WTH do I do with this?

[ageless]

My 55c was missing 200-250 RPM's under load, heavy soot on
transom and the horizon. Had props pulled, shop calls to inform the port wheel is 27x28, the starboard 27x30. I did note the starboard was slower to accelerate, by tach, but at wide open port was 2100, starboard 2150. Recommendations on where to go with these

 

[krush]

take both to 27x29 ?

 

[doc g]

didn't you just buy this boat?? ....and talk to a prop shop and other 55C owners before changing anything . I would think you need to get rid of pitch on both to get 2350 rpm. I thought each inch = about 50- 100 rpm at WOT?? .....Pat

 

[ageless]

didn't you just buy this boat?? ....and talk to a prop shop and other 55C owners before changing anything . I would think you need to get rid of pitch on both to get 2350 rpm. I thought each inch = about 50- 100 rpm at WOT?? .....Pat

they are at the shop, they discovered the difference. It's just weird that the 27x28 only reached 2100, the 27x30 2150, the bigger prop spun up higher

 

[Avenger]

Did you verify that your tachs are accurate?

 

[racclarkson@gmail.com]

My 55c was missing 200-250 RPM's under load, heavy soot on
transom and the horizon. Had props pulled, shop calls to inform the port wheel is 27x28, the starboard 27x30. I did note the starboard was slower to accelerate, by tach, but at wide open port was 2100, starboard 2150. Recommendations on where to go with these

You using a really good prop shop? A good prop guy has forgot more than we'll ever know. If you're not sure, put the job on hold until you have confidence in them or find someone else. I grabbed my props away from the best guy around in Ft. Meyers when I found out he was the best guy around on outboard props. The boatyard made a recommendation on what was in their best interest and not mine.

Don't worry too much about other 55's. Tell the prop shop what your expectations are relative your concerns. Ask them if they think they can achieve the goals. Settle on an agreed upon level, and ask what happens if the performance falls short.

The minute you tell them how you want your props pitched or balanced or cupped is the point where you absolve them of any responsibility other than doing exactly what you told them to do.

 

[doc g]

If that's so I would suspect engine issues, the "under"- propped side could be pulling the "over"- propped side down(rpm -wise) too, why would you not have the same props on both sides????

 

[Bob Bradley]

The fact that the bigger prop spun higher makes me think it might be more than just unmatched props that is causing your soot and lost rpms. Have you verified that all your injectors are firing? Are the airseps (if so equipped) clean and supplying air? Might you have a turbo outlet tube that is leaking past a hose? Is it aftercooled, and if so, is the aftercooler clean?

I'd hate to see you change the pitch of the props and reinstall them on improperly running engines. Big waste of fuel and efficiency (speed).

 

[ageless]

Did you verify that your tachs are accurate?

supposedly confirmed with photo tach during survey

You using a really good prop shop? A good prop guy has forgot more than we'll ever know. If you're not sure, put the job on hold until you have confidence in them or find someone else. I grabbed my props away from the best guy around in Ft. Meyers when I found out he was the best guy around on outboard props. The boatyard made a recommendation on what was in their best interest and not mine.

Don't worry too much about other 55's. Tell the prop shop what your expectations are relative your concerns. Ask them if they think they can achieve the goals. Settle on an agreed upon level, and ask what happens if the performance falls short.

The minute you tell them how you want your props pitched or balanced or cupped is the point where you absolve them of any responsibility other than doing exactly what you told them to do.

The shop I'm using was chosen after personal research and interviewing. They have props that are 6' in diameter, do all the work for the port in Wilmington. He mentioned one prop may be pulling the other down, they had a small amount of scale build up to remove and would work them to match. All I have told them is I need 200-250 RPM's, we'll see how things go when I call in AM

If that's so I would suspect engine issues, the "under"- propped side could be pulling the "over"- propped side down(rpm -wise) too, why would you not have the same props on both sides????

Prop shop mentioned one pulling the other down, good question why they're different, not happy that my survey says "reported 27x29"

The fact that the bigger prop spun higher makes me think it might be more than just unmatched props that is causing your soot and lost rpms. Have you verified that all your injectors are firing? Are the airseps (if so equipped) clean and supplying air? Might you have a turbo outlet tube that is leaking past a hose? Is it aftercooled, and if so, is the aftercooler clean?

I'd hate to see you change the pitch of the props and reinstall them on improperly running engines. Big waste of fuel and efficiency (speed).

The prop work is being done based on recommendation from survey. I have not been into the injectors, airseps were cleaned in April, motor is intercooled

 

[Cricket]

I would have the engines gone through before having the wheels modified. Did you have an engine survey done? If yes was it a DD guy or survey guy? April doesn't really mean anything, how many hours since cleaning, same for the fuel filters, etc.

 

[Avenger]

Agree, a baseline is in order. Unknown history, mismatched components and questionable data,... the acronym GIGO comes to mind. The whole thing needs to be looked at from square one.

