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Under Powered? Engine Height? Prop? Df140A

Old 06-25-2020, 06:00 AM
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Default Under Powered? Engine Height? Prop? Df140A

Hello All, I've posted around but haven't really found the information I'm looking for. Hate to make another thread like this because there's a new one every day...but I need some advice.

Boat is a 1997 Hydra-Sports 20 Ocean Skiff, I just repowered with a 2019 DF140A zuke. I bought the boat not running so I can't compare performance, but it had a 2004 Johnzuki 140 with a 4x13.25x17 stainless prop on it.

The boat currently needs a lot of RPM to get up on plane and cruise on plane. To be comfortable, it really needs 5000-5200 RPM which nets 23-24 mph, WOT is 6200 RPM and tops at 30-31 mph. This is after having the engine raised one hole by the zuke dealer, but I'm thinking it is still too low based on pictures I've seen here.

The engine is currently spinning the Solas 3x14x17 prop that the dealer installed. I have the stainless 4 blade from the old engine that I can test. It really feels under powered but for a boat like this, I figured I'd get better performance. Should I bring the engine up another hole or two? Different prop? I would like to be able to cruise at a lower RPM and figured I'd get higher into the 30's.

This picture is at neutral trim and cruising at 5200 RPM.

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Old 06-25-2020, 06:51 AM
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Your anti ventilation plate is seriously buried under water. It should be visible and above water while on plane. You probably need to raise it at least two holes. The tricky part of engine height is that you should raise it until its too high, then take it down a hole. Unfortunately most dont go through the drill

when you get the plate out of the water, you are going to see a big jump in RPM and speed. Since you are already hitting 6200 RPM with a 17” pitch, you are going to be underpropped after raising the motor. Probably need somewhere between 18” and 19” since that is a heavy boat. What is the advertised dry weight?

I have never heard a good report on Solas props.

Dont use a 4 blade with engine because you will lose too much performance. The 14” 3 blade already has a lot of blade surface.

Since you are lugging in the hole shot, you will benefit by a ventilated prop. I have a SS 14 x 20 Turbo 1 and df140a on a faster boat which is vented and the hole shot is darn right snappy!

If I was in your shoes, and depending on the RPM after achieving proper motor height, I would buy the Michigan aluminum 14 x 19 for about $125 on line (which Suzuki rebrands in their aluminum lineup). Run it for at 50 to 100 hours then buy the good 14” SS with the knowledge of experience and then rework the prop it to achieve 6200 after you have optimized your setup and broken in your motor.

Good job getting the motor height correct first!!!

Old 06-25-2020, 07:15 AM
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That's what I was thinking, it just looks too low. It is currently in the 3rd hole up, which leaves two more holes for me to raise it. Should I go a hole at a time? or does it look like it needs two at least right off the bat? Don't want to have to pull the boat more than I have too, but 2 is the max I can raise it.

The dry weight on the boat is 2250 lbs according to a page I found online.

I will look into the Michigan props or whatever else may be recommended. I gave her a hard break in like this...just want the setup to work
Old 06-25-2020, 07:26 AM
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Definitely go two holes.

When you get it set up right you may be able hit 40mph. The Suzuki performance bulletins show bigger, heavier boats over 40mph with the df140a.

Since you may run out of holes, consider installing an inexpensive manual jack that you wrench up and down. They cost about $2-300. Raise your motor one more time and install the jack and never have to deal with the inconvenience of adjusting motor height again with the added benefit of dialing in height to perfection, and as conditions change.
Old 06-25-2020, 08:14 AM
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That's what I was figuring, the performance just didn't add up on this hull. I'll go two holes and hope for the best. Hopefully that will be enough and I won't need a jack plate, if I do, then I'll have to go down that route when it comes along. Thanks!

Any other suggestions out there for props and what I should be seeing as performance? All advice appreciated
Old 06-25-2020, 08:20 AM
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How clean and smooth is the bottom of the hull?

30.5 MPH at 6200 RPM with a 17” pitch prop is about 21% calculated propeller slip. That is a lot, and it will go up when you raise the motor.
Old 06-25-2020, 08:30 AM
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The bottom is clean and on fresh bottom paint. Next year I am planning on taking all of the old paint off the hull, so I didn't go crazy for this season. There several layers of paint, so it isn't perfect, but it's definitely clean and there were no unnecessarily rough spots.

With that much slip, it sounds like this prop isn't working well. Perhaps the height and the prop are both at fault here.
Old 06-25-2020, 09:02 AM
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Just to confirm, you are running WOT and slowly trimming up until the boat goes slower/starts blowing out, then trimming down slightly to find best trim angle for max speed?

Are there trim tabs and do they retract fully?

To compare I had a 2008 20ft seafox with a DF140 at 2350 pounds and rated for 175hp max. So my knowledge is coming from my experience with a 2008 DF140. They may have changed since then, maybe not.

Light load max speed was 38mph. I tried all kinds of stuff to get more speed and 38mp was the max at 6200rpm with a Solas 3 blade. Cant remember what pitch/model.

The comment about lower RPM applied to a DF140 confuses me. This motor runs high RPM and can sustain WOT runs for extended periods. This is not a putt putt motor. It ran smoothest above 5800 rpm. Thing would just pur back there wide open.

According to NADA, 1997 Hydrocraft 2000-CC at 2650 pounds and rated for 225hp max.

The DF140 may still be the DF115 block pushed to 140hp like it was back in 2008.

