Albin 25 with Universal M25 engine - too slow

[PugetPete]

I am the newest owner (inherited - more or less) of a 1971 Albin 25 with a Universal M25 installed. I have no previous experience with any inboard boat or diesel power.
First cruise achieved only 5.5 kts at 1850 rpm - throttle pushed to the limit. It will rev higher in neutral but not under load.
Any suggestions on where to start to achieve the 7 kts cruise? Unsure if prop is original, bottom is clean.
I tend to think the boat is simply repowered with a wimp engine.

If I were to re-engine, what would be a ball-park figure to get something more skookum, installed (I don't have a trailer and with the cabin design, looks like a challenge to pull old and install new engine). Rebuilt is fine. I know I'm not going to break a plane on this boat but that 1.5 kts adds up.
Don't beat me up too bad, just learning.
Thanks!

[joreyn]

Pete, your hull speed should be around 6.5 knots I would think. You don't need much power to push her along at that speed.

Since the engine revs higher in neutral than under load, I'd check your prop first. It may need tuning, and the prop shop may have some thoughts about the best pitch for it.

Also, how's your bottom looking. If you have a lot of marine growth, that will slow you down a lot.

[N4QC]

Make sure that the engine is operating according to spec. This would entail using a hand held tach in order to verify the RPMs. According to a spec sheet that would be 3000 in neutral and you should be in the range of 2100 to 2600 under load. The hand held tach will also confirm your gauge. Harbor Freight has had them on sale as well as a hand held laser thermometer at times. They are a good addition to your tool box.

The spec sheet can be found at:

http://www.marinedieseldirect.com/unive ... tions.html

Verify that your M25 is covered by that spec sheet...

Have fun,