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Old 01-13-2018, 12:57 AM   #1
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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, 04:56 AM   #2
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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, 05:36 AM   #3
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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, 05:27 PM   #4
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It's 2018. How about a picture....?
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Old 01-14-2018, 09:57 AM   #5
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Quote:
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, 04:41 AM   #6
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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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