yam 80 2 stroke.

With the Yam I always felt it was way too easy to stuff in a following sea and would need to back right off as it just didn't give me the confidence I needed to make the wave in front.

The Mercury added more weight to the stern and that helped keep the nose up and thus gave more confidence.

I also had to have the transom looked at. Some cracks appeared around the knees. Turned out to be just the gell coat cracking as there was obviously a little more flex due to weight and increased HP. As the fiberglass had to be ground back for inspection I did however beef up the transom a little, just to be on the safe side.

I had some problems with the engine later on that made me regret purchasing it over the Yam. I should have kept hold of my cash and put it towards the new RIB that I evenually bought.
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Old 03 June 2012, 21:46   #5
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I had some problems with the engine later on that made me regret purchasing it over the Yam. I should have kept hold of my cash and put it towards the new RIB that I evenually bought.
4 strokes and your out!
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Old 04 June 2012, 04:29   #6
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Quote:
Originally Posted by Hightower View Post
Had a BWM Deepsea 17 with this motor on the back. Engine was a little heavy, but in my opinion it helped the balance of my set-up over a Yam 80 2 stroke.

With the Yam I always felt it was way too easy to stuff in a following sea and would need to back right off as it just didn't give me the confidence I needed to make the wave in front.

The Mercury added more weight to the stern and that helped keep the nose up and thus gave more confidence.

I also had to have the transom looked at. Some cracks appeared around the knees. Turned out to be just the gell coat cracking as there was obviously a little more flex due to weight and increased HP. As the fiberglass had to be ground back for inspection I did however beef up the transom a little, just to be on the safe side.

I had some problems with the engine later on that made me regret purchasing it over the Yam. I should have kept hold of my cash and put it towards the new RIB that I evenually bought.
Thanks for that Andy
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Old 04 June 2012, 04:30   #7
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Originally Posted by spartan View Post
Have just bought a Ribcraft 5.85 with mercury 90 efi it is a Yamaha engine on mercury running gear. I like you had heard bad things about this engine but the one I got is minted . Now the faults that I have found doing a google search is that the gear change is stiff due to a nylon grommet on the linkage and that the mating plate between the engine and the running gear is prone to electrolysis if the anodes are not changed at service intervals apart from that I think it is a good engine have done 30 hours no problems. Also having looked at the manual it doses not look like a big job to remove the power head and fix any grommet problems at the same time as checking for electrolysis problems

Hope this helps

Thanks for that.
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Old 04 June 2012, 05:18   #8
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4 strokes and your out!
you'll have to speak to my missus about that!
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Old 04 June 2012, 07:34   #9
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you'll have to speak to my missus about that!
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