4200 SCR lacking full power - Maxum Boat Owners Club

CaptGreg · 07-25-2018, 03:49 AM

2002 4200 SCR. I've had the running gear worked on and two new DQX 22x25x2 props installed (originals were Nakashimas). At full throttle my starboard is at 2800 rpm and my port is at 2450 rpm but the boat is only doing 18 knots in calm seas. Cummins gave me a thumbs up on the engines (450Cs 3000rpm at engine) and now its dry docked waiting for a genius to figure out what happened. I've been told the starboard shaft strut is bent but its not confirmed yet but would explain a zero tach at gear forward/reverse because the shaft is difficult to hand turn. The boat gets up quick but fails to go beyond 18 knots. Both shafts were straightened 4 months ago and the shafts were aligned at that time. Any ideas?

mmwjr · 07-25-2018, 10:42 AM

If the shaft is bent there should be a vibration when in gear. If they were just straightened 4 months ago and it is now bent is the alignment correct? Are the cutlass bearings good? Did you hit anything?

shrew · 07-25-2018, 02:32 PM

I would assume if both shafts were straightened, then a grounding occurred. The other cause might be an improperly placed lifting strap on a travel lift during a haul out.

CaptGreg · 08-13-2018, 07:02 PM

Mike.....I had the shafts straightened, props balances and checked for specs, cutlass bearings changed, and even the starboard strut was repositioned a few millimeters. It was out of the water for three weeks being worked on (I pamper her) and the moment I took her sea, the same results.....nothing had changed. I've done everything I can except change my NEW DQX props back to new Nakashima props. I'm trying to verify that Maxum used Nakashima's in the build.

CaptGreg · 08-13-2018, 07:04 PM

Shrew.......no groundings but the "lift" is an idea. Only thing is that after having the issue, I had it hauled out again and the shaft was fine but upon being returned to water, I still had the problem.

mmwjr · 08-13-2018, 09:41 PM

When did it last run correctly? What has changed since then, props? Are these news props the same number of blades and pitch?

CaptGreg · 08-14-2018, 02:57 AM

Quote:

Originally Posted by mmwjr

When did it last run correctly? What has changed since then, props? Are these news props the same number of blades and pitch?

I know what you're thinking and if thats the problem I'll be so pissed. After the Nakashima's were replaced (starboard blade sheered off at the hub) with new DQX's under the same specs 22" x 25 pitch x 2" bore Nibral (same specs) I began to notice the difference. In the last week of July I had the props removed and specs checked/confirmed. Identical! Aren't blades supposed to be interchangeable as long as the specs are identical? I can't get Nakashima in Japan to respond to inquiries and Michigan Wheel wants all kinds of boat info before they'll comment.

Why didn't I replace the old props with the same manufacturer? It's a long story about a screw-up at the boatyard.

mmwjr · 08-14-2018, 03:16 AM

Understand stuff happens but it sounds the the prop change is when the performance was impacted so that’s were I would focus. Does the new ones have the same number of blades as the old ones? What about weight, different materials may have the new ones weighing more.

shrew · 08-14-2018, 02:44 PM

Quote:

Originally Posted by CaptGreg

I've had the running gear worked on and two new DQX 22x25x2 props installed (originals were Nakashimas). At full throttle my starboard is at 2800 rpm and my port is at 2450 rpm

Quote:

Originally Posted by mmwjr

but it sounds the the prop change is when the performance was impacted so that’s were I would focus. Does the new ones have the same number of blades as the old ones? What about weight, different materials may have the new ones weighing more.

If it were the props, wouldn't you expect both sides to be at 2450? What is the max RPM for the engines? Does Stbd reach that RPM?

CaptGreg · 08-15-2018, 12:19 AM

Just had the running gear guy here today and the starboard shaft spins more loose but it's still weaker than the port.....example.....from a stopped position, port forward and starboard back......then port back and starboard forward. This should spin the boat without much varying from the circle however the starboard shaft feel weaker such that the port pushes and pulls stronger taking the boat out of the tight circle. The full throttle test had identical results of port 2600 rpm and starboard 2750 but the top speed was 18.5 knots.....no change. The WOT is 3000 rpm at 28 - 29 knots......supposed to be. I'm working with Michigan Wheel to analyze the current DQX props and the alleged original Nakashima props with the engine and transmission specs. Waiting for my mechanic to retest the rpm at the engine with no load. I like a good mystery but this has been crazy. Props alone shouldn't be able to cause a 10 knot drop in performance, right?

mmwjr · 08-15-2018, 03:12 AM

Quote:

Originally Posted by shrew

If it were the props, wouldn't you expect both sides to be at 2450? What is the max RPM for the engines? Does Stbd reach that RPM?

