Engine RPM creep slowly from 4000-4500

[muskyfins]

When getting up on plane, engine jumps easily to 3000, then climbs up to 3800 in "normal time". ~10-15 secs. Then once on plane, if I keep the throttle down, she take a long time to creep up to 4500. Like 2 minutes-almost across the lake. It is a very strange phenomena that i'm sure I'm not doing justice on an internet forum. I've never had a boat do this. All in all, I don't think there's anything "wrong". What do you think?

2000 Rinker FV270, 5.7 TBI, Bravo3 22P

 

[tpenfield]

I am thinking it is the 5.7 . . . . Once you get up to the 3800 RPM range, there is not much prop slip, so it is a matter of having the horsepower of the engine bring the boat faster and faster, which the 5.7 does not have a lot of extra capacity to do that. I am wondering if you turned a bit during this 2 minute process, if it would further reduce the climb to 4500 rpm.

Has it always done this, or something that changed.

 

[muskyfins]

it's always done this. (first season with this boat) And in the grand scheme, I wouldn't classify it as a problem per se. But my previous (heavier) cruiser with an older 5.7 didn't do this.

But it does seem like a HP issue. This is my first TBI marine engine. So far I'm not impressed vs my old carbed version. FWIW, it takes longer than I wish to plane at all and that's with a B3. It's especially noticeable with extra passengers aboard.

The next one will have either a single BB or twins

 

[alldodge]

Taking its probably the control and stress and/or slack on the cables along with settling in as Ted mentioned.

So far as performance between your 95-265 and 00-270 you just have a tad bit more boat from what I see.

95-265 weight 5775. beam 8'6" length 28'
00-270 weight 6200, beam 9'1" length 28'

Agree twins or BB

 

[Bondo]

Ayuh,..... Drop some pitch on the props,.....

 

[achris]

Ayuh,..... Drop some pitch on the props,.....

If 4500 is max revs, ^^^^^

 

[muskyfins]

IIRC-max revs on this engine is 4400-4800, which makes 4600 that "middle ground" I'd like to avoid changing out props if possible.

It's not scientific, but it "seems like" an engine issue. It is very strange. Spent a lot of time on boats and never seen anything like it. Clogged secondary fuel filter? Plugged jets in TB? Some other weird thing out of left field? I'm sure I'm missing something..:noidea:

 

[Bondo]

IIRC-max revs on this engine is 4400-4800, which makes 4600 that "middle ground" I'd like to avoid changing out props if possible.

Ayuh,.... I'm sure you do,..... but that's ignorin' the Hippo in the room,....

Ya prop for the Top of the rpm range pushin' a heavy barge,....
Mid-range is too low, luggin' the motor all the time,....
Add people, 'n it really lugs the motor,...

'ell,... 5 Grand Wot would be Better than 4600,... Especially in a heavy hull,....

 

[achris]

Ayuh,.... I'm sure you do,..... but that's ignorin' the Hippo in the room,....

Ya prop for the Top of the rpm range pushin' a heavy barge,....
Mid-range is too low, luggin' the motor all the time,....
Add people, 'n it really lugs the motor,...

'ell,... 5 Grand Wot would be Better than 4600,... Especially in a heavy hull,....

Totally concur. My engine will bang on the rev limiter (4950) with the prop I run, but if I run the 'right' prop (gets me dead on 4600) the boat and engine are a proverbial dog. The other thing to consider is the tacho. Are you using a properly calibrated tacho, or are you running off the dash tacho? Dash tachos are notoriously inaccurate. And to quote Ford Prefect, "I wouldn't trust that thing to speak my weight"....

Chris.......

 

[HT32BSX115]

When getting up on plane, engine jumps easily to 3000, then climbs up to 3800 in "normal time". ~10-15 secs. Then once on plane, if I keep the throttle down, she take a long time to creep up to 4500. Like 2 minutes-almost across the lake.

2000 Rinker FV270, 5.7 TBI, Bravo3 22P

Howdy,

That FV270 is a fairly big heavy boat. I'll agree with everyone else and say that since you are already rather underpowered, if the engine is running properly, you'll get a better top end by propping the boat so that the engine turns right at the top of the WOT range when you're loaded where you'll normally run it.
(full fuel, 4 people and gear etc.... AND I assume that you have cleaned the hull of growth, it's NOT painted with a rough coat of anti-foul paint, and it's not overloaded/waterlogged)

While this is all happening, what are you doing with the drive trim and tabs(if installed)?? What is your drive ratio and have you tried a different TACH yet?

With my Bravo III, I start out with the drive trim DOWN/IN and slowly adjust (OUT) in small bursts for maximum speed as it accelerates. (TABS full-UP)

And then once at max speed, make small adjustments IN or OUT to fine-tune.

Did you modify(raise) or remove your swim-step or does it drag in the water during hole-shot?

