Original engine

[tugDreamer2020]

Hello there,
I am trying to figure out what was the type of the original engine for the 2008 Ranger Tug 25 we recently purchase.
The previous owners re-powered the boat in 2018 with a Cummins QSD-2.0L. Also, I am not sure about the original prop.
Current engine is supposed to produce 4000 rpm if propped properly but achieved only3200 rpm as a max load rpm.
Is the current prop too big for current engine?
The current prop: 3 Blade Bronze, Diameter 17 Inches by Pitch 14 Inches.
Thanks,
Dan

 

[knotflying]

RPM can also be affected by how much weight you have on the boat and clean bottom. Make sure those are okay before changing anything.

 

[BB marine]

Send an email to Ranger Tug with the boat HIN (hull identification Number) They may still have records of the build. Assuming a survey was done at time of purchase what was the recorded WOT RPM. When the survey was performed was the bottom inspected? If so was it clean? Based on the prop chart that is the right prop. The question is what engine was installed in your Tug. What is the serial number group and HP ? When the engine swap was done was it a bobtail (engine only) or a engine and reverse gear together? If it was a complete package what is the gear ratio of the Reverse gear? When the survey was done was the engine fully inspected? Fuel system, Turbo, Air filter clean, oil samples taken? Just because an engine doesn't turn full rated rpm does not mean it has the wrong prop. The fact that the engine only turns 3200rpm at max load indicates a potential serious issue. Maybe not right now but if operated this way for a time it will present a serious issue.
Things to check
clean bottom
clean fuel filters and fuel tank pickup
Turbo boost at max throttle, turbo boost at different rpms (record)
Gear ratio of reverse gear
Serial number of engine and HP ( compare this to the original engine installed by Ranger)
Weight of boat ( is the boat wet ) This should have been checked during the survey during moisture checks. If not how heavy is the boat compared to factory specs?

The engine is a 4000 rpm rated engine and should turn +/- 100 rpm, 4000 rpm based on manufactures specifications. If you have a 17x14 prop , clean bottom and average equipment on board and it only turns 3200 rpm. I would suspect it is not the wrong prop based on the specs posted below If the engine swap was in like kind. If you were turning 3700 rpm yes a prop adjustment could be the issue.

download/file.php?id=12
viewtopic.php?f=2&t=15158#p100155

 

[daveo]

Our 2008 / Cummins 2.0 has a prop 17 x 15. Loaded normally, it ran 99% /3750 WOT. I had the prop adjusted, it now runs 97% / 4070 WOT