Islander 191, J150TLCOS

[diver_down]

Boat: 19ft aluminum, Islander 191, 8ft beam, 2000 pounds motor and gear included.
Engine: 150 HP, V6, Johnson TLCOS, mounted with anticavitation about 1 inch above line of the hull, doel fin installed.
Prop: 15x17 three blades, aluminum, a little banged up
Load: 500-1000 pounds
Problem: 4000 RPM WOT (should be about 5500) with a speed of about 35mph according to the onboard speedometer (did not GPS it yet)
Symptoms: the boat seems to "plow" with the transom in the water while the bow raises VERY high, creates a HUGE wake, plenty of washout.

I would like to correct the "plowing" issue and get to the recommended WOT RPM (5500).
Do you think this is a propeller issue or is it most probably something else (the hull is clean, with no dings or paint on it)? I tried prop slip calculator and at 15% slip the speedometer seems to be accurate. I am wondering if I am running too much a prop for this engine and load?

 

[hwsiii]

Re: Islander 191, J150TLCOS

Diver, welcome to Iboats prop forum and we will try to help you as much as we can but without more information no one can help you, and I will tell you I need more information than anyone else. But if you would like my help fill this form out and I will help you as much as I can, if you would prefer to not go to this much trouble there are other people who will gladly help you.

Iboats Boat and Motor Info

1. Year, make and model of boat
2. Length, width and base weight of boat, look for boat decal on back of boat
2a.What is the maximum recommended HP for your boat
3. Number of people and gallons of gas normally on boat
4. What do you use the boat for
5. Is it a Deep Vee and if so how many degrees of deadrise
6. Year, make. manufacturer and model of motor
7. HP and gear ratio of motor IMPORTANT
If you don?t know the ratio, you need to pull the plugs out and put a piece of tape a c ross the prop and the lower unit and then cut it between the prop and the housing and turn the motor until the tape lines up with each other, it is easier if two people do this, so one can watch the prop while the other counts the revolutions of the motor
8. Manufacturer?s recommended Wide Open Throttle (WOT) range
9. Anti-ventilation Plate height above keel of boat if it is an outboard in inches, use a board under the keel and stiking out to the anti ventilation plate for a referene
10. Is it a bass boat or does it have a pad bottom
11. Does it have a hydrafoil, dolefin or trim tabs
12. Make, model, diameter, pitch and whether SS or aluminum prop
13. WOT RPM and speed from your current prop and how much gas and how many people were in the boat for the test data and is the speed by GPS. Make sure you trim the prop up until it starts ventilating and then just trim in until it quits ventilating. If you do not have a tach you can buy a Tiny Tach for $ 50
RPM ___________ Speed ___________ No. of people ____________
14. Are you at sea level or a higher elevation, give us the elevation in feet
15. Has your motor been tuned up lately and have you checked that the carburetor butterfly is opening all the way, checked compression, and looked at the plugs and checked spark, all of the foregoing could be the reason your prop is not attaining full RPM
16. How long has this prop been on the boat and why, at this time, do you think it is the wrong prop
17. Does the prop show any damage that you can see
18. What problems are you trying to cure or what are you looking for the boat to do that it is not doing the way you think it should or to your expectations
19. If you are trying to attain a better cruising speed and fuel savings or trying to attain a faster speed I will want you to take your boat and run it with 1 or 2 people and give me the RPM and speed readings starting at 3,000 RPM in 500 RPM increments all the way to WOT.

REMEMBER, The numbers I give you will be NO better than the information you give me

The only thing I ask of you is to come back and give me a report of WOT RPM and speed for my database.


