3 and 2 blade props for a Cat 30 w/universal 25

[Tim Dranttel]

I've got an 86 Catalina 30 with the Universal 25 21 HP desiel. It was bought with a 3 blade 13 X 13 prop and a spare 12 X 10 two blade. The best RPM I've seen is 2100 wide open resulting in 5.5 knots. I'm down to 1700 RPM and 4.5 knots now but I think (and hope) that the prop is fouled. I'm awaiting warmer water temps to dive on it. 13 X 13 seems like a lot of pitch to me but I do not know if it was repitched. I'm looking for a good compromise between power and speed. Right now I have neither as a good wind or sea pretty much stops me dead in the water. Questions:1-is this or what is the right size 3 blade?2-to save the cost of a new prop would I be better off rehanging the 2 blade?3-is there a way to verify, through measurements, the pitch of a prop?Any help would be appreciated. Thanks in advanceTim

 

[Rick]

Fouled?

A 13x13 prop should be the right size for a M25 engine. Check for fouling by running the engine in neutral to see if you get full RPM (should be over 3000)with no load.If your engine doesn't run any faster with the load off than maybe something is wrong with your motor.If you get full RPMs with the load off then you need to go for a swim. I have found that wearing long underware under a wetsuit makes 52 degree SF bay water tolerable for 20 to 30 minutes - long enough scrub the bottom and prop.

 

[Richard]

Fouled

Its probably fouled with barnacles, I have 13X14 on my 87 with the same setup and can get 2800 rpm without any trouble. I can cruise at 6+ knts at around 2100. You may want to check your tach to be sure. You can send the props out to be measured and repitched if necessary. They can also recommend the correct pitch for your boat and engine. (13X14 was recommended for mine)Good luck!

 

[Kevin l. Woody]

Fouled possible.

Dear Tim,Thanks for the great challenge for me. Yes the propeller could be fouled. If it were fouled in any manner you will experience a great deal of vibration. Is the current 1,700 RPMs achieved because you are tied to a dock? If so this will explain the reduction of RPMs and the mass increase of what appears to be drag to the engine.If not a propeller fouling I would guess that something has created an injector blockage. If the numbers are correct about the past overloading you may simply have created a great deal of carbon and know the engine is in need of an injector clean up. Clogged injectors, whether gas or diesel, will result in a mass reduction of RPMs and engine output. Our Catalina records show that the correct three blade is a 13” x 10”.Our records for the two blade show a 12” x 12” In either case of your existing props could possibly be re-pitch by a local prop shop. ? . Your local prop shop has a tool, which can measure the propellers pitch. If you have any other symptoms which may help me to help you, please pass them to me and I will look them over. If you choose to do this please post it again as a letter and not a response to this note. Thanks Kevin