ENGINE OVERLOAD

[Pauld]

2007 Albin 35 CB with Cummins QSB5.9...mechanic says engine is at 100% load when at WOT. Have 4-blade prop. Can't get more than 2990 RPM at WOT...mechanic says should get 3025+ RPM.

My question is what was the factory standard prop? 3 or 4 blade? Anybody have an idea what size/pitch would be the correct prop for this boat? I'm wondering if the current prop is over sized or over pitched.

Thanks for your help.

[Ben423]

2990 is pretty close to 3025. I wouldn't worry about 35 RPMs. Before getting into prop details, you might check how much stuff you're carrying in the boat. It's amazing how stuff accumulates in lockers, shelves, etc. Extra weight affects performance.

[Rondo]

We have the same year 35CB, and the same engine. At WOT we are at 3050 RPM with full fuel and water. We have a 4 blade prop driven thru a 2:1 ZF gear. We are at nearly the optimum, so far as I can determine. With the data you mention, you have nothing to worry about so far as overloading. The small difference could easily be weight, as mentioned by Ben, a less than clean bottom, or prop. current, wind - in short - don't worry about it. The cynic in me thinks the mechanic might be upselling his services, sorry.
3 days ago, I brought her home from the yard after a bottom job. At 2450 rpm, we cruise at 18.5 mph, or about 16 knots. That is about 80% of WOT. At this speed on our boat, things are all singing harmony on the same page. 3/4 fuel and water. At this speed we burn a pinch over 8 gph, good for a boat.
Rondo

[Rondo]

I should have mentioned that you have nothing to worry about, UNLESS, you intend to cruise the boat at WOT. The 80% of WOT figure is widely recommended at a cruising speed.
Remember, diesels are happier when they are working.
Rondo

[Maogwaicat]

I am new at this Albin stuff, 2005 35CB, Yanmar 440 with 840 hours on the clock. (Used to Be Jerry Crews' 'Seacheck'). I started my journey from Chesapeake cruising at about 2700 rpm and getting about 14 knots. Oil pressure above 75, Water temp about 182 degrees. I needed to get to Oriental while marina was open so I bumped up to 3200 rpm, boat went onto plane really nice and we were going about 18 knots. Temps and pressures unchanged. A couple days later I was offshore from Charleston on very smooth sea and I ran just under WOT which appears to be 3300 rpm. I was at 3200, got the 18 knots and same pressures/temps. Ran for about eight hours. Only thing different was adding about a quart of oil. There were no leaks or smoke/steam in exhaust. Am I being hard on the boat or is it just that strong? Previous experience with Perkins and Cummins diesels were that I would get overheat alarm after ten minutes of WOT.