 

[mykim]

My 55c was missing 200-250 RPM's under load, heavy soot on
transom and the horizon. Had props pulled, shop calls to inform the port wheel is 27x28, the starboard 27x30. I did note the starboard was slower to accelerate, by tach, but at wide open port was 2100, starboard 2150. Recommendations on where to go with these

First off. 55C's came from the factory with 32" wheels. So the mystery deepens as to why your WOT RPMS are low.
What HP are your 1271's? How many hours on them? Do you know when was the last time the timing was set and the racks adjusted? Lots of things play into low RPM's other than the props.

 

[racclarkson@gmail.com]

First off. 55C's came from the factory with 32" wheels. So the mystery deepens as to why your WOT RPMS are low.What HP are your 1271's? How many hours on them? Do you know when was the last time the timing was set and the racks adjusted? Lots of things play into low RPM's other than the props.

Deeper still. My owner's manual shows 30" props. I believe majority of the 55s were, as you say, 32" with Allison 2:1 gears adverting 650HP. Mine is ZF 1:1.51 with original rating of 850HP. There's at least some justification for Ageless' 28" wheels. PO of mine left me with a set of 28s. Said it jumped up on plane but lacked the top end of the 30s by a knot. Loooots of variables. Anyone looking for a nice set of balanced 28 X 28s?

 

[ageless]

I would have the engines gone through before having the wheels modified. Did you have an engine survey done? If yes was it a DD guy or survey guy? April doesn't really mean anything, how many hours since cleaning, same for the fuel filters, etc.

did not have an engine survey, based on the extensive maintenance records provided and the engines performance during survey (minus the 200 RPM's under load) I was confident in their condition.
the vessel had 15 hours on it in 3 years, the fuel filters have 20 hours max on them, bowls look clean

 

[ageless]

Unknown history, mismatched components and questionable data,... the acronym GIGO comes to mind. The whole thing needs to be looked at from square one.

what history are you referring to?

what questionable data?

little early to jump to an unreasonable conclusion such as GIGO, wouldn't you say? Or would you like to clarify where the unjustified statement derived?

 

[ageless]

First off. 55C's came from the factory with 32" wheels. So the mystery deepens as to why your WOT RPMS are low.
What HP are your 1271's? How many hours on them? Do you know when was the last time the timing was set and the racks adjusted? Lots of things play into low RPM's other than the props.

my manual reflects 30" wheels from the factory, which are likely the extras in the ER.

1271's are 850hp, ZF 1.51:1, 1500 hours, 2012 on timing and racks

I agree with the other factors, thought I was being guided by a knowledgable individual

 

[ageless]

I'm thinking a call into Hatteras may be in order to clarify the wheels

 

[jim rosenthal]

I hate to say this is interesting, because the last thing you want to have is an "interesting" problem. Interesting usually equates to expensive.

But I agree with those who feel you should zero out the engine variables, if that's the right term, before looking at the wheels. The problem is that there are so many other potential causes of this kind of odd behavior on the part of the boat.

It seems to me that you can make a pretty good argument for the idea that the power curves or output differs a lot from one engine to the other. Unfortunately, putting your engines on a dyno to check what they are really doing is impossible.

But you might be able to get close by seeing what the high idle is on each one, verifying that the racks are opening all the way, and that all cylinders are firing reliably. Also that you don't have excess frictional losses anywhere in either driveline (bad cutlass bearings, etc) and that the props scan to the reported measurements accurately. I assume both gears are the same ratio- a friend of mine chased unequal power and fuel use for years only to finally figure out that he had two different gear ratios P&S- he wasn't happy to say the least.

Good luck on this. I hope you're able to get to the bottom of it. No pun intended.

 

[ageless]

I hate to say this is interesting, because the last thing you want to have is an "interesting" problem. Interesting usually equates to expensive.

But I agree with those who feel you should zero out the engine variables, if that's the right term, before looking at the wheels. The problem is that there are so many other potential causes of this kind of odd behavior on the part of the boat.

It seems to me that you can make a pretty good argument for the idea that the power curves or output differs a lot from one engine to the other. Unfortunately, putting your engines on a dyno to check what they are really doing is impossible.

But you might be able to get close by seeing what the high idle is on each one, verifying that the racks are opening all the way, and that all cylinders are firing reliably. Also that you don't have excess frictional losses anywhere in either driveline (bad cutlass bearings, etc) and that the props scan to the reported measurements accurately. I assume both gears are the same ratio- a friend of mine chased unequal power and fuel use for years only to finally figure out that he had two different gear ratios P&S- he wasn't happy to say the least.

Good luck on this. I hope you're able to get to the bottom of it. No pun intended.

I intend to do just this Jim, will dive into the injectors and rack this weekend. If there was an issue within either of these would it present itself only under load?
Without tearing into the gears, I'm ASSuming the only way I can verify ratios is by the plates on the side and they both DO reflect 1.51:1. The vessel is on the hard and I didn't detect any play in the shafts before removing the wheels, had planned to put a dial indicator on them this weekend prior to this prop finding.

 

[dsharp]

There's no standard wheel for any particular model boat. The only thing that you should worry about is the engines being able to reach it's rated rpm under load. Have the wheels made the same at the lower pitch and see what it turns. See if the yard will haul at a reduced rate if you need to fine tune the pitch. There's no way to know what going to happen until you make a change then go run the boat. A full tower will make a substantial change in prop size