1989 Classic fifty 45hp

[Randall89tx17]

Hey guys I just join the forum.
I have a 1989 Tracker tx17 with a classic fifty 45hp. I am running a 11 pitch prop and getting 26 mph at 5500 rpm. When I take off the engine runs to 5000 and will stay there for 200 feet roughly, then you feel a bump to the boat as it grabs good water and takes off. My question is, am I under propped and what should I be running? It had a 14 pitch, but it was in bad shape. No cup, bent and chipped or chunks out.

 

[dkonrai]

Re: 1989 Classic fifty 45hp

i had a 14 foot bayliner, ran a 17 pitch prop. it ran almost 40. i had to install a fin to plane faster as it would not get up to plane with the 17 pitch prop. my guess is try a 15 pitch. sounds like your running not enough pitch. my guess is your boat should be getting at least in the mid 30's.
dino

 

[Randall89tx17]

Re: 1989 Classic fifty 45hp

i had a 14 foot bayliner, ran a 17 pitch prop. it ran almost 40. i had to install a fin to plane faster as it would not get up to plane with the 17 pitch prop. my guess is try a 15 pitch. sounds like your running not enough pitch. my guess is your boat should be getting at least in the mid 30's.
dino

I was thinking the same, but wanted to confirm. It's not too easy to find a place locally who has some props to try for this motor. Reason being I got this 11 pitch to get away from the unbalanced old prop. 30's would be great. I'm not looking to fly, but that'd be perfect for running. Thank you.

 

[Texasmark]

Re: 1989 Classic fifty 45hp

Your prop is perfect for that boat. Engine is rated 5500 rpm max at WOT and you are right on. Don't mess with it.

You are apparently ventilating in your hole shot. Ventilation is sucking air into the propwash reducing the load on the prop due to reduced density of the medium and as a result allowing your engine to increase it's rpms.

Several things to consider:

Is your prop ported...(ports are 1 hole per blade just under and slightly to the rear of the leading edge of the blade, purpose of which is to do exactly what you are experiencing)? By getting your rpms up fast you get your thrust up fast and get a faster hole shot.

Other option is turbulence from the boat producing bubbles which get into the prop wash. An aluminum boat with an alum strip running the full length of the bottom (covers where the halves of the hull are welded together) is just such a device....I have one of those on my boat and it does get in the way some times.

Another is engine trim. If you are trimmed (tilted) out too far this can happen too. I deliberately trim out too far so that my prop will break loose as you describe. It gets me a much faster hole shot.

Another is engine position with respect to the bottom of the boat. If too high on the transom it can aggravate ventilation, especially with the "keel" of an alum boat helping.

Changing props with different characteristics can cause different results and you may be experiencing that. If you are getting a good, fast, hole shot the way your are currently, I wouldn't change a thing. To me a good, fast, hole shot is less than 5 seconds from punch to bow down.

Putting a Whale's Tail or such on the engine can reduce the problem if it is sucking air from directly above the prop, but personally, I wouldn't have one on my boat. Buttttt my boat is not like everybody else's boat and some folks use them and like them.

Again, your current prop meets the requirements for propping: Top end of operating range at WOT. That's where they are rated!

Mark