Prop question on Mercury Classic 50

[alanpeters]

I have a 1987 Mercury Classic 50 on a 1987 16' Crestliner Angler fishing boat, tiller configuration, that I bought second or third hand. The boat is fiberglass and fairly heavy. It has a 17 gallon gas tank under the floor. I weigh about 260 and mostly fish alone. I've owned the boat for about 10 years and unfortunately only get on the water a few times per year.

The prop on the boat is an aluminum 3 blade and the only marking visible while installed it is stamped on its body: "PA X 337". Can any one tell me what size and pitch that is?

With this prop, the hole shot is poor but once on plane the boat runs over 30 mph, as high as 35 mph on flat water. The hole shot issue is especially true if I have a passenger or I am facing the wind. I would trade some speed for better acceleration.

Second question. At some point, the prop got damaged and I had it rebuilt. The prop is beat up again and while it works, I am now debating another rebuild or getting a new one. While at a remote location that trip I bought a prop from a local marine place that was supposed to be close to what they thought I needed but I never installed it. It is made by Michigan Propellers with the number 031017 stamped on the inside hub. The box has that same number on it and says it is 10.375 x 13. I am wondering if this is really appropriate for my boat. I am also wondering if this prop would improve my acceleration over the current one or just add to the problem. From what I have read, it sounds like 13 might be too high a pitch.

As this is a tiller, I don't have a tach on the boat and do not know what the rpm is at WOT. If it turns out I really need that information, what is my best bet to get that inexpensively. Is there something I can clip on the motor just for testing? I prefer to not install anything permanently.

Last question, kind of unrelated. I am going to the lake soon and checked the lower unit lube yesterday and it was very black.I decided to drain it down and then put in a whole 10 ounce tube of marine lube, but it was not enough to raise the level to the vent. It didn't seem that more than 10 ounces came out, but maybe it was just low to begin with. What is the capacity of the lower unit? Thanks.

 

[Watermann]

I have a 55 HP Johnson and run a 13'p on it, it should do very well, sounds like you need to just slap it on there and give it a try. You'll probably then be able to see the diameter and pitch numbers on the old prop underneath the prop nut and washer.

10 oz isn't enough as you know, really you should fill the lower unit until the gear oil starts to run out of the vent hole.

 

[roscoe]

Welcome to boats.


Sorry, can't find a cross reference for your pax337 prop.
A good prop repair shop would be able to measure the prop you have.

Your first task is to replace the prop with the one you have, 10.375 X 13.
It may be the answer to your problem.
If not, you will know how it performs and have additional info to work with.

I have had similar boats, and in my opinion, a 10 x 13p prop is very close to what you will need.
You may even need to drop down to an 11p prop if your boat is carrying extra weight.
Remember, you have an older motor, which is likely only putting out 40 hp at this time.

A tinytach or similar inductive tach will work for you.
You just need to wrap the signal wire around a sparkplug wire.

Don't have my manuals with me right now, but I believe that gearcase requires about 14 ounces of lube.
Fill it before running it.

Report back after testing that Michigan Wheel prop.

 

[steelespike]

There may be numbers under the prop nut.
I think the 13 is probably too much prop, I think a 11 or 12may be closer to what you need.
Put the 13 on and see how it runs,you need to see under the nut anyway.
There has been a lot of success with the induction tachs.If you wrap the lowest plug wire
and get it outside the cowl you may avoid stray pulses from the other plug wires.

 

[jestor68]

The 13 pitch prop you have is (the first prop listed) on the list of recommended props by the Merc prop selector.

Get the 32oz bottle of gear lube and the pump. Your lower unit should hold around 15-20 oz.