85HP - 1977 Proper PROP for getting out of the "hole"

[John Drew]

I have a 1977 85HP which has a 13 1/4 x 19 prop. I bought it about 6 mo ago so know little about the performance.

I took out the grandkids to pull on a tube behind the boat and it is very slow getting out of the "hole". Runs like a "scalded dog" after it gets up on top.


Now they are wanting to ski, but I don't know if it will get them up. Does the pitch on the pro appear to be correct or can you give me some suggestions on how to get more power at the start? It's on a 1992 Tidecraft Spitfire.

 

[steelespike]

Re: 85HP - 1977 Proper PROP for getting out of the "hole"

We need a lot more info.Please read the stickys at trhe top of the page and get us as much info as possible. It is very important that the motor be able to operate within its rated wot rpm range.

 

[Dhadley]

Re: 85HP - 1977 Proper PROP for getting out of the "hole"

It's not unusual to have 2 props especially with the older motors. The prop to be used for skiing (and as a spare) we won't worry about top rpm because we're more concerned about pulling power for the water toys and it's doubtful if it ever gets run wide open anyway. For the moment we'll assume the 19 is the correct pitch without towing anything.

If the 19 is correct without towing then a 17 will be easier on the motor and the skiier. A 15 will be easier yet. A 15" 4 blade should be even better.

Very general scenarios but the theory is the same.

 

[Bob_VT]

Re: 85HP - 1977 Proper PROP for getting out of the "hole"

Just my experience........ the 85 V-4 is usually happy with a 17 pitch prop and reaches "normally" 5500 rpms........ the 19 is also good but I doubt you are reaching 5500

My best suggestion is to live with what you have Save you a few bucks and the performance difference will be only slight.

Dhadley (I consider him the Guru ) makes a valid suggestion of the 4 blade and I bet you will actually be able to pull doubles with that prop...... The boat will leap out of the hole

 

[Texasmark]

Re: 85HP - 1977 Proper PROP for getting out of the "hole"

I Certainly don't want to "quibble" with what the "old salts" have to say on here.....some having answered your question, by the fact that my experience with the problem you mentioned was solved with a ported SS propeller. The ports are small holes drilled in the barrel of the prop (Vendor supplied item....ported prop) which forces exhaust gasses across the blades of the prop during hard acceleration...like the hole shot, getting skiers up from a deep water start, or a heavy boat up fast.....usually only in SS props but there is at least one vendor that does it to aluminum props which also have cupped blades......both performance enhancers....and an iboats prop supplier.

By allowing the prop to compress air, rather than be limited to turning in the non-compressible medium (water) the engine can rev up faster, thus developing it's HP faster and the end result is a great hole shot with a prop that will give you the top end that you want (that you are currently satisfied with on your current prop) once you are up and running as you mentioned.

Try it, I know you will like it. BTDT and I just drilled out my current SS prop for my current boat because of the same problem and was dissatisfied with the performance of my current HP SS prop............butttt drilling holes into SS props requires some mechanical prowess and the right tools/drill bits......more butttt a reputable prop shop can put the holes in there for you......I happen to be about 75 miles from the nearest prop shop and I have the drill bits/machinery to do it myself, so it is a moot point.

Good Luck,

Mark

 

[John Drew]

Re: 85HP - 1977 Proper PROP for getting out of the "hole"

I found a 13 3/8 x 17 used prop on Craigslist and it is working great. It pulled them out of the water and plained out with ease. Thanks for the advise. The other thoughts are very interesting. Cheers

 

[Texasmark]

Re: 85HP - 1977 Proper PROP for getting out of the "hole"

It's not unusual to have 2 props especially with the older motors. The prop to be used for skiing (and as a spare) we won't worry about top rpm because we're more concerned about pulling power for the water toys and it's doubtful if it ever gets run wide open anyway.

Very general scenarios but the theory is the same.

Do remember that very thing sir. I had a Wizard/Merc 2 blade I called my "Speed Prop" (came with the engine) and a 3 blade in brass/bronze I called a "Power Prop", both to fit a 25 hp 4 cyl Wizard (Mark 30 spin off) running on a 14' wooden boat. My running buddy had a 25 Johnson with the standard alum 3 blade prop (probably the one that came on it) running also on a 14' wooden boat. The Johnson was a lot more engine and as a result I went to and stayed with OMC for the next 30 years.

One teen on 2 skis is the best either boat could do.....but it was fun and "we're more concerned about pulling power for the water toys".

Mark