86 4.3 low speed questions

I am looking at an 86 Dixie hustler 188 ski boat with 4.3. It has a 21 degree prop (1918p21 stamped on it).

The boat takes off nice and strong, and idles well, fires up easy, runs smooth. It maxes out at about 3800 rpms and 34 mph.

I know this isn't right. I wanna learn how to check for proper fuel pump operation/pressure first of all.

Second I wanna find out what to check for improper throttle operation.

I have been told to check the flame arrestor. Don't know a thing about that! Considering a carb rebuild either way if I purchase it.

I know a compression test is most important. I think anything else I can work with.

Just humor me, what would I maybe be able to find one of these in decent shape for, or what would a rebuild cost?

Might be able to have him drop the price accordingly if compression is low.

Re: 86 4.3 low speed questions

mwe-maxxowner said:

I am looking at an 86 Dixie hustler 188 ski boat with 4.3. It has a 21 degree prop (1918p21 stamped on it).

The boat takes off nice and strong, and idles well, fires up easy, runs smooth. It maxes out at about 3800 rpms and 34 mph.

I know this isn't right. I wanna learn how to check for proper fuel pump operation/pressure first of all.

Second I wanna find out what to check for improper throttle operation.

I have been told to check the flame arrestor. Don't know a thing about that! Considering a carb rebuild either way if I purchase it.

I know a compression test is most important. I think anything else I can work with.

Just humor me, what would I maybe be able to find one of these in decent shape for, or what would a rebuild cost?

Might be able to have him drop the price accordingly if compression is low.

Click to expand...

Ayuh,.... Props are measured in Inches, not degrees,...

Go read through the Adults Only section at the top of this forum,...
Most, to All of yer questions are answered in there....

Yer lookin' at a couple Grand, all said, 'n done to replace the motor with rebuilt...

Re: 86 4.3 low speed questions

I swear I've always seen them advertised as 19 degree, 21 degree, etc... Oops! So it's just the diameter of the prop? And I was also just wondering if these ever pop up used for decent prices. Definitely not worth a couple grand for a rebuild!

Re: 86 4.3 low speed questions

Well not just the DIAMETER but also the PITCH.....PITCH is the theoretical distance the prop would move through the water in a single revolution if there were no slippage......the more the blades are pitched...(the farther they are from flat, like a phonograph record) the farther they will move through the water with each revolution.....think high gear in a car....a lower pitched prop would be like a lower gear....1st, 2nd etc.....those numbers you quote in degrees are popular pitches in inches....

Hope that is some help.....

Re: 86 4.3 low speed questions

mwe-maxxowner said:

I am looking at an 86 Dixie hustler 188 ski boat with 4.3. It has a 21 degree prop (1918p21 stamped on it).

The boat takes off nice and strong, and idles well, fires up easy, runs smooth. It maxes out at about 3800 rpms and 34 mph.

Click to expand...

WOT is a bit low probably do to too much pitch on the prop. WOT should be closer to 4400-4800RPMs. Try a 17 -19P to increase the WOT.

I know this isn't right. I wanna learn how to check for proper fuel pump operation/pressure first of all.

Click to expand...

Carbed engine? - fuel pump pressure 5-6 psi.

Second I wanna find out what to check for improper throttle operation.

Click to expand...

What is it doing now. Shifting into fwd/rev requires a firm throttle handle movement. You should hear one solid clunk when you shift. Don't just easy do it into gear. The shift dogs in the lower unit don't like being 'eased' into gear! There should be some travel in the shifter handle after gear is engaged before any throttle increase. Maybe 2" in movement.

I have been told to check the flame arrestor. Don't know a thing about that! Considering a carb rebuild either way if I purchase it.

Click to expand...

It's that thing on top of the carb which might look something like an air cleaner which it isn't. It is usually very thin layers of metal sandwiched together to prevent flames from coming out the top of the carb in the event of a backfire.

I know a compression test is most important. I think anything else I can work with.

Click to expand...

With this old of a boat you must check for rot! Deck should not have ANY soft spots. Transom like wise should not have any soft spots. A good way to check the transom is to drill a small ?" hole inside down low by the drain plug to check for wet wood. The bits of wood on the drill bit should not be dark looking. You can plug the hole with 3M 5200. Wood rot is very pervasive and will continue to spread.

Just humor me, what would I maybe be able to find one of these in decent shape for, or what would a rebuild cost?

Click to expand...

What are you talking about? The hull or the engine? I paid $1500 for a my 1984 vintage boat and it was JUNK. Had to tear every bit of everything out of the hull and start over. $7000s later I have a very strong safe boat but the engine/outdrive are tired and will probably retire soon. Check my sig link for the full deals. You will be rolling the dice on any boat this age!

Might be able to have him drop the price accordingly if compression is low.

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If the deck or transom have issues [and they will], FREE would be about right.

