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Old 20 April 2015, 18:15   #1
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Fitting a Mercury Enertia to 115 E-TEC

I've got a 14.75*19 viper on my E-TEC 115 at the moment and I find the viper wants to drop off the plane very easily and the RPMs surge up/down and the prop doesn't really have bite until I am pulling at least 3500rpm. I'm also looking to gain a few hundred RPM at WOT.

I think from reading around a Mercury enertia 14*19 or possibly 14.25*18 will give me all I want, a few more RPM, typically 2-3 mph more top end but with improved midrange performance and general boat handling.

Has anyone here used Mercury props on their E-tec? I've read of some horror stories about prop shafts being damaged because of thinner thrust washers in the flo-torq kits.......
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Old 20 April 2015, 20:15   #2
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I'd stick with the Viper or OMC SST props, I should think a 17" one would meet your needs.
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Old 21 April 2015, 06:43   #3
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My boat came with Vipers & was terrible. Wouldn't grip, continually cavitating in turns, just felt "mushy". Mike Vincent suggested Mercury Rev4s & I never looked back, completely transformed the boat. They are around 10% thirstier than 3 bladers but that's a price I'm happy to pay for the improvement in handling. The boat will stay on the plane at lower speeds & not blow out in the turns. No problem at all with the flotorq hubs.


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Old 21 April 2015, 10:36   #4
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I don't find my Viper cavitates badly but the poor slow speed planing performance really annoys me. From what I have read the Viper is good for top speed but not allot else. I'm not sure I want to go to 4 bladers on a 5.5m lightish boat but the Enertia appears to tick all the boxes from all the reports I have read.

As Hightower said the only prop I could consider from BRP would be a SST. My 115 has the V6 box and lower final drive and the rebel etc are really designed for bigger higher HP boats than mine.

Where is Mike vincent based Dave? I'd be interested to see what he thinks. I'm also weary of getting the wrong thickness thrustwasher with the flo-torq kit and damaging the prop shaft so someone with experience of putting Merc props on an E-TEC would be great.
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Old 21 April 2015, 11:04   #5
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Mike is at South Coast Marine in Christchurch, top bloke


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Old 21 April 2015, 16:24   #6
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I have a ViperSST 13 7/8 x 19 on my E-tec115 and runs well.

Only with a lot of load (7 full equiped divers) the bite could be better to have quicker planee. So I am considering a 4 blade prop. Topspeed is for me not very important, but nice to have.. :-) when driving with two people i reach 72km/hr

But the viper runs nice, and def. not bad.
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Old 22 April 2015, 03:14   #7
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I replaced the Viper props with Apollo props, made a huge difference to grip. They were considerably cheaper as well.
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Old 22 April 2015, 10:13   #8
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I'm guessing you have the long shaft rather than the XL if you have a 13 7/8 19p viper Subaqua?

I can achieve the same top speed as you on a good day since I lifted my engine to the top hole but I have a considerably smaller boat which is countered by the big V6 gearbox and the 2.25 gear ratio on the XL.
At the same engine revs my prop is spinning about 12.5% slower than yours so you must have allot more slip than I do.

Just out of interest what WOT RPM can you pull with 7 divers and kit onboard with the 19p viper? I'd be looking to a 4 blader for pushing those sorts of loads, probably a 15p.

Which props from Apollo did you go for Gordy? Where did you source them? The Enertia is looking like being about 600 with the flo-torq kit.
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Old 22 April 2015, 17:08   #9
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They were three blade, from memory around 350 quid each including hub kit.
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Old 22 April 2015, 17:35   #10
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Take it from me that finding the ideal prop is quite often a dark art.

You mentioned earlier that you read that the Viper is good for top end speed and not much else, I disagree. My setup operates well in all conditions, but that's with different parameters than you have. But I find that I am still experimenting 7 years on and have just bought a 17" Viper to replace my 19" one.

Have you given any thought that you might have a setup problem. You don't get bite till 3500rpm? Do you have any loss of performance during turns, ventilation, cavitation? Perhaps your running your outboard too high in the water? These are all things that can be looked at without spending any hard earned money on another propeller.
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