Hill Marine Props and Fuel Consumption

Michael T

Late to the discussion but love this topic because, as usual, it brings out the best and brightest ideas on the best forum in the world. Mercruiser has stated in the past that their engines leave the factory with a +/- 5%  HP rating as compared to posted specifications. As some of you may remember my experience with twins was with 2013 twin Mercruiser 350 Mags with B lll drives and 2014 twin 502 Mags with B lll X drives. Both sets of engines were monitored by the Vesselview system and neither showed any significant deviations, engine to engine, in RPM or MPG. That also accounted for any difference in alternators etc. IMO the difference in fuel consumption you mention is abnormal and indicates a problem. Like some of @212rowboat observations. Regarding a misaligned shaft - it would have to be some wobble to account for 300 RPM and a significant fuel burn difference. be interesting to see what accounts for this!

YYZRC

I am going to remove the outdrives for winter (as I have to remove the transom assemblies) and when I reinstall in the spring I will swap the outdrives to see if the problem follows the drive. 

captkevin

Rereading from the start & isn't 135 on the low end for compression.? Shouldn't the numbers be more like 160?

YYZRC

I forgot to open the throttle plate when I did it so that may have impacted the result. 

https://www.perfprotech.com/blog/boat-and-engine-technical-tips/marine-engines/mercruiser-gasoline-engine-compression-test

That article says 100psi minimum. I’m just happy they’re all in the same range. 

captkevin

did a little research & 150 is considered good. 130 is considered low.

LaRea

YYZRC said:

... I also need to come up with a way to determine if the drives are lifting at the same rate when trimming up.  ...

In the water?  From the swim platform, reach down with a boat hook until you are touching the propeller hub.  Have the mate raise the drive, and time how long it takes from bottom to top.  Repeat with other drive.  

YYZRC

I’m not sure that trimming at the dock is the same as trimming at 4000 rpm. Last fall while on the hard I actuated the trim switch briefly (the one that controls both drives) and measured each drive from the skeg to the hull (more accurate). One drive is definitely and not insignificantly slower but that could also be battery related as the engines were not running and I assume the trim runs off the relevant start battery. Again, lots of variables. 

Grahamu

If both drives are all the way down at 4000 rpm and you still have the same fuel burn I think you can discount drive trim being a major part of the problem.

LaRea

OK, so get on plane with drives all the way down.  Raise both drives until the bow starts bouncing, then kill the throttles.  Use the boathook to see if one is higher than the other.  

YYZRC

Grahamu said:

If both drives are all the way down at 4000 rpm and you still have the same fuel burn I think you can discount drive trim being a major part of the problem.

Great point. I wasn’t monitoring burn with trim all the way down. 

212rowboat

If the valves weren't seating as they should due to lose rockers you'd have to do another compression test or leak down to see where you're at now... that first test is out the window.  

captkevin

Will be interesting to see how much adjusting the valves changes the compression.

YYZRC

@212rowboat wouldn’t loose rockers mean the valves are fully seated/not opening fully and an overly tight rocker would mean the valve might be held open slightly?

YYZRC

No change to fuel consumption after the valve adjustment. This is drives fully down no trim tabs. 

Michael T

@YYZRC .....apologize if this has been asked and checked. With your posted numbers all I can think of is that your sender is off. Do you have confirmation that each engine is ONLY drawing from one tank - and - have you checked the levels of each tank by, for example running the boat then topping-off each tank to compare the difference - and - made sure no crossover valve is open? Have you swapped senders? On my 2016 Rinker EC 360 (I believe I posted the saga) a number of expensive parts and a lot of labor (warranty thank God) were replaced before a cheap (want to say $25.00) sender was found to be erratic. I am now officially hooked on this thread!  

YYZRC

@Michael T I actually disabled my crossover (removed handle) and it is closed. As you might remember, the crossover valve handle on the 360 catches on your clothes sometimes when climbing out of the bilge. 

Actual fuel burn is definitely higher on starboard - every time I fill, starboard takes more fuel. That is in small part due to the genny but I know I’m burning more fuel because the throttle is open wider (binnacle lever on starboard further forward) to maintain equal RPMs.

I think at this point it must be a weak cylinder or two on the starboard motor. Starboard maxes out at around 4700 rpm and port will run up to 5000 rpm no problem.

Will do more diagnosing in the spring I guess. 

tricountytrail

I'm chasing the same issue.
see 
https://rinkerboats.vanillacommunities.com/discussion/13746/fuel-injector-question#latest

twin 496 mags bravo 3s

WOT Port 4500rpm Starboard 4900rpm 35.3MPH
Loaded 4 people full tanks and tools
Total fuel 183 gal @ $6.60 = $1205.97 Port 99 Gallons Starboard 84 Gallons
the port engine also lacks power at cruise port needs more throttle. New plugs and wires new filters fresh non ethanol fuel. After Labor Day I'll be checking fuel rail pressure, if they look good I will probably have to do a compression test. if they are off I will pull regulator and injectors on port engine.

