Boat test 2000 260 DA, 7.4L will not achieve max RPM

[Theresamarie11]

Hi all, I did a boat test on a 2000 sundancer with 7.4L MPI motor, and bravo 3 drive with 24p bravo3 prop. 200hours on the motor and you could eat off of it (really).

When testing the boat, it shudders when under acceleration and smoothes out as it comes up to speed. The shuddering isn't violent but it is noticable to both driver and passengers. While crusing (constant speed) you can't tell that it's shuddering at all.

The thing is that it will only hit around 38.6mph on the GPS at 4000 RPM. This would correspond to a 15% slip which seems reasonable. Couldn't get it past 4K RPM.

At first I thought it might be over propped, but in checking the sea ray prop guide it says the 260 with 7.4L and bravo3 has a 2.0 gear ratio and the prop should be a 24p. So all sounds right here.

The owner, and other owners on this site say it should hit 45mph. The boat was very lighly loaded. 1/2 tank fuel, no water, or anything in the holding tank and no other equip.

The bottom is epoxied instead of painted (so very smooth) and blemish free. There is some kind of dried growth on the bottom but it's very slight and very thin and isn't everywhere.

1/2 of the fuel in the boat was from when it was buttoned up last year. It hasn't been run since it was winterized in 08 until this past Friday. Would bad fuel cause the shuddering on acceleration and low top WOT RPM.

The lake had a slight chop and we tried both into, and with the wind (no difference whatsoever).

There seemed to be no play in the drive (back/forth).

Everything else seems to be ok.

I posted a question in the cruisers forum but thought maybe I might be able to get some other answers here as well.

Thanks for any help you can provide.

What should I have my mechanic check, thoughts?

Other thoughts, from cruiser forum and myself, besides bad gas that would cause the shudder as well as lack of top RPM:

shift cable/acceleration cable misadjusted (??)
Lost a cylinder (wire,plug,distributor,compression)?
- what would this feel like?
lack of timing advance?
Some kind of ECU issue??
Dirty intake (this seems unlikely)



Terri

 

[bushway9172]

Have you already purchased this boat? If not, try out the '04 that you were debating between, and see if you see a difference. Upon acceleration, were the drives trimmed all the way down? Once on plane, did you trim the drives up a bit to reduce drag (this will easily add 3-4mph). Also, you talk about the dried up gunk... that could also have something to do with not obtaining max. speed (surprisingly could lose anywhere from 2-10 mph because of this, but of course it depends on the amount... I underestimated the barnacles on my outdrive and trim tabs.. and it's slowing us down quite a bit.. almost 10 mph). I don't think this is as big of a problem as you may be anticipating... possibly just a few driving adjustments. Anyway, let me know! Trying to help you :thumbsup:

Brandon

 

[Theresamarie11]

Have you already purchased this boat? If not, try out the '04 that you were debating between, and see if you see a difference. Upon acceleration, were the drives trimmed all the way down? Once on plane, did you trim the drives up a bit to reduce drag (this will easily add 3-4mph). Also, you talk about the dried up gunk... that could also have something to do with not obtaining max. speed (surprisingly could lose anywhere from 2-10 mph because of this, but of course it depends on the amount... I underestimated the barnacles on my outdrive and trim tabs.. and it's slowing us down quite a bit.. almost 10 mph). I don't think this is as big of a problem as you may be anticipating... possibly just a few driving adjustments. Anyway, let me know! Trying to help you :thumbsup:

Brandon

Hi Brandon, thank you for the comments, they are highly appreciated. We haven't purchased the boat yet (being checked out this week) and did try to test drive the '04 today but the person wasn't around.
This is our 3rd boat so we're pretty familiar with trimmiing for optimum speed, but not familiar with tabs. So I put tabs up entirely which most seem to say is best for WOT runs for top speed.
We can check cleaning the bottom, but there's not much there. I would be surprised if this is slowing us down.
It's nothing like barnacles or mussels or anything even remotely close to that kind of issue (drive is clean as well and props look good).. just some stringly stuff on parts of the bottom (very very thin and flat to hull and not a lot of it).

