Low Top Speed - 2017 C30

Status
Not open for further replies.
S

skipper207

Member
Joined
Oct 13, 2021
Messages
21
Fluid Motion Model
R-23 (Outboard)
Hull Identification Number
fmlc3029a717
Vessel Name
Islander
Hi,

So, the boat feels great. Nothing seems wrong, RPMs seem normal, engine sounds normal, no problems shifting, transmission oil feels and looks good, no alarms, but the boat will not top 17 knots. I'm maxing out at about 3300 RPM which I think is normal. Earlier this season I was humming along at 25 knots wide open, now I can't get close to 20. I am baffled. I dove below the hull, no excessive growth, nothing around the prop.

Any idea what on earth could be going on? Ever seen anything like this?

Engine has 750 hours, use it regularly and have never felt anything strange, not exactly sure when the issue started as I don't usually speed along much above trolling speed.

I have not tried pressing that low speed button on the throttle, I assumed that would have a more dramatic and have never used it. Maybe I pushed it accidentally?


Thanks ahead of time for any help!!
 
The D6 435 engine is supposed to be WOT at 3600 RPM. I can achieve this in mine even with the boat fully provisioned with water, fuel, and goods, and 3 people and 3 dogs. If the tides and currents are not against me, I typically cruise at 3000-3200 RPM (normal cruise to i have places to be cruise). Within that RPM range, i'm normally cruising at 16-20kn. WOT with a fully loaded boat and I can see 25kn on a good day, but more likely 23kn. You would know if the low speed was engaged by the green LED on the binnacle. Sounds like not if you are at 17kn. How are your trim tabs? are you deploying them fully then backing off to bring the bow down just enough to see the waves strike at the aft end of the bow rails? How full is your fuel/water/holding tank? If you are not able to hit WOT RPM, that is more concerning to me and you may want to seek the advice of a mechanic, or maybe Brian Brown will chime in here.
 
I think my RPMs may be low. I'll have to look again but I think I was capping out at 3300. Nothing to do with how I'm driving it. Not related to trim tabs or growth.

After reading some it could be that low speed mode button which I will check by Friday when I am at the boat again.

I'm writing just to get some ideas. There is the engine, fuel, air, transmission, shaft and prop......problem has to be somewhere in there. Didn't know if anyone would have some ideas I could investigate myself.

Praying I am in low speed mode and that's the issue. I've never used it but maybe someone pressed it by accident.
 
Sorry to say I’m sure it’s not your low speed option. The low speed button is for trolling or marina maneuverability. The low speed slips the the clutch to allow for reduced speed usually below 3.5 mph. When the throttle lever is pushed beyond the preset angle the clutch fully locks up just like if you weren’t in low speed.

How are the fuel filters and air filter?
 
Mike&Sarah -

Thanks for the reply. Well bummer on the switch, but that's what I had initially gathered or I would have tried it already.
I replaced the air filter yesterday (didn't seem too plugged) and will replace my fuel filters shortly. Last changed my fuel filters the end of last season.
 
Has the fine screen at the bottom of the fuel pick-up tube been punched out?
 
After reading couple of your comments here a my thoughts.
" I dove below the hull, no excessive growth, nothing around the prop."
Any growth will slow you down and load the engine. A clean bottom no growth will give you that Max performance. As the summer goes on a thin layer of slime will build up. A few barnacles, and some light build up on the prop and the speed reduces and the engine load increases, rpm drops. This is a good reason to weekly throw the throttle down just to see how things are doing. A fast run weekly will help knock some of the light growth off before it starts to build up.


"Engine has 750 hours, use it regularly and have never felt anything strange, not exactly sure when the issue started as I don't usually speed along much above trolling speed."

The D6 is a common rail engine which fuel/air is electrically controlled so it is less prone to have exhaust gases coke up the turbine wheel of the turbo. It can coke up if the major running operation is just above idle (trolling speed). If the turbo gets some build up on it. The turbo boost may drop and performance may be effected. You have a boost read out from the EVC see what boost number you are getting and compare it to past WOT Boost numbers. If you find a discrepancy then remove the exhaust elbow and inspect the turbine wheel for build up. If you don't have past records of the boost number post what your results are on TugNuts and compare to what others are getting.

Fuel filters restriction can cause loss of fuel and the engine will have loss of power. Normally a well maintained engine that is operated frequently with fresh fuel added will easily make a year without filter changes. A boat that is used but little fuel burned and fuel that sits in a tank for a while requires a stabilizing additive to prevent sludge and water accumulation in the tank. this will shorten the longevity of the filter and require more frequent filter changes. You will find out if this is the case when you change your primary filter and drain the filter housing inspecting for water and debris.
 
Brian -

Filter change showed a pretty plugged up racor; as for the fuel in the filter/housing not much as far as particulates and no water. I added an additive to help clean out the injectors just in case they are gunked up at all.

My boost pressure was 29psi @ WOT. That seems normal, so no need to check the turbo in that case?

Max speed of 20 knots, which did seem a bit better, but still seems pretty low compared to my previous top speed of 26knots.

Everything is running smoothly except for that low top speed. Anything else you can think to check?

Could the prop be slipping? Transmission fluid is topped off and nothing clunky or anything with the ride.

I'm at a loss......
 
Rich -

No it has not. Is this something that you have done or check? Where would I access the screen?
 
skipper207":1l5qpj8f said:
Brian -

Filter change showed a pretty plugged up racor; as for the fuel in the filter/housing not much as far as particulates and no water. I added an additive to help clean out the injectors just in case they are gunked up at all.

