new prop for 28 te

[saltshaker28]

I am running a 19by 18 prop I got from h&h props it is ok but I am burning more fuel than I was with the prop that came with the boat the reason for the change in the prop was Mack boring said the 19 by19 was lugging the motor Has anyone had a 19 by19 worked and if so who did it and how were the results

[Capt Paul]

I went through some prop rework/replacement last year. What ever prop you use the one thing everyone has told me and what I learned is that you need to make sure that you can obtain WOT RPM for the motor/tansmisson combination. From your desritption its sounds like MAC Boring is saying that this is not happening with your old prop. So even if others got it to work , make sure they have the same engine and transmission ratio that you have. I had mine scanned using 'PROPSCAN" and tuned to make sure it met spec. Picked up an extra knot at the same RPM.

What engine do you have? I have a 6LP-STE 300HP rated at 3800 RPM WOT. I use a 17X19 prop.

It makes sense to me that you are using more fuel to go the same speed with less pitch in your prop.

Paul

[RobS]

I am running a 19by 18 prop I got from h&h props it is ok but I am burning more fuel than I was with the prop that came with the boat the reason for the change in the prop was Mack boring said the 19 by19 was lugging the motor Has anyone had a 19 by19 worked and if so who did it and how were the results

Where are you located. There is an excellent prop shop here on Long Island? Bossler & Sweezey (631) 286.0458. They have recon'd all props on my prior boats including my 28TE. This winter I will be re-working the prop slightly to achieve another 100-150rpms WOT.

A prop can be worked to add or remove a full inch of pitch. So your 19x19 should have been able to be reworked to match the specs of the 19x18. What is the cup in each prop and what are your WOT and speed specs with each? I believe H&H recommended a 5 cup in the 19x18.

[saltshaker28]

I live on Long Island and I do not know that much about props but I do know when I was running the 19by 19 spec for a 315 Yammar wot was 3800 and that is exactly what I used to get now with the 19 by18 wot is 4000 what should I do

[RobS]

I live on Long Island and I do not know that much about props but I do know when I was running the 19by 19 spec for a 315 Yammar wot was 3800 and that is exactly what I used to get now with the 19 by18 wot is 4000 what should I do

Have you verified the accuracy of your tach? If you have a Yanmar tach it is safe to assume it is wrong, they basically all are. Usually they read 100 to 150 rpms too high but you must get it checked with a photo tach to know.

The desired rpm is 3900 at Full Load - Full Fuel, Water & Gear. But until you know the accuracy of your tach you can't do anything.

Assuming your tach is accurate (doubtful, but for matter of discussion) , based on the numbers you have provided, you need to split the difference btwn the two props. So adding a half inch of pitch to the 19x18 or removing a half inch of pitch from the 19x19 should accomplish this. If you were to leave it alone, you should stay with the 19x18 as it's better to be at 4000 WOT than 3800.

How was your speed and fuel cosumption effected btwn the two props?

[Mariner]

You know what they say about people who tinker with their props; they keep the mechanic's kids in new clothes.

[RobS]

You know what they say about people who tinker with their props; they keep the mechanic's kids in new clothes.

That only applies to those trying to gain speed and disregard proper rpm's, engine loading concerns, etc...

[saltshaker28]

Thanks for the info looks like I need to find a phototach and find out my true wot before Ithink about the prop

[zinbaad]

Glad I am reading these posts. I am probably going to do the same adjustments. Sea trialed last week & wot was 3700 & 36oo on the port Yanmar.. Survey is a go Thursday and we will see what happens when the hull is lifted & pressure washed. Hopefully both engines on the 31 TE goes right up to 3800 or am I looking for 3900?? Gonna be a bit widy out there for sure

[dowdster]

I have a 1999 Albin that originally had the 300hp Yanmar. It just got repowered with a new 2008 Yanmar 6LPA 315 by the previous owner. He kept the original prop. Now, with a clean bottom, I can get 4150 RPM's (according to the dash tach). I'm wondering if I should add slightly more pitch to the prop to account for the slight increase in power. Also, the prop has a few small pits on the edges. Is this something that can be machined by a prop guy or am I looking at a new prop?

[zinbaad]

When I picked up my albin port was running to 3600 & starboard to 3800. I was told was correct max at 3800. I wondered if I was dragging a plastic bag or had a chipped prop stopping me from wot. After taking her home and cleaning the air filters both engines came to WOT, I was relieved. but I do try to take the advice runnng both motors more than 20% under WOT around 3200. Ouch 4150 sound a bit too much, better check the tachs

[RicM]

Yes, do not make ANY decisions based on the installed tachs. You need someone who knows what they are doing, with a digital photo tach, to check the accuracy of the dash tach at the speed in question. There are many reports of dash tachs being off 200-300 RPM. Takes 2 people to safely do this. Underproping will not really hurt anything except some fuel economy. Overproping can burn out your motor. Here's the bad news. The 300HP Yanmar is the same engine as the 315, but with the new valve guides and valves, they achieved the the extra 15 hp by futzing with the specs. See www.boatdiesel.com for extensive discussions on all these topics. It's perfectly possible the prop you have is fine.

[halfmoon]

My "new" 2001 28TE has Yanmar 300 with 19x19 four blade prop. By photo tach I get WOT 3705 rpm and 20 mph. Experienced local Yanmar rep/mechanic says, according to Mack Boring, WOT should be 4000 rpm, not the 3800 as labeled on the engine. So, I'm 300 rpm low. So, do I start tweaking the 19x19 or go ahead and move to smaller prop. Another member has posted 27.5 mph with a 17x17.5 prop.

[RicM]

27.5 mph or 24 knots is pretty high on the scale for a 28 TE unless it is brand new, straight from the dealer, with almost empty tanks and a skinny captain. Comparing speed is not really relevant to the issue anyway, you could crank up the prop pitch and gain more speed but burn out your engine in the process. You are looking for the sweet spot where fuel economy, engine life, and speed come together on the chart. RPM is your indicator, not your goal. If you cannot turn the rated RPM at WOT then you are over propped for the weight, condition, and trim of the boat and your engine life will be shortened. If you are under propped, you will not get full fuel economy and speed. I'd rather be on the slightly under side, as fuel (believe it or not) is cheaper than Yanmars. You are not that far off. Take it to a Prop Scan shop and tell them you want 150-200 more RPM. He won't let you watch them adjust it, because they just hit with a big hammer until it reads right on the scanner. It's not a science, it's an art, you'll be closer to the ball park, but close enough. Remember your boat can vary 1000 pounds by fuel & water load alone. Going to another prop size means you'll be starting at square one, so you'll have the cost of prop PLUS the adjustment or two to get it right.