The broker left the camper top up, but took out front vinyl windws and aft cavas. So just the sides and bimini were up. Since my current boat doesn't see any loss of speed for the Bimini being up, I am expecting this boat would not see significant drag either.

I hope we figure this out really soon, as I accepted an offer on our other boat... so if this doesn't pan out, I'll be 'boat-less' :wow:


Terri

 

[bushway9172]

Hi Brandon, thank you for the comments, they are highly appreciated. We haven't purchased the boat yet (being checked out this week) and did try to test drive the '04 today but the person wasn't around.
This is our 3rd boat so we're pretty familiar with trimmiing for optimum speed, but not familiar with tabs. So I put tabs up entirely which most seem to say is best for WOT runs for top speed.
We can check cleaning the bottom, but there's not much there. I would be surprised if this is slowing us down.
It's nothing like barnacles or mussels or anything even remotely close to that kind of issue (drive is clean as well and props look good).. just some stringly stuff on parts of the bottom (very very thin and flat to hull and not a lot of it).

The broker left the camper top up, but took out front vinyl windws and aft cavas. So just the sides and bimini were up. Since my current boat doesn't see any loss of speed for the Bimini being up, I am expecting this boat would not see significant drag either.

I hope we figure this out really soon, as I accepted an offer on our other boat... so if this doesn't pan out, I'll be 'boat-less' :wow:


Terri

Terri, we purchased our 270 SLX brand new in April, and it already has a significant amount of crap on the bottom, which is definitely a bummer. :smt009 We were new to the tabs also, after upgrading from a 220 Sundeck. If you hold the tabs down so that the bow is up (tabs are also up), that is how to obtain maximum speed. It was a little confusing to me at first, but once you get out there on a good day, it's so easy to feel things out. You stated that you are aware of trimming to get optimum speed out of the boat... which is good; however, I noticed that with a bigger boat, you can trim up a little bit more, without cavitation of the props. In my 220 SD, I'd only trim up 1 or 2 notches (out of 10). In the 270 SLX, I trim up to 4 or 5 notches (also out of 10). Just a quick note. :thumbsup:

Anyway, the mechanic for our boat said the reason WE aren't obtaining max RPMs or max speed is because of the crap on the outdrive :smt009 which really stinks since the boat is only a few months old. It's only going 42-45mph WOT, instead of the expected ~55mph. Hopefully we can have the boat hauled out soon to have them scrape/powerwash.

Also, the bimini itself should not create much, if any, drag, considering the already deep design of the boat; although the boat DOES have the arch option, right? If so, this may add some extra weight.

 

[Theresamarie11]

Terri, we purchased our 270 SLX brand new in April, and it already has a significant amount of crap on the bottom, which is definitely a bummer. :smt009 We were new to the tabs also, after upgrading from a 220 Sundeck. If you hold the tabs down so that the bow is up (tabs are also up), that is how to obtain maximum speed. It was a little confusing to me at first, but once you get out there on a good day, it's so easy to feel things out. You stated that you are aware of trimming to get optimum speed out of the boat... which is good; however, I noticed that with a bigger boat, you can trim up a little bit more, without cavitation of the props. In my 220 SD, I'd only trim up 1 or 2 notches (out of 10). In the 270 SLX, I trim up to 4 or 5 notches (also out of 10). Just a quick note. :thumbsup:

Anyway, the mechanic for our boat said the reason WE aren't obtaining max RPMs or max speed is because of the crap on the outdrive :smt009 which really stinks since the boat is only a few months old. It's only going 42-45mph WOT, instead of the expected ~55mph. Hopefully we can have the boat hauled out soon to have them scrape/powerwash.

Also, the bimini itself should not create much, if any, drag, considering the already deep design of the boat; although the boat DOES have the arch option, right? If so, this may add some extra weight.

Thanks for response.
Loosing 10 MPH seems like a lot so you must have a huge amount of stuff on the bottom. I think we're loosing 6 or so MPH and we do have some stuff on the bottom, but since I have never kept a boat in the water, I don't know to equate the bottom condition to a performance decrease. Seems drastic to me. In any case, since I know folks who have similar boats, with same motor/prop combination, and the prop is the one recommended by Sea ray, there has to be something we haven't found yet.