I'm not sure your going to get much more out of that setup. The DF140 is excellent on gas, even when run hard, but doesnt really have much in the balls dept.

Maybe take it to a scale and figure out the actual hull weight. It may be heavier than you think.

My weights came from NADA 1997 Hydrocraft 2000-CC. There were a few models to choose from.

I would focus on weight and ensuring it's trimmed perfectly for speed.
Good luck, I hope you get it tuned in to meet your expectations.
Old 06-25-2020, 09:18 AM
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Originally Posted by friogatto View Post
Just to confirm, you are running WOT and slowly trimming up until the boat goes slower/starts blowing out, then trimming down slightly to find best trim angle for max speed?

Are there trim tabs and do they retract fully?

To compare I had a 2008 20ft seafox with a DF140 at 2350 pounds and rated for 175hp max. So my knowledge is coming from my experience with a 2008 DF140. They may have changed since then, maybe not.

Light load max speed was 38mph. I tried all kinds of stuff to get more speed and 38mp was the max at 6200rpm with a Solas 3 blade. Cant remember what pitch/model.

The comment about lower RPM applied to a DF140 confuses me. This motor runs high RPM and can sustain WOT runs for extended periods. This is not a putt putt motor. It ran smoothest above 5800 rpm. Thing would just pur back there wide open.

According to NADA, 1997 Hydrocraft 2000-CC at 2650 pounds and rated for 225hp max.

The DF140 may still be the DF115 block pushed to 140hp like it was back in 2008.

I'm not sure your going to get much more out of that setup. The DF140 is excellent on gas, even when run hard, but doesnt really have much in the balls dept.

Maybe take it to a scale and figure out the actual hull weight. It may be heavier than you think.

My weights came from NADA 1997 Hydrocraft 2000-CC. There were a few models to choose from.

I would focus on weight and ensuring it's trimmed perfectly for speed.
Good luck, I hope you get it tuned in to meet your expectations.
The WOT runs are basically completely trimmed out in flat waters. I do not have trim tabs yet.

The hull you're looking at is a Vector 20, this is an Ocean Skiff model, a bit lighter at 2250 lbs with a 200hp max.
If you were reaching 38mph with your set up, that would be ideal for me. Not looking for a racing boat, would just like a little more performance and a better cruise. As far as the lower RPM, I just meant for cruise. I frequently give it the RPMs it wants, but I feel bad sitting at 5000-5400 RPM all the time just cruising. I feel like I should be able to hang on plane a little lower than that. It's a great motor, just don't want to over work it if I don't have to. I figured a cruise RPM closer to 4600-4800 would be better.

Last edited by DrifterToo; 06-25-2020 at 09:26 AM.
Old 06-25-2020, 10:51 AM
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Outboards like chainsaws love to be run at WOT.
Old 06-25-2020, 11:00 AM
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Wake looks faster than 30mph. Where are you getting your speed numbers from? Gps or pitot speedo?
Old 06-25-2020, 11:04 AM
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Originally Posted by Corndog38 View Post
Wake looks faster than 30mph. Where are you getting your speed numbers from? Gps or pitot speedo?
Speed is coming from a Garmin Echo50s GPS
Old 06-25-2020, 12:30 PM
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Get your motor height right first, then start effing around with props, tabs, etc. Remember, KISS!
Old 06-25-2020, 06:40 PM
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My Naval Architect friend is telling me that I’m dumb to touch anything and that the engine is exactly where it should be and I need to just accept that.

So on that note, I’m pulling the boat tomorrow and am going to lift it on my own. Hopefully the lower the front of the trailer, block the engine, then lift the trailer method will work out for me.

I got some 3m 5200 and 4200. 4200 would probably be the best bet Incase I have to move the engine again, correct?
Old 06-25-2020, 06:46 PM
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4200 would be fine for that use. Do the best you can to seal up the holes.
Old 06-25-2020, 07:16 PM
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Many years ago I had a similar issue. To save headaches from moving motor several times I got a manual jack plate for a few hundred. That way the motor can easily be adjusted until it was the best it will get. See what holes line up and remount or just keep it on the jack plate
In my case I was gonna have to redrill holes in the transom since they didn’t align with the motor bracket holes so I kept it on the jack plate.
Old 06-25-2020, 07:24 PM
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If you think the height adjustment might not be the final adjustment, install the bolts dry for testing. No harm will come. Once you’ve settled on the height, you can bed each bolt with sealant (I like 3M 4200 FC) individually without removing the motor again.

But remember: motor mounting height depends, to some degree, on the model of propeller being used. Some props tolerate higher mounting than others.

If you are moving the motor without benefit of an engine hoist, you will need at least one other person to help stabilize the motor as you lower the tongue of the trailer.
Old 06-26-2020, 06:33 AM
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I will be moving it with the help of a friend to stabilize it, so that should be good.

I have that turning point 4x13.25x17 SS. Apparently 4 blades are stern lifting, should I try that and see if it brings the back up? That would lift the AV plate as well, no? Before I go through the trouble of lifting the engine? Just an idea
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Old 06-26-2020, 08:13 AM
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Turning Point props are crap. Do not spend time and energy fooling with crap.
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Old 06-26-2020, 08:28 AM
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you should try experimenting with the trim button .
trim up till you get blow out then come down a little,at this point take a look as to where the anti cavitation plate is running .

do the above with normal load and weight distribution, then choose a prop and motor height.

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