Is this what I should be expecting?

I have a '95 Cobalt 220 with a VP 5.8FL motor (235hp) and DuoProp drive (regular, straight up, white DP model). I recently put on new B6 aluminum props because the old ones were badly torn up by the previous owner. The old ones were also B6s and probably original equipment.

At WOT, I'm seeing just a hair over 4000rpm and a GPS speed just a hair under 40mph. The WOT range for this rig should be 4000-4400rpm so I'm in the zone, but it just seems that I should be getting a bit more speed out of her. Does this jive with your experiences or am I missing some power in the engine?

Re: Is this what I should be expecting?

This wasn't really a prop question as I had B6s before and have B6s now, but it got moved here. Really, I'm looking for some info on whether these numbers look good for this combo or if I should be searching for anything that might be robbing me of power in the motor (plugs, carb adjustments, etc.)

Re: Is this what I should be expecting?

Your engine might be missing some power that can be recovered with a tuneup. You may also just need to drop down to a B5 set. Having "typed" that, it is an expensive experiment with prop swaps on the DP drives

I have a 22 foot Cuddy cabin with a VP 570DP which is a GM 5.7l with 4bbl carb and DuoProp DP-A drive. Your boat is probably heavier but mine is not a lightweight. I run B5's and can get 46+mph at about 4500rpm. I can get 50+ with B7's but I usually am towing with several people in the boat and the B7's are for higher top end and cruising speeds so I run the B5's. With B5's I can hit 45mph with almost any kind of load and cruise at 40 all day at 3800-4000rpm. I just watch the RPM when not loaded.

My engine is rated at 275HP "in the Brochure", but that is at the engine and not the propshaft. I would guess mine is 230-240 HP at the prop shaft. I am not sure what the 235hp rating means on your 5.8l, I.E. at the engine or at the propshaft, the industry changed how they rated them sometime after my model year of 1991.

Re: Is this what I should be expecting?

You should do a compression check first if it has not had one recently just to be sure of the general health. All the rest is electrical and fuel maintenance. Also is a good idea to weigh the boat to make sure it is not lugging around any extra baggage.

Re: Is this what I should be expecting?

A compression check is a good idea. I'll add that to the "to do" list. A weigh-in will have to wait until the end of the season as she is in the water for the summer. The good news is that the bilge has remained bone dry except for one day just after a storm where I pumped out barely a gallon's worth.

Re: Is this what I should be expecting?

Got any pics? I boat "vicariously" to save costs...

Re: Is this what I should be expecting?

Maclin said:

Got any pics? I boat "vicariously" to save costs...

Click to expand...

So far, just this one that my dad took while on the way to Pappa's on the Lake for Father's Day.