Terri

 

[bushway9172]

Thanks for response.
Loosing 10 MPH seems like a lot so you must have a huge amount of stuff on the bottom. I think we're loosing 6 or so MPH and we do have some stuff on the bottom, but since I have never kept a boat in the water, I don't know to equate the bottom condition to a performance decrease. Seems drastic to me. In any case, since I know folks who have similar boats, with same motor/prop combination, and the prop is the one recommended by Sea ray, there has to be something we haven't found yet.

Terri

Drastic is definitely the right word. Sadly, the cause of the problem has been verified by multiple mechanics, and it surely is the crap on the hull/outdrive/trim tabs. :smt013

I learned not to underestimate what seemed like not-too-much "crap" or barnacles. Apparently, a little bit of gunk causes a noticeable difference, and because of the low-profile, sleek design of our boat, it makes the boat significantly more "sluggish."

 

[Theresamarie11]

Latest news (hope someone smart is watching).

Compression test on all cylinders is good.

Since I also felt some vibration, they also removed the drive and checked all bearings, I watched as they did this and also removed the drain plug (no shavings at all, not even a little). Although the oil smelled burnt (no sparkles) and it hasn't been used all year except for our short run. So it appears it wasn't changed for winterization at end of '08, which i have to inquire about.

No water/corrosion inside, anywhere. Things look almost new inside.

Prop is perfect (looks new). Some corrosion around prop shaft bearing carrier but mechanic said normal, just surface and no pitting. He's going to sand, prime and paint it.

There is a little bit of bottom stuff, but boat dealership owner said that'll make little difference.

I guess we go on to fuel and ignition systems.




Terri

 

[jadams2009]

I am experiencing similar performance issues with my newly purchased used 1999 Sundancer 270, equipped with 7.4L MPI, Bravo III with 24p props. Bottom is painted and clean. 400 hours on the engine, oil pressure psi and engine temperature is all good.

Engine runs smoothly, however I only achieve 4100 RPM resulting in 36MPH (GPS measured). This is with the trim tabs up and the drive slightly raised - which adds 200+ RPM and 1-2 MPH. This was last weekend with 75 gallons (holds 100) of gas, 25 gallons of water, 8 gallons in holding tank and 350 lbs of passenger weight.

Over the past several weeks, I had been experiencing degraded performance - which turned out to be a bad spark plug wire (#7). This was causing my inability to get up on a plane. Having the tabs down was too much resistance on the engine which was only firing 7 of the 8 cylinders. This was fixed - so this got me back to the baseline performance figures stated above.

So, here is what I have done to troubleshoot (so far):
- Changed engine oil and filter
- Changed plugs and wires (old plugs were NOT fouled)
- Checked engine compression (all between 130 - 140 psi)
- Changed spin-on fuel/water separator filter
- Checked fuel pressure on the rail (consistent 38-40psi through RPM range)
- New gas
- Injector cleaner (fuel additive)
- Checked distributor cap and rotor (clean)
- Cleaned intake
- Cleaned Flame Arrestor

I believe the boat should hit 40MPH, but not sure - does anyone out there have the 1999 270 hull with this setup. Mine is NOT the SE model. What should I expect?

What I will likely follow up on:
- Checking the timing - i.e. the timing advance
- Checking the cleanliness of the IAC, replace
- Testing the Throttle position sensor (TPS)

ANY OTHER IDEAS?

Thanks,
Jeff

'99 Sundancer 270 7.4L MPI Bravo III
'99 Bayliner Capri 2052 4.3L Alpha

 

[boatrboy]

I believe the boat should hit 40MPH, but not sure - does anyone out there have the 1999 270 hull with this setup. Mine is NOT the SE model. What should I expect?

We have the same boat, I do not have a/c or genny. Last week I hit 41 mph at about 4400 rpm w/full gas, solo ride, half grey water and half water. I have 22p props. I cruise around 27 mph at about 3450 rpm. getting about 1.8 mpg.
Hope this helps.

Mark

 

[jadams2009]

Well, maybe I need a prop change to 22p. I was going to have the props reworked over winter, but...

Mark - do you know if your props were original? SeaRay's prop chart for '99 lists our configuration with 24p and a WOT of 4600.

