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Mercury on duck boat to low

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Old 01-12-2018, 11:57 PM
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Default Mercury on duck boat to low

Fairly new member but long time lurker. I need the brain trusts help with a problem just got a brand new mercury 40hp on my 15 ft duck boat and was wondering what the best plan of action is to raise it up I got 2 holes left to go up. But all my friends and hunting partners run fixed jack plates I could stand to use a little set back but I hate to but a manual one and it not fix the problem any better than raising the motor. Everyone tells me and my dealer ship recommendeds I get a fixed plate to set it back a little farther but Iím not sure if I should or just got the motor up two holes itís a good inch and a half below the bottom of the bottom and where we hunt and fish is really shallow water. Thanks in advance for replyís I canít poat pictures yet or else I would.
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Old 01-13-2018, 03:56 AM
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What characteristics are you trying to change? Clearly, you believe your motor is too low. Is it creating too much drag, not getting max rpm?
I would try the simple thing 1st: 40 minutes with an engine hoist, move it up a motor mounting hole. Run her, record your numbers. Go put it all the way up: do the same: run her, record numbers. If you are still not happy, then sure, buy the jack plate.

The other consideration that was not mentioned, is play w/ the motor height 1st. IF you are still not pleased w/ the performance, you could consider a "dolphin" or "permatrim" to the anticavitation plate: This will negate the setback you discussed.

The last consideration is trim tabs or at least "smart tabs"
You have options. But, I'd try the simple solution 1st.
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Old 01-13-2018, 04:36 AM
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Hard to picture the situation based on your description, but...

If the anti-ventilation plate on the outboard is below the hull bottom, raise the outboard.

A jackplate with setback will allow you to raise the outboard higher than a transom-mounted outboard can be raised. Motor can be raised 1/2" to 1" for every additional inch of setback, as long as the cooling water intake ports always remain submerged.
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Old 01-13-2018, 04:27 PM
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It's 2018. How about a picture....?
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Old 01-14-2018, 08:57 AM
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Originally Posted by yarcraft91 View Post
Hard to picture the situation based on your description, but...

If the anti-ventilation plate on the outboard is below the hull bottom, raise the outboard.

A jackplate with setback will allow you to raise the outboard higher than a transom-mounted outboard can be raised. Motor can be raised 1/2" to 1" for every additional inch of setback, as long as the cooling water intake ports always remain submerged.
Agree with Yarcraft .
I am always surprised how quickly the water level rises behind the boat as it passes over the water. 6 inches behind the transom the water level is noticeably higher.
The 6 inch set back may very well be the key to good performance as well as the shallowest practical draft.
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Old 01-15-2018, 03:41 AM
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Installed a Mercury 40 EFI on a 15’ GoDevil last week. We added a TH Marine Micro-Jack. Will test run this week. I’m also ordering another jack plate for my cousin who just picked up a 60 EFI last week for his 16’ GatorTrax.

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Old 01-20-2018, 01:20 PM
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I'm using some plates like the ones pictured that I cut out of some some 4x4x.5 inch stainless angle to get more height for my motor. My transom was originally 15" but when the previous owner had the fantails put on they raised the transom height. Problem was they only raised it to 20" instead of 21".
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