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Old 04 October 2010, 09:57   #1
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Country: USA
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Boat name: Lady Ashley
Make: Avon SR 5.4
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Engine: 70 Merc 2S
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SR hole shot in head seas

5.4 Searider. 70 merc 2 stroke. 17p stainless prop.

The 70 pushes the boat well, and not too much trouble planing quickly in flat water. I get 39mph 1 up fully loaded with 24 gal fuel and lots of gear.

I have the weight pretty well balanced. Center console midship with 2 batteries and 12 gal fuel tank in console. 12 gal fuel tank at stern, and 5 hp Mariner aux when running offshore. No A-frame. Anchor in bow.

Into moderately steep 3 foot head seas with 1 up, the boat wants to stand on stern, and will not plane. I can't even see over the bow. I can tack into a quartering sea without much problem. I was maintaining 27mph running hard into these conditions. Just can't climb a wave head on after coming off plane.

What is best course? Smaller prop, hydrofoil type fin/stabalizer, trim tabs, 4 blade prop, or any thing I may have missed?
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Old 04 October 2010, 11:47   #2
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Is your flooding hull open or sealed?
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Old 04 October 2010, 11:49   #3
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Block up the hole, then when you come of the plane the back won't be full of water when you accelerate again!
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Old 04 October 2010, 12:24   #4
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Quote:
Originally Posted by HUMBER P4VWL View Post
Block up the hole, then when you come of the plane the back won't be full of water when you accelerate again!
This is what I'm thinking too-that extra bit of power from not having to drain the hull makes quite a bit of difference.
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Old 04 October 2010, 13:21   #5
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Might also suggest you bung a 15" prop on for those rougher days
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Old 04 October 2010, 17:33   #6
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I had a 60 originally on when I got my 5.4 and she was def sluggish. You are not much over that. I found a huge increase in response when I stuck the 90 on. MUCH more fun to play with as I keep the hull open.

Ian
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Old 04 October 2010, 17:53   #7
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Forgot to mention. The ballast holes are already blinded off. I agree with more power. I have a completely refurbished (prop to top) 1989 merc 70. The shop that did the work told me the only diff between mine and the 90 was the carbs. So I will eventually have that done. I am just now getting this motor broke in, and starting to open it up. I have been very pleased with the power, and I am getting 5 mpg+. I had to drive 500 miles to pick up this motor, and when I got there, They had sold the 90 they were holding for me.

i need a back up prop anyway, but was waiting to see how the 17p was going to perform at wot, before I bought a bew one. I am thinking 14 or 15 would give me some flexibility, or a 4 blade. But no experience with 4 blades. I will be able to make the call on 14 or 15 when I finish the electronics, and get the tach installed.
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Old 04 October 2010, 18:07   #8
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Quote:
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I have a completely refurbished (prop to top) 1989 merc 70. The shop that did the work told me the only diff between mine and the 90 was the carbs.
Back in the day, I always considered the late '80s Merc 70 to be an ideal motor for an SR4.7 for that reason (SR4.7 is rated to 70hp max)......

.......then Merc went and spoiled the fun by dropping the 70hp and 80hp versions and replacing them with a 75hp
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Old 04 October 2010, 18:16   #9
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We had the merc 75 on the 5.4, carbs were the biggest pita ever.

Eventually got an opti 90, awesome set up! Wish we hadn't sold it.

We'd agreed if Ian Sharlot was going to haggle at all on the price he'd offered on part ex when he delivered the new one and took the old one away, we would keep it....... wish he had now. It was so responsive and you could tow it v easily.
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Old 05 October 2010, 04:11   #10
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S.r 5.4 hole shot

Hi, I have a S.R 5.4 with carb 75 mariner.Running a 19" 3 blade stainless quicksilver II prop with exhaust vents and Nauticus gas ram trim tabs with flooding hull open.With 10 gallons of fuel in front of the console and 10 gallons behind,and 1 battery.With 500 lbs of crew she takes large seas with controlled ease.Suggest you reduce to 1 battery and look at your fuel load.Once bedded in with the right prop she will do all you want.The above set up gives @ 1litre of fuel per nautical mile and will pull a 200 lb skier up no problems.The trim tabs make a huge all round difference. Good Luck
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