Mariner Prop to Pad question

logan1297

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Aug 5, 2018
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I know this isnt a good prop to pad picture, but boat is winterized and put up so best I have. But I am wondering if the motor being too low is my issue, i can trim completely up and just throw a 15ft rooster tail without the prop blowing out and only turn about 5200 rpms.

23p Trophy prop on a 89 Mariner 200
 

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jimmbo

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Well you are right about it being being a poor photo. If you are over trimmed and the prop is not losing its bite, then you might be too low. But without Photos, properly taken... You hull looks like it has a built in Setback, so that will also be a consideration. But with proper photos, your best bet is to wonder about it until spring, then post more pics
What is the WOT range for your engine? 5000 - 5500, 5300 - 5800, 5400 - 5900?
 

logan1297

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I agree, recommended WOT is 5300-5800 and with a 23p prop I am pretty sure I should be touching the upper end of that range
 

jimmbo

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What makes you think you should be turning 5700 - 5800 with a 23?

Just curious, how long have you owned the boat/motor?
 

logan1297

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What makes you think you should be turning 5700 - 5800 with a 23?

Just curious, how long have you owned the boat/motor?

With the lower pitched prop I shouldn’t be lugging the lower end of the optimal RPM range and about 6 months.
 

QBhoy

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52-53 mph

Seems a touch slow maybe. Hard to tell by the picture. But trying to imagine what the AV plate would sit like trimmed further down, might suggest you are a bit low mounted. What prop is it you’re using ? As in make and type.
 

logan1297

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Seems a touch slow maybe. Hard to tell by the picture. But trying to imagine what the AV plate would sit like trimmed further down, might suggest you are a bit low mounted. What prop is it you’re using ? As in make and type.

Thats what I was thinking , I fully believe with a 200 on the 19.5ft charger I should see low 60s. I am running a 23p Trophy 3 blade
 

jimmbo

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So you recently purchased it. Has it always performed like this? Prior to purchase did you check or have someone check, the condition of the Engine?
Did you take it for a test drive?
If not,what did the Seller tell you it would do, speed wise?
Is the Hull free of Hooks?
 

logan1297

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So you recently purchased it. Has it always performed like this? Prior to purchase did you check or have someone check, the condition of the Engine?
Did you take it for a test drive?
If not,what did the Seller tell you it would do, speed wise?
Is the Hull free of Hooks?

Yes and he said it would run 55 but he had not had it very long and it has looked as if the motor has been mounted 1 hole higher before and judging from the guy I bought it off of he was not the one to move it and had did not mention moving it. The motor is spotless under the cowling and looks to have very little hours. I pulled the carbs reset the floats as they were running slightly lean with one running very lean and thoroughly cleaned them as well as checked the timing and advanced the timing slightly to where it is recommended at. If it tells you anything about the seller we ran out of gas on the test drive. There are no hooks in the hull.
 

logan1297

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Yes and he said it would run 55 but he had not had it very long and it has looked as if the motor has been mounted 1 hole higher before and judging from the guy I bought it off of he was not the one to move it and had did not mention moving it. The motor is spotless under the cowling and looks to have very little hours. I pulled the carbs reset the floats as they were running slightly lean with one running very lean and thoroughly cleaned them as well as checked the timing and advanced the timing slightly to where it is recommended at. If it tells you anything about the seller we ran out of gas on the test drive. There are no hooks in the hull.
 

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Texasmark

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From Mercury verbiage: Normal setting for OB engine is AV plate 1" below hull....defined something like.....putting a yardstick against the hull, near the keel or keel area, extend past the AV plate, engine trimmed to have the AV plate parallel to the stick.

From big guns on here, years ago, 1" jack for every 6" extension from the transom.....meaning transom in the water since water starts rising immediately after the transom passes....if you have hull setback, like most bass boats, you already have 6" of setback with the transom offset. Add a jack plate (without regard to jacking height) and you have another 6" or so.....then add jacking as required.

More from the big guns on here years ago: If you have a rooster tail, you are wasting thrust!!!!! Main cause, over trimming (out too far).
 

logan1297

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From Mercury verbiage: Normal setting for OB engine is AV plate 1" below hull....defined something like.....putting a yardstick against the hull, near the keel or keel area, extend past the AV plate, engine trimmed to have the AV plate parallel to the stick.

From big guns on here, years ago, 1" jack for every 6" extension from the transom.....meaning transom in the water since water starts rising immediately after the transom passes....if you have hull setback, like most bass boats, you already have 6" of setback with the transom offset. Add a jack plate (without regard to jacking height) and you have another 6" or so.....then add jacking as required.

More from the big guns on here years ago: If you have a rooster tail, you are wasting thrust!!!!! Main cause, over trimming (out too far).

I will have to get it out when I go to move the motor but when I measure last i was roughly 6.5” below pad. I have just been playing with the trim to see where it likes it and thats when Ive noticed that I can never blow the prop out. Id like to keep the rooster tail below the cowling and rain about 500 rpms.
 

jimmbo

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6 1/2 inches below the Pad? either you have an Extra Long Shaft925") engine or you are measuring the wrong part of the hull.
Or are you measuring Propshaft depth?
 

Texasmark

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No blowout means you are sitting too low in the water, even with a quality SS prop. (opinion). The more you jack it the easier it will be to blow out and the sweet spot is up till it blows out then back down till the MPH comes back up and the RPMs settle down. (experienced)

Since the thrust angle decreases as the engine is raised, the rooster should decrease, both from prop disturbance and AV plate new water interaction.

Do a www search of bass boat ads and check out the roosters in their videos, then check out their setback and engine heights....might as well pickup on their props while you are at it.

Big guns on here can correct me on this (and not hurt my feelings) as I never had a jack plate per se. Just what seems to make sense to me having run the 4th hole up on a transom mount with a 24XL (pitch) Ballistic SS....my Avatar.

PS: Using a transom mounted transducer?
 

logan1297

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Aug 5, 2018
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6 1/2 inches below the Pad? either you have an Extra Long Shaft925") engine or you are measuring the wrong part of the hull.
Or are you measuring Propshaft depth?

I am measuring from the pad to the center of the propshaft.
 

logan1297

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Aug 5, 2018
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No blowout means you are sitting too low in the water, even with a quality SS prop. (opinion). The more you jack it the easier it will be to blow out and the sweet spot is up till it blows out then back down till the MPH comes back up and the RPMs settle down. (experienced)

Since the thrust angle decreases as the engine is raised, the rooster should decrease, both from prop disturbance and AV plate new water interaction.

Do a www search of bass boat ads and check out the roosters in their videos, then check out their setback and engine heights....might as well pickup on their props while you are at it.

Big guns on here can correct me on this (and not hurt my feelings) as I never had a jack plate per se. Just what seems to make sense to me having run the 4th hole up on a transom mount with a 24XL (pitch) Ballistic SS....my Avatar.

PS: Using a transom mounted transducer?

That is kind of what I was thinking, I ran into the same problem with the Bullet I had when I got it. Also another tell tale to me is that I am catching the cowing on the splashwell by the back compartment when I trim the motor up and I shouldn’t have that issue. Yes Im running a transom mounted ducer.
 
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