My boost pressure was 29psi @ WOT. That seems normal, so no need to check the turbo in that case?

Max speed of 20 knots, which did seem a bit better, but still seems pretty low compared to my previous top speed of 26knots.

Everything is running smoothly except for that low top speed. Anything else you can think to check?

Could the prop be slipping? Transmission fluid is topped off and nothing clunky or anything with the ride.

I'm at a loss......
Click to expand...

Did you change the secondary onboard fuel filter as well?
 
Yes I did. And I do think I've gained a knot or 2 after the change, but she's still moving slow for sure.
 
My previous boat was a diesel Sea Sport With the same symptoms you are experiencing. Fuel restriction suspected. Starting at the engine and working backwards I eventually got to the fuel pick-up tube. When I pulled that out, there it was, a gob of clear gel and fine debris. Not enough to stall the engine, just enough to make it clear somethings wrong here. When I asked the dealer "What's this, I'd rather this crap get sucked up and make it to the two stage filter system, Isn't that what they are there for." He explained, when these tanks are sent out from the factory with tubes installed, the manufacturer does not know if they will end up in a gas boat or diesel. The fine mesh screen is for a gas boat, for diesel it should be removed. Just punch it out.

I don"t know what Ranger does and I haven't checked my own boat yet. I'm going to now, it's due for service anyway.
 
The discussion of the pick up tube in the bottom of the fuel tank has caught my interest. I think I’d like to inspect that as part of my regular maintenance. When reassembling the pick up to do the fuel tank, is there a sealant that should be applied or just reuse the gasket?
Thanks,
Bobby
 
Thank you Rich. I will certainly give it a look!
 
actually, only the sending unit has a gasket. The pickup tube is threaded in. After removing the hose clamps, I've been working on getting the line broken free but it is really fused on. Any suggestions?
Bobby
 
Bobby,
Before frustration progresses to anger, I suppose you could just cut it off and replace the whole line. Please post what you find at the bottom of the pick-up tube.
 
skipper207":33lh0a9h said:
Brian -

Filter change showed a pretty plugged up racor; as for the fuel in the filter/housing not much as far as particulates and no water. I added an additive to help clean out the injectors just in case they are gunked up at all.

My boost pressure was 29psi @ WOT. That seems normal, so no need to check the turbo in that case?

Max speed of 20 knots, which did seem a bit better, but still seems pretty low compared to my previous top speed of 26knots.

Everything is running smoothly except for that low top speed. Anything else you can think to check?

Could the prop be slipping? Transmission fluid is topped off and nothing clunky or anything with the ride.

I'm at a loss......
Click to expand...

I don't think prop slipping is an issue. If that was the case, the speed would be down and the rpm would be up.

The turbo does not seem to be an issue.


The fuel filter primary being dirty may have been some of your issue. If you do a lot of slow cruising and your fuel sits in your tank for long periods of time in damp marine environments it is a good idea to keep the fuel treated. If the primary was plugged up it may be a good idea to replace the secondary. The primary is a 10 micron filter which will let very small particles by and this may foul the secondary. This is not normally the case, but not seeing how fouled the primary filter was it would not be a bad idea to do the secondary now just for troubleshooting.

The 3400 rpm is very close to being ok. The thought process that the engine manufactures use when giving recommended rpm operating speed is. Clean bottom, full fuel, full water, boat equipped with normal load and gear. The engine should turn 3500 rpm + 150 rpm. This gives the variance of 250 rpm loss do to extra passengers and extra gear added and the inevitable dirty bottom. Most boats will perform the best when freshly launched. A CLEAN painted bottom keeps the boat and engine performance where it should be. As I stated in my last post ANY slime will be a drag and lower the engine and boat performance. Having worked on the East coast for a few years I know a boat that sits in the water for a season will have some growth on the bottom. I worked at a marina that was primarily sail boats and many had their bottoms cleaned every two weeks because they would loose performance when sailing. A thin layer of slime would slow them down.

Based on the fact that you have a filter that was somewhat plugged I would (Just Guess) your issue is from a lot of slow cruising and fuel that has been in the tank for a while and a dirty bottom.

There is a screen on the fuel pick up at the bottom of the tank. Diesels do not require a screen. The screen is for gas powered boats that have a anti syphon valve. The screen protects the valve. The screen over time can get fouled when it is used in diesel fuel if the fuel starts to get water and sludge. This normally happens in boats that don't get used often and have untreated fuel in the tank. If you find that your tank has some sludge and debris in it. The best solution is to inspect and clean the tank. Removing the fuel sender is a way to inspect the tank. Your boat is not that old so I wouldn't suspect a 2017 with 750 hours would have a lot of sludge in the tank. That is over 100 hours a season. If all of those hours have been at low speed and the fuel in the tank last all season untreated that could then be an issue. You would be the judge of that!


Before you get too involved. I would change the secondary filter. Then I would throw a wet suit on and give the bottom a scrub. I would suspect you see an increase in speed. Just My opinion!
 
Bobby,

I am very interested in how the process goes for you and if indeed you do find a screen in the intake hose. Would love to get an update after you are able to break the line free.

Phil
 
Don't go crazy yet. Brian mentioned cleaning the bottom. You would be surprised at how just a little growth will degrade speed and RPM.
 
Status
Not open for further replies.

  • Tugnuts.com is the community hub for Ranger Tug, Cutwater, and Solara owners. Since its inception in 2008, the Tugnuts forum has grown into an active and thriving community of more than 9,000 members. It serves as both a meeting place for the best boating community online, and an invaluable archive of information.

  • User menu
Back
Top