Yes if the props were matched. New props and the issues started so I suspect one or both is not right. If not matched you can get what he is observing.

mmwjr · 08-15-2018, 03:14 AM

Quote:

Originally Posted by CaptGreg

Just had the running gear guy here today and the starboard shaft spins more loose but it's still weaker than the port.....example.....from a stopped position, port forward and starboard back......then port back and starboard forward. This should spin the boat without much varying from the circle however the starboard shaft feel weaker such that the port pushes and pulls stronger taking the boat out of the tight circle. The full throttle test had identical results of port 2600 rpm and starboard 2750 but the top speed was 18.5 knots.....no change. The WOT is 3000 rpm at 28 - 29 knots......supposed to be. I'm working with Michigan Wheel to analyze the current DQX props and the alleged original Nakashima props with the engine and transmission specs. Waiting for my mechanic to retest the rpm at the engine with no load. I like a good mystery but this has been crazy. Props alone shouldn't be able to cause a 10 knot drop in performance, right?

Just proves what you already know, one side is producing more thrust than the other. Still don’t know why.

MoonRiver · 08-15-2018, 05:17 AM

So this may sound crazy but I'm wondering if the DQX and Nakaimasi propellers are of different strength material. Maybe the DQX is flexing under the torq of the engine. Another thought might be the proper pitch of the port & strbd props. If the port was not tuned to the strbd, maybe?

jparsons121 · 08-16-2018, 02:09 PM

Sounds like you're narrowing in on the issues like Mike said originally.
The only major change that would affect performance is the replacement props (barring a coincidental issue with the mains/trans/etc)

Shaft runout would primarily cause vibration, not rob any noticeable amount of power. With the info provided, I'm with Mike, suspecting that the props aren't the same pitch/cup/etc.
Material flex is a factor considered in max performance prop tuning/selection, but wouldn't account for the losses you describe.

John

Bmahoney2016 · 09-04-2018, 02:20 PM

Good morning. Just joined the club. Have a 2006 4200. Spun the Port shaft of and lost prop couple weeks ago. Prop guy trying to match the starboard prop and had given me the nakashima(?) story for this model but is having trouble getting a replacement. I want to just replace both props and move on. Anyone know exact what specs to be looking for to for this boat??

shrew · 09-04-2018, 02:35 PM

What is the "Nakashima Story"?

Bmahoney2016 · 09-04-2018, 02:55 PM

Starboard prop I still have had no markings on it. Had to research the fact that Maxum used nakashima props to even know where to look for replacement. Tried to order one and it was wrong so trying again. I was contemplating a spare set anyway before this issue so either way I want to buy new ones but don't know what to get

CaptGreg · 09-18-2018, 01:33 AM

Bmahoney2016........WELCOME! Good to have another 4200SCR capt. After eliminating many contributory causes to power loss, I've decided to purchase two new props. My current props are DQX 22x25x2 x 4 inch hub length. These were purchased based on the recommendation of a boatyard. I'll never listen to anyone again without triple checking their information. Through my research I've found that the original propellers chosen by Maxum for our specific boat (4200 SCR) was the Nakashima 23 inch 25 pitch 2 inch diameter with a tapered 6 inch hub..........substantially different than what I was recommended. I found some really nice people on the west coast who have told me they can get the OEM props from Nakashima but the wait time will be 6 to 8 weeks. The cost is cheaper than the DQX at just under $2000 per prop. My desk is a mess but I'll be posting the name & tele of the company who can provide the OEM props with the contact name at the company within the next couple days. I'm changing the Starboard injectors this week and provided the sea trial indicates the same lower performance, I'll be ordering the new OEM Nakashimas. The Florida Keys and Caribbean islands are calling but 18.5 knots just isn't enough to run on my schedule. I'll be posting later. Wish me luck.

CaptGreg · 09-20-2018, 01:37 AM

Hey all.......anyone wishing to find the OEM props for the 4200 SCR which were 23"x25x2x6"hub length can get them from Nakashima via Josh who works with Sea Ray. He's on the NorthWest coast at 206-933-2473. Very helpful guy and the pricing is good. I'm still waiting to complete just a little more engine work and discussion with a prop shop about this issue before I make the call to order new props.

CaptGreg · 12-28-2019, 04:13 AM

I've been absent from this forum for a long while. There's nothing that can't be fixed if you have enough time and money to throw at the problem. My boat is awesome and running great almost like new. Top speed would be a little faster had the prop shop known the original specs which were Nakashima 4x"26" nibral not 25, with med cup and 6"hub. Anyway....I've only lost 2 or 3 knots top end. Both Cummins are running well and very economical. My only complaint is I wished I'd bought a 25 kg Rocna rather than the 20 kg.
I'll be a grandfather soon and moving so I must sell my boat which is finally awesome after I've spent over $200,000 in the past 3 years. It sucks that I'll lose all that time and money but if anyone is interested, she's listed in yacht world .