Fuel Pump pressures Port 40 psi-start 1 min-34psi 2 min-34psi Starboard 45 psi-start 1 min-37psi 2 min-36psi 38-40psi running

YYZRC

Spent two hours with a great tech going through possibilities. Fuel pressure, timing, vacuum, misfire testing, swapping ECMs, etc with the Merc scan tool. Everything checked out normal. 

YYZRC

captkevin said:

Rereading from the start & isn't 135 on the low end for compression.? Shouldn't the numbers be more like 160?

FWIW, when I mentioned to the tech that I did the compression test and the results were in the 130s his immediate question was did I have the throttle plate fully open. I said no and he said that my real numbers would be +25 to +30 had I had the throttle plate open. Hope this helps someone. 

captkevin

That is good news. You numbers would be where they should be.

Spyderweb

Sounds like good news all around!

oscar1

YYZRC said:

No change to fuel consumption after the valve adjustment. This is drives fully down no trim tabs. 

what model of simrad gps do you have instaled. thx 

YYZRC

Those are GO9s @oscar1 - good to hear from you!

oscar1

Thx, bro.  I am very busy doing my pool renovation at home.

YYZRC

Bringing this thread back to life. I swapped the drives and the excess fuel burn is now on the port side, so the fuel burn difference would appear to be linked to the drive/props.



I can't fathom how the issue could be with the drive itself as if there was some issue with the gears/friction, the drive should have grenaded by now. I've put at least 10 hours on the drive since I first noticed this issue last summer.

Both sets of props are Hill Marine stamped 20p and purchased directly from Hill Marine, but purchased at different times. I'm now wondering if the issue is with the props. When the water warms up, I will swap the props and see if the issue follows.

tricountytrail

tricountytrail said:

I'm chasing the same issue.
see 
https://rinkerboats.vanillacommunities.com/discussion/13746/fuel-injector-question#latest

twin 496 mags bravo 3s

WOT Port 4500rpm Starboard 4900rpm 35.3MPH
Loaded 4 people full tanks and tools
Total fuel 183 gal @ $6.60 = $1205.97 Port 99 Gallons Starboard 84 Gallons
the port engine also lacks power at cruise port needs more throttle. New plugs and wires new filters fresh non ethanol fuel. After Labor Day I'll be checking fuel rail pressure, if they look good I will probably have to do a compression test. if they are off I will pull regulator and injectors on port engine.

Fuel Pump pressures Port 40 psi-start 1 min-34psi 2 min-34psi Starboard 45 psi-start 1 min-37psi 2 min-36psi 38-40psi running

Updating my post as I found MY issue.

here is my issue just checked my drive ratio while servicing my drives port drive 2 turn to one on output (2:1) while the starboard is 2.2 turns to 1 (2.2:1) It has a metal tag that states 2:1Previous owner must have it repaired or changed.
WOT Port 4566rpm Starboard 4895rpm 39MPH
Cruise Port 4194 rpm Starboard 4217 rpm 34 MPH Port engine throttle advanced more apx 300 rpm
Did stall test both engines apx 2000rpm in gear starboard wot easily reached 4500rpm port barely made 3800rpm
I was starting to check port engine for lack of power but this explains the 400 rpm loss at WOT MERCURY BRAVO THREE BOAT PROPELLER 48-823665 24P| (xx" X 24 P)????  INNER  Both Drives Props Checked MERCURY BRAVO THREE BOAT PROPELLER 48-823666 Mercury 24P (xx"x 24P)???   OUTER

captkevin

Hard to believe someone put on a different ratio drive. Not cool

YYZRC

Well, I finally solved this after almost an entire season of troubleshooting and parts-swapping. 

My saga started after (gently) hitting a rock. I installed a brand new pair of Hill 4x4 props and I had the damaged props repaired. Today I removed the “new” 4x4s and installed the repaired ones. Both engines now run at same throttle position and almost identical fuel burn rate. 

Turns out that Hill Marine sent me a propeller that is stamped as 20p (same as my original props) but it is not. I have reached out to Hill Marine and I will post a final update with the outcome. 

tricountytrail

Glad you got it figured it out. Its frustrating until the problem is solved.

johnny44

@YYZRC curious to know how you uncovered that the props weren’t 20p and curious to know Hill Marine’s response. Did you send the props back to them for diagnostic?