 

[muskyfins]

I want to thank you all for your help...this thread reads like a who's who of some of the folks whose opinions I really admire on this forum. Pat yourselves all on the back!! :clap2: :clap2: :clap2:

​To address some of your suggestions/questions-

• This has always happened-wasn't something that appeared out of the blue. (first year with this vessel)
• Bottom IS painted, but smoother than most I've seen. Not the really rough stuff. But not the hard racing style either.
• Marine growth is lowest I've had in this body of water ever. +/- 20 years here. Due to above mentioned paint. (Ablative)
• She's running hard at 4600. I'd be a little nervous to run up to 5000. But I'd be willing to give her a try. (time and funds allowing)
• Right now using dash tach. Could be off a little I suppose. Has been a really tough summer time-wise this year and haven't been able to do the normal tinkering as I like. I will say, I know the creep really happens because I can hear it. So the creep itself isn't a tach issue. I just cant prove if it's between 4000-4600 or 4200-4800. Yes important to get test tach.
• It may be water logged, but it happened the first day i put it in the water, so now she'd just heavier. All in all, I see no other evidence of waterlogging. I have the same top end and other handling characteristics as day 1. I have not checked by drilling holes.
• Didn't log drive ratio before spring splash. or I lost the info before logging. Same applies to serial number of drive. But I'll look again.
• I start drive down/in, once it breaks, i trim up to desired attitude, and throttle down to 3900-4100. No tabs usually, but i have started experimenting. The use of tabs has no effect on this creep issue. It planes and hits about 4000 one way or the other, and then goes into slow motion for the next 400 rpms
• Factory swim platform. Finished on underside I believe. Kinda short in my opinion all in all. Might be dragging, but I don't think so.

The general consensus here is prop. I will focus my attention there. But I'll admit, it won't be until spring test and tune. And depends partially on life schedule at that time. Also, as I stated it's more of an annoyance than a "problem" except that lugging the engine is no good.

If I just didn't have this damned job interfering , I'd have plenty of time for boating.:laugh: :lol: :happy:

 

[HT32BSX115]

[*]She's running hard at 4600. I'd be a little nervous to run up to 5000. But I'd be willing to give her a try. (time and funds allowing)
[*]Right now using dash tach. Could be off a little I suppose. Has been a really tough summer time-wise this year and haven't been able to do the normal tinkering as I like.


I will say, I know the creep really happens because I can hear it. So the creep itself isn't a tach issue. I just cant prove if it's between 4000-4600 or 4200-4800. Yes important to get test tach.

I'm with Chris, TACHS are frequently off especially at higher RPM..............I'd get another TACH and test to be sure.

[*]It may be water logged, but it happened the first day i put it in the water, so now she'd just heavier. All in all, I see no other evidence of waterlogging. I have the same top end and other handling characteristics as day 1. I have not checked by drilling holes.

Don't drill holes. You have a trailer? go drive your vehicle+ trailer over a scale and get a good unloaded weight. Then trailer the boat to the same scale and get a good weight with NO gear and either an empty or full fuel tank.

[*]Didn't log drive ratio before spring splash. or I lost the info before logging. Same applies to serial number of drive. But I'll look again.

It should be either a 2.20:1 or 2.00:1 drive and should be marked with a sticker.......It's pretty important to know your ratio, RPM and actual speed(GPS) to make any sort of decision regarding props.

If the ratio isn't marked, with the boat on the trailer, remove the spark plugs and slowly turn the engine with the drive in gear and turn the engine 2 revolutions(exactly)........Have a helper observe the prop make either exactly 1 revolution (2.00:1) or slightly less than 1 prop turn, (2.20:1) or slightly more (1.81:1....very unlikley you have a 1.81:1)

[*]I start drive down/in, once it breaks, i trim up to desired attitude, and throttle down to 3900-4100. No tabs usually, but i have started experimenting. The use of tabs has no effect on this creep issue. It planes and hits about 4000 one way or the other, and then goes into slow motion for the next 400 rpms

TABS won't do a lot for your holeshot. up or down until you get moving. At high speed, they increase the parasitic drag and reduce top speed........

[*]Factory swim platform. Finished on underside I believe. Kinda short in my opinion all in all. Might be dragging, but I don't think so.

I did a little reading, there's a problem with some 2000's FV270's. Seems they put that swimstep too low....... Evidently Rinker did come out with a "fix" but they didn't pay for it. I guess owners had to foot the bill on some of them.

The general consensus here is prop. I will focus my attention there. But I'll admit, it won't be until spring test and tune. And depends partially on life schedule at that time. Also, as I stated it's more of an annoyance than a "problem" except that lugging the engine is no good.

Since you're using 22p props, you don't have a LOT of wiggle room. You can go to 20's but that's about it unless you have a 2.00:1 drive. You could go to 2.20:1 and it would help a little.

If I just didn't have this damned job interfering , I'd have plenty of time for boating.:laugh: :lol: :happy:

I think we ALL wish that!!! I think I am going to retire though

Cheers,


Rick