C-Dory 25 performance issues? Prop? Other

C

Creechers5

New member
I purchased my 2004 25 2 years ago. Powered by 2005 Honda BF-135

Originally we would hit 30 mph at WOT (Didn’t know to check rpm’s at the time) 25 mph with heavy load (family of 7)

After a few months of operation I hit an underwater jetty and destroyed the lower unit and prop. Wrote down prop size but for the life of me can’t find the original prop size. Don’t judge! I’ve learned a lot the hard way last 2 years!

Found a used lower unit and prop online.
Power tech OFS 13” pitch (same as recommended by Ken at Prop Gods.

Since changing the lower unit Performance has been significantly diminished.
At first I could get 25 mph at 5700
Now I am at 19 mph at 5700 WOT!

Just had t complete transom rebuild, engine completely serviced! Fuel system also serviced.

Ken at Prop Gods says prop if correct size must be slipping (not enough cupping)

Murphy’s prop repair says over the phone he seriously doubts it’s the prop.

Maybe it’s the hub in the prop?

Could the hub be stripped on the lower unit?

Open to any suggestions!
Thanks!

Larkin
 
Hub could be stripped, gearing in the lower could be different, prop size/pitch could be different, lower unit could be sitting too low.

Is the lower unit the same part as the one you took off?
Why was the replacement lower unit available (i.e. what happened to the rest of the engine)?

My BF90D has a prop of 13.5x15, so maybe your prop is wrong.
 
The 25 needs a 15" pitch prop at sea level. I have a lot of respect for Ken at Prop Gods, but he does not know or understand the C Dory's. You are better off asking here. (I did talk to him about the issues I had with my 2003 25 with the130 engine.)

A SS prop will do better. But you are way low. Generally when prop hubs are spun, you cannot go at more than an idle. But I certainly would not discount it as a factor.

Is the boat kept in the water? We always think of two issues. One is bottom growth and the other is weight i the hull. So if the boat is light--is there a possibility of water having been picked up and not removed. It is possible to trap a fair amount of water around the fuel tank are under the cockpit. I don't know if your boat has the "steps" in the forward part of the cockpit. You can remove these and check for water around the sides.

Definitely get another prop. I was never happy with a 13" pitch even at Lake Powell (3700 feet). I had to go to an 11" prop there to get up to most effective speeds.

There are also a lot of other issues with props, including rake, and cup which will definitely effect boat speed.

ssobol had given you several other thoughts which are good: 'the motor is mounted too far down, is a definite possibility. Also was the "replacement" lower unit a new Honda, or a SEI new unit. (SEI makes many lower units and out drives. My personal opinion, is that they are not as good as the factory units. A factory unit should have the only gear ratio available for that motor. Unfortunately a SEI could have a different gear ratio-and thus his theory be correct.

Keep us all in the loop!
 
Sounds like hub is ok or it probably wouldn’t get to 17 mph.

Lower unit came off off another Honda with blown head according to online shop but again I seem to have made several questionable decisions so far so could be aftermarket SEI I guess.

As for water in hull, fiberglass shop did a thorough wash down in cabin so there could be water left under cockpit but that should have drained at ramp launching I would think? Bottom of boat is clean as she says on trailer.

Thinking 15” pitch stainless prop must be the answer. Assuming 3 blade power tech or solas? Trying to find prop now locally b4 ordering online.

Thanks for all the help!
 
Most likely the lower unit is the Honda. However my son had a problem with lower unit on a 150, and his was replaced with SEI. I believe. I might check the fluid and magnet on the drain plug, just to be sure that the lower unit is not imploding,

You can pick up the Honda aluminum prop and see how that works. I always carry an extra (or 2) props. (15 x 15 Solas)

A wash down should not leave water trapped, but if water is outboard of the "Box" the fuel tank is in, it could be trapped there....Weight of the boat would tell use a lot, if the prop does not solve the issue.
 
I have to correct my post above. My son used a "rebuilt lower unit"--also ff an engine which went to parts. It had problems almost immediately and he ended up buying what was billed as a new Honda lower unit. (not the SEI)
 
Back
Top