4588 Propeller sizes, is 22x21 correct?-gctid404108

[Foster]

After the hull cleaning and making sure everything worked I now have a question.

Do I have the right props on the boat? The ones are 22"x21"

With a clean bottom and slack tide, 1/2 gas and 1/2 water at WOT (3000) I was getting 14.2 knots. I have a 93, so have the slightly larger Hino's

All I can find as references are the 4550 (22x21) and the 4788 (24x22).

Thanks!

[Guest]

Hello the rpm is right, and the props are what our 4588 had. We also had the 250 hp hinoes. Our top speed was 17.5-18.5 though. That was with a tender with 15hp four stroke not sure about fuel and water. I could not seem to make the trim tabs ever make much more than one knot of speed difference. I am at a loss to understand how you can be getting all 3000 rpm with those props, but top out at 14.2 knots. We are getting 12 knots at wide open throttle with twin 120 hp Yanmars, but a much lighter 4588 (1991) have you played with the tabs?

Cheers steve

[Guest]

Our 1991 with the 250hp Hinos runs 19.5 knots WOT at 3000 rpm with just under half fuel, full water, tabs down, and dinghy on the upper deck. I don't know what props are installed. At 1650 I am doing about 8.7 knots. Measured with GPS.

[ABBOAT]

I have a 93 4588 and run the bay alot. I get 19 knots . I have same props. When did you last check your transmissions

[Foster]

ABBOAT wrote:
I have a 93 4588 and run the bay alot. I get 19 knots . I have same props. When did you last check your transmissions

They are there, they don't make any grinding sounds, and shift smoothly. What am I looking / listening for?

[Guest]

Not sure what you would be looking for in the transmissions. For both to be somehow not giving full shaft speed would be a stretch. Both to fail at once stretches that I bit further. If you have 3000 rpm in, then you almost certainly have the appropriate output speed., if not,....that 250 hp input would turn into heat fast.

I am wondering more about trim tab setting? Are they moving up and down? Is the bottom clean? Do the props have barnicals on them? Something fishy here as you are acheaving full rpm on both tachs,.... And getting 14 knots? Or was it 14.5? I am suspicious of the condition of the props, or bottom of the boat here, but wonder how you can be getting 3000 rpm. What speed does the boat "just" start to plane?

Steve

[Foster]

Bottom cleaned a week ago. Props good, etc. I looked at the trim tab bottle just now and its low on fluid. What type of fluid goes in there?

[Foster]

So after a fun day of trim tab maintenance we took the boat for a run.

I did a pass up and down the river to compensate for tide/wind variations. It was slack tide, so there was not much of a change.

With 1/2 load of fuel, 2 adults, dink, front water tank 1/2 full, lower water full: I was able to go 17.2 kts in one direction 17.3 in the other.

I was able to trim the boat up and down, best speed was bow down (full tabs). Speed ranged from 14 (bow skyward) to the 17.2 with the bow down.

Fuel consumption was 10GPH per engine.

Bottom was cleaned 2 weeks ago.

Any ideas on the last 2kts or do I just figure it's not going to happen?

[Guest]

Very curious to know what happened to your rpm. Last I recall you were at 14.2 knots at 3000 rpm. Where is the rpm now at 17.2 knots? I recently dealt with a couple of props that were not as stamped, and we're out by 2" of pich. Seems to me that if you got another 3 knots, your rpm should have climbed as well. My recollection is that 3000 rpm was the full speed, when fully loaded rpm you want to be at (on the hinos) If you are now at 3200-3300 then I suspect the propellers must be a bit light on pitch.

Cheer stev

[Foster]

Best time was 12 kts. before I started changing things.

I had the bottom cleaned, once it got cleaned, then I got to 14.5.

Trim tab adjustments got me to 17.2 kts

I've been able to get 3000 RPM all the time, just not the corresponding speed.

[smitty477]

"I've been able to get 3000 RPM all the time, just not the corresponding speed."

When was the last time the props were scanned and/or inspected?

Can you get the rpm's above 3,000 in any trim condition?

What is the non loaded rpm limit?

Have the tachs been verified and/or strobed?

Do you have pyro's or boost gages on the engines- what do they read at WOT?

Are you in fresh water?

Perhaps the rpm's are not what they seem, perhaps the props have issues, perhaps something is holding back the engines.

[Foster]

When was the last time the props were scanned and/or inspected?

-- Never that I know of. When it was out of the water in July I looked at them for dings and bends, nothing visible.

Can you get the rpm's above 3,000 in any trim condition?

-- No

What is the non loaded rpm limit?

-- Do you mean with the shifter in neutral? I didn't think you were supposed to do that.

Have the tachs been verified and/or strobed?

-- No, I'll add that to the Earl list for fall

Do you have pyro's or boost gages on the engines- what do they read at WOT?

-- No

Are you in fresh water?

-- Semi, upper part of the Chesapeake Bay

[smitty477]

Hello Foster - out crusiing with some limited internet right now.

When was the last time the props were scanned and/or inspected?

-- Never that I know of. When it was out of the water in July I looked at them for dings and bends, nothing visible.

They can be pretty far off from what you may think they are if not confirmed. Did the boat 'act' any different during its lifetime with you?

Can you get the rpm's above 3,000 in any trim condition?

-- No

OK - so this is one place where there is a bit of an issue - large or small no way to tell yet.

Tachs good, cables fully open, fuel pump limiters adjusted, intercoolers clean, turbos making psi, pump timing good too many possibilities to guess.

What is the non loaded rpm limit?

-- Do you mean with the shifter in neutral? I didn't think you were supposed to do that.

This is a common test with a warmed up diesel. Slowly increase & decrease rpm's to max for a few seconds only and record the number. If tachs are accurate and all else is well it should read 3,250-3,300. So then in gear at WOT testing it should read near 3,100+ a bit.

Have the tachs been verified and/or strobed?

-- No, I'll add that to the Earl list for fall

If Earl will be there you have the best answer of all, perhaps write your questions down now as they can escape you when you are at the boat.

Do you have pyro's or boost gages on the engines- what do they read at WOT?

-- No

Earl can read your boost pressures at time of visit.

Are you in fresh water?

-- Semi, upper part of the Chesapeake Bay

That answers part of your question - the boat will always be slower in fresh water.

Hope this helps

[Foster]

On the way back I tried the no load test since the engines were warm. Port WOT 3300, Stb=3400. But the port engine stumbled on acceleration, while the stb went smoothly to 3400.

I'll add the info to the "Earl Folder" for his analysis.

Thanks!