Re: 86 4.3 low speed questions

I know the importance of checking for rot. This buy is the result of having a "good shape but soft floor" boat that i discovered needed rebuilding. Decided to sell motor and get a better boat instead. Haven't drilled the test holes yet, but the floor is solid, and seems original. I'm gonna check the transom and stringers though. I was referring to finding a motor to put in this boat, if I decide to buy it, and can never seem to find the speed it should be able to give me.

When I said check for improper throttle operation, I meant only checking to see if it's opening all the way. In case it's not and that's the cause of my low rpms. I feel like if it were over propped, it would not come out of the hole strong? Shifts well and easily in and out of neutral and fwd rev.

Re: 86 4.3 low speed questions

To check for full throttle operation remove the flame arrestor and look down the carb with the throttle lever full forward. The throttle plates in the carb should be standing perfectly vertical. Don't confuse the plates at the very top of the carb as the throttle plates as those are the choke plates. The throttle plates are at the bottom of the carb..

Re: 86 4.3 low speed questions

Most boats run a 17 or 19 pitch prop stock. Unless it has been modded or a special hull I would guess it is over propped.

Re: 86 4.3 low speed questions

thumpar said:

Most boats run a 17 or 19 pitch prop stock. Unless it has been modded or a special hull I would guess it is over propped.

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try a 19 INCH prop and see what ya get- you should be in the 4600 rpm range

Re: 86 4.3 low speed questions

I knew the pitch or angle of the prop came into play, hence why I thought it was degrees. I did not know inches were a part of the equation.

Is it reasonable to assume that, if the compression is good, the power is there somewhere?

A higher pitch yields more speed than a lower pitch. A lower pitch is mOre takeoff. But you're saying to too high, and you get out of the motors ability to turn it, just not enough torque to reach max rpms? Correct?

Re: 86 4.3 low speed questions

Took it out again today and got 41 mph. Gps verified of course. It coughed and sputtered a couple times on idle this time. Nothing too bad, but I think this points to a need for carb rebuilding or cleaning. I think maybe this and the prop could be most of the speed issue. And of course plugs and wires may not hurt.

Re: 86 4.3 low speed questions

When it's correctly tuned it should be propped to get 4400 to 4600 rpm at wide open throttle. That's not to say you run it wide open all the time but that's the right pitch to load the motor correctly.
If you pick a lower pitch it will pull out better but it will have a slower top end speed. Also you need to manage the RPM's, don't rev it much past 4800 or it could cause some issues.
If you get too high of a pitch the motor is working too hard at most loads and will not last.

Re: 86 4.3 low speed questions

thumpar said:

Most boats run a 17 or 19 pitch prop stock. Unless it has been modded or a special hull I would guess it is over propped.

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Nope. It has a lot to do with gear ratio too. The previous engine (1994 4.3LX) in my boat (see my signature) had 1.84:1 and I was running a 21" prop and still pulling almost 5000rpm, at just on 40 knots. The current engine is 20 hp MORE but runs a 1.62:1 drive ratio, needs a 19" prop and achieves 43 knots at 4600rpm....

mwe-maxxowner said:

I swear I've always seen them advertised as 19 degree, 21 degree, etc...

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Yeah, I see that a lot too... It's because people are too ignorant to do the research themselves and just copy other ignorant people. As explained earlier, the pitch is the theoretical distance the propeller will move forward (in inches) in one revolution without any slippage. The diameter is also measured in inches. Your '21' prop has a pitch of 21" and a diameter of about 13-3/4". The pitch is the one that has the most affect of loading the engine. Higher pitch, more load, less revs at WOT.... Too much less, and engines die!

mwe-maxxowner said:

I knew the pitch or angle of the prop came into play, hence why I thought it was degrees. I did not know inches were a part of the equation.

Is it reasonable to assume that, if the compression is good, the power is there somewhere?

A higher pitch yields more speed than a lower pitch. A lower pitch is mOre takeoff. But you're saying to too high, and you get out of the motors ability to turn it, just not enough torque to reach max rpms? Correct?

Click to expand...

See above.

mwe-maxxowner said:

Took it out again today and got 41 mph. Gps verified of course. It coughed and sputtered a couple times on idle this time. Nothing too bad, but I think this points to a need for carb rebuilding or cleaning. I think maybe this and the prop could be most of the speed issue. And of course plugs and wires may not hurt.

Click to expand...

I have written a prop "Angle of Attack and Slip Calculator" program. I tried to ran your numbers, but I need the following. Engine revs at top speed, and the drive ratio (should be stamped on the drive, port side on the decal on the drive-shaft housing (top box))... Is this engine a 175hp or 205? (2bbl carb or 4bbl?)

35.6 knots seems very slow for a 18'8 ski boat with a 4.3 litre engine. Mine's a 20' cabin cruiser with a VERY deep Vee (27? deadrise. Yes, I measured it 3 different ways!), and with a '94 4.3LX I achieved 40 knots ...

Chris.......
(oh, and why do people use mph for boats? :facepalm: It's knot guys, knots are the correct NAUTICAL term for speed over water (or in the air for that matter)) http://en.wikipedia.org/wiki/Knot_(unit)