First Day back on the water... couple of q's

[krisnowicki]

I got the 305 running like a top. But I have lost about 40 hp in my motor switch from the vortec 350. I was running a 14.5 x 21 inch prop. Today when I went out i was using the same prop. When I go to WOT off from idle she revs up to about 2300 then sits there for about 20 secs until it gets on plane. Then it will go up to about 3300 and thats it. When it is not under load it will rev and hold up to 5500 but i never do that. Also since my when it is not under load I can see the tach show the 650 idle to 5500 with no jumping the tach has to be right. Also, I was doing about 30 mph (29.2 gps)at 2300 with a 21p prop. This computes with the prop calc. So my questions are, 1. Is this typical behavior of a boat that is way over proped? 2.if so is the 21 to 19 jump going to be enough or should I go to a 17? I do tubing and cruising. 3. If not what would cause this to happen.?

 

[Haut Medoc]

Re: First Day back on the water... couple of q's

I would go to a 14x17.......
Don't lug your engine with that old prop or it won't last long......​

 

[krisnowicki]

Re: First Day back on the water... couple of q's

I found a 15x 17 in town i think i am going to do that. I am not going totake her back out with the 21p on. Today was tough enough.

 

[Bondo]

Re: First Day back on the water... couple of q's

I found a 15x 17 in town i think i am going to do that.

Ayuh,...... Good Idea......Though it Still might be Too Big.....

 

[krisnowicki]

Re: First Day back on the water... couple of q's

I went out today 15x17. Planes at 2200. IF i open her open from a stop she revs to 3300 then gets on plane then goes to about 4000 after trimming right she is at about 42-4300 do I need to go down to 15? its a comfertable ride this way...

 

[whywhyzed]

Re: First Day back on the water... couple of q's

i......

 

[tmh]

Re: First Day back on the water... couple of q's

Are you using SS props?

Your performance sounds exactly like mine with a 305 that vintage and a fairly heavy 19' deep V. I wound up with the 17" SS prop maxing out around 4200-4300 rpm like you're seeing. Hole shot was fine and just didn't seem much better when i tried a 15" for water sports. The 17" did fine for everything.

Interestingly, i just bought a 350 vortec engine to swap into my boat for the 305 (next week i hope). I'll be looking at a 19" or 21" prop I figure. You and I are going in different directions i guess.....

 

[krisnowicki]

Re: First Day back on the water... couple of q's

So I took 5 people plus gear lets call it about 1400 lbs. When I was out I couldnt get over 3300 rpm's but by my self I am seeing 4200. Should I prop down to a 15. I was getting about 34 mph with my gps. I am thinking of going to a 15 but. I am surprise that I am losing 6 inchs at the prop with the engine switch.

 

[Don S]

Re: First Day back on the water... couple of q's

I think this thread needs to go to the prop forum.
Sounds like you really need more than one prop to me. Depends a lot on what you are doing that day, but even by yourself you are just barely in range, and when loaded, you are really lugging that engine big time.

 

[krisnowicki]

Re: First Day back on the water... couple of q's

am I going to need to go to a 14? I mean that is a little prop for a big boat