Link: http://www.searay.com/boat_graphics/electronic_brochure/Company1729/1C1_25_74DEIP4PY0U.pdf

My boat doesn't bog-down at the top end, but it just doesn't have any more RPM/Speed for the last 1/4 of the throttle travel. May be timing advance, plan and simple. I verified that the butterfly is wide open at full throttle.

 

[jadams2009]

Well, after talking to a mechanic I have decided to get the props reworked. He seemed to think that the underperformance at WOT (4100 RPM / 36 mph vs 4600 RPM / 40 mph) was most likely a prop issue rather than timing, sensors, etc. Based on some internet-based prop calculators, my prop slip % seems to be rather high at 23%, whereas BoatRBoy (Mark) figures indicate prop slip of 10.5% (4400 RPM, 22p prop, 41 MPH).

Since I bought the boat used, I am not sure of the trueness of the props. The surveyor did comment that one of the 3 blades on the rear-most prop was slightly off pitch, however there is no vibration and he didn't think that it was a substantial issue. Cost is about $200 per prop. We will see this weekend. In the very least, I will have shiny props and will have eliminated another variable.

Another mechanic thought that I still may have a dead cylinder (injector, etc), however I know what that performs like - since I had a bad plug wire recently. Let's just say that if you loose a cylinder on the 7.4L MPI, you will have a heck of a time getting on a plane in a '99 Sundancer 270 full of water, gas and 3 people.

If the reworked props don't work, I will go back to looking into the timing advance, sensors (TPS, MAP, etc) and injectors. I have 39-41psi on the fuel rail. I am not quite ready to sink $400 into Rinda's Mercruiser Scan Tool to do a DEEPER dive... yet.

 

[boatrboy]

Well, maybe I need a prop change to 22p. I was going to have the props reworked over winter, but...

Mark - do you know if your props were original? SeaRay's prop chart for '99 lists our configuration with 24p and a WOT of 4600.

Link: http://www.searay.com/boat_graphics/electronic_brochure/Company1729/1C1_25_74DEIP4PY0U.pdf

My boat doesn't bog-down at the top end, but it just doesn't have any more RPM/Speed for the last 1/4 of the throttle travel. May be timing advance, plan and simple. I verified that the butterfly is wide open at full throttle.

My props were the original to my knowledge. I have polled and looked at several 270 da and found that the props vary between 22 and 24. I noticed the descrepancy in the Sea Ray link years ago and this has made me question mine over the years. But after seeing alot of 270's with 22s, and mine hitting 41 mph, I decided to stay with the 22s. As for the RPM - I have the Mercuiser manual open and it reads "WOT = 4200 - 4600" with an "accurate tach". I have replace my tach with the digital hourmeter searay tach, but I have not verified the accuracy and 4400 feels safe to me.
FYI - I bought a jumper to time my boat this year, but even though I guessed before getting the tool, there was little performance difference after setting the timing properly. The tool is nothing more than a connecter with the appropriate wires jumped. It cost about 10 bucks at the dealer.

Good luck

 

[jadams2009]

Thanks Mark for the reply. Your prop slip % is very good and mine is way too high - based on our performance numbers.

I called the prop shop that reworked my 24p props to get an update. They said that the two props were both off pitch, especially the rear prop - with one blade considerably out of pitch. There were no nicks per se, however they told me that it had lost 1/2" of circumference and thinning around the outside due to operating in sand. I guess the prior owner didn't worry to much about kicking mud in the shallows. At least he kept his boat very clean.

We will see the results this weekend. Hopefully it was $400 well spent and I will get closer to 40 mph.

I will have my paper clip and timing light ready in case I decide to set the base timing.

 

[jadams2009]

Latest performance after this weeked (with reworked props):

36MPH/37MPH @ 4300 RPM (WOT) - I am now in the published 4200 - 4600 WOT range, however top speed didn't significantly improve.

Slight improvement on the top end. Significant improvement out of the hole. Got up on plan quickly without the need to trimming the tabs down... just needed to change drive angle.

 

[BonBini]

Theresamarie11: I'm a little curious on how or if you made out. I was looking at some numbers on the 260. Looks like a 6200 lb dry weight boat with 310 hp. Your looking for 45mph:huh:. ...Ron