20hp too small for 25 Albin Deluxe?

[Fredstraw1]

Am repowering my 25 Albin Deluxe. I have a line on a 27hp Isuzu that is in unknown running condition but reported as "good". I have also come across a 20 hp Yanmar that can be seen running and is reportedly rebuilt. Whats the consensus, would that be underpowered?

[LopezMike]

Is the Yanmar a two or three cylinder? The three is noticeably smoother. Same thing with the Isuzu.

I have a 3GMF30 Yanmar which is rated in the mid 20's. Maybe 27? But I cruise at 2000 rpm around five kt's and I doubt that I'm asking 20 hp from it.

For what it's worth, the previous owner kept a good fuel log on his last trip from southern B.C. to Alaska. Cruising at five kts., he averaged 1.09 liters per hour.

Mike

[ssrig]

I am pretty sure there is information on power required to go hull speed on this site and if I remember right it was something like 9hp? Hull speed is in the 5knot range, 5.6 hp maybe?
If you plan any travel in high tidal flow the extra power can help gain some extra speed. Sounds like 25 hp is a popular all around choice.

[DesertAlbin736]

Depends on which hull type, full displacement ("Albin 25 badge, no flare on bottom near stern) or semi-displacement (post 1972 model year, Albin 25 deLuxe badge). Agree with LopezMike, I have same Yanmar 3 cyl 24 HP 3GM30F & love it. But La Dolce Vita is 1971 full displacement, 6.5 knots top end at 2,350 RPM. If you have later deLuxe variant you'll want a bigger engine, 3 or even 4 cyl, +/- 35 HP. I log all fuel & engine hours & over 9 years average 0.4 GPH, which is about 1.4 L/hr.

[SalishAire]

Just food for thought: When we had our 60,0000# 46 ft Nordhavn with a displacement hull the emergency (AKA: "wing") engine was a Yanmar 3 GM 30 rated at 27 HP. With that engine we could do 4.5 - 5 kn (despite requiring the rudder be directed several degrees to stbd to make up for the port location of the propeller). When we purchased A25 Hyacinth we had no concerns about it being underpowered as it had the same Yanmar 3 GM 30.

[Burton]

Great question. We have a forty hp Yanmar in our 25 Deluxe (semi-displacement). We hit 12 kts when the boat was nearly empty and the prop over pitched. Another consideration….

We have some pretty fast tidal currents here in Maine and I’m glad for the horses we’ve got. The previous owner had the prop seriously lugging the engine— injectors carboned up really bad, engine at WOT over a thousand RPMs under rated Yanmar WOT RPM. Did all the calculations for a new prop with the boat empty—- wrong! (WOT is now a hundred under specs, pretty close.) That’s all to say that it would be wise to get info from people with same hull as yours, same engine you plan, to get the right size prop— we’ve spent a pile of dough getting a new prop, then getting it repitched.