H

 

[diver_down]

Re: Islander 191, J150TLCOS

1984 Starcraft Islander 191

19ft, 8ft beam (no decal on the back, the boat is aluminum)

150hp max recommended

30 gal tank, usually half to 2/3 full, 2-4 people. 2-300 pounds of scuba gear
diving / fishing (ocean)

the hull is a V-shape, how deep and what is the deadrise is a mistery - can't find any info on it, though I tried

1984 Johnson 150hp V-6 model nr. J150TLCOS

150 hp, According to manual the gear ratio is supposed to be 1.86

4500-5500 recommended WOT rpm

cavitation plate 1 inch above keel

it is NOT a bass boat, staight aluminum hull (I can post some pics if needed)

it has a foil on it, no clue if it is a hydrafoil or a doelfin (was there at purchase, i put it back after servicing the engine, will try to take it off and retest the boat tomorrow, weather permitting)

aluminum prop, no clue of model or make, only readable numbers on it are 15x17, I assume 15 in diameter, 17 pitch

35mph at 4000 rpm, 20 gal of gas, about 150 pound of gear, about 400 pounds of people (2 big guys) at the date of the test. speed is not by GPS but "internal" speedometer, will try to get GPS speed and independent tach reading tomorrow (weather permitting)

sea level testing conditions.

will double check ignition, carbs, plugs, compression tomorrow (raining cats and dogs all day today)

prop was on the boat at purchase, a little dinged up. trying to attain 5500 WOT and an increase in speed. boat is also "plowing" with the transom while bow is up high above the water

I am trying to attain a better cruising / fuel economy. the normal load would be 3-4 people (6-700 pounds, 3 big guys + somebody smaller) and 3-400 pounds of gear (mostly scuba)
I will GPS it first chance starting at 2500 in 500 increments as high as it currently goes and report back.

THANK YOU!!!!!
Best of all,
Nick.

 

[hwsiii]

Re: Islander 191, J150TLCOS

Nik, I started running some numbers on your boat and with the RPM you gave me with a 17" prop and the 1.86:1 gear ratio and I show a -1% prop slip and that is not possible, so something is wrong somewhere. Verify the gear ratio, and are you using a GPS for your speed, you an use a hand held one or even some phones have a GPS. I will be waiting for your new numbers.


H

 

[diver_down]

Re: Islander 191, J150TLCOS

I could not get the GPS to work today (driver not installed on the laptop). Seems like the onboard gauge is quite inaccurate - i compared to the one on the raytheon depthfinder.
here are the numbers I ran today with the depthfinder:
3000rpm ------------- -25mph
3500rpm --------------32.4mph
4000rpm ------------ -40.1mph
4500rpm ------------- 45.8mph
5000rpm --------------51.1mph
WOT at 5000 rpm
The onboard speedometer tops out at 35 and stays there.

I rechecked the motor and seems like one of the sparkplug wires was shot - replaced it; also replaced ALL sparkplugs again (the "old" ones look a little fouled). took the hydrofoil off (says stingray hydrofoil on it). Those are the only changes I made.
The load was 36 Gal of gas (gas tank full) + 2 people (about 200 pounds each, 400 total), maybe 100 pounds of other miscelaneous tools and gear.
The boat would shoot right up from the hole, the issue is that it would drop off plane at about 22mph / 2600 rpm

second run was with outboard trimmed out all the way. at the same rpm's the numbers are larger by 2-3 miles, except the WOT is 5150 - 5200 at a speed of 57 mph. No cavitation noticed.

I am aware I might have the gear ratio wrong - will check with a tape on Tuesday or Wednesday.

off topic:
I also realized I need to rewire the entire thing - the wiring is a mess and some thing do not work, at least not to my liking
I also realized that I don't really need more speed - the only ones able to pass me on the puddle were the jetskyes; it was funny to see 50g boats, shiny and with quite proud owners try to pass us and make a sower face when i would open it all the way.

 

[diver_down]

Re: Islander 191, J150TLCOS

ran the numbers in prop slip calculator ---- something is REALLY AMISS, nothing makes any sense. I have to start looking at things again and GPS this thing ASAP (Tuesday or Wednesday).

 

[hwsiii]

Re: Islander 191, J150TLCOS

That is why I told you get a GPS, but you also need to hek the gear ratio aording to number 7. above as well. LOL


H