New to me Crestliner Voyager 15 prop pitch question

[baconbiscut]

I'm back on the forum again its been a while. I recently purchased a late fifties vintage Crestliner Voyager 15, the guy I bought it from put a 1963 65hp Merc inline 4 on the back and I don't think that the boat,motor, and prop combination are correct. I don't have a tachometer set up so I don't have any real numbers for you guys. Currently the engine has a 21 pitch three blade aluminum prop on it, based on the knowledge of you guys here in theory does this sound about right or wrong for my size boat. Attached is a photograph to you give you guys an idea of what I'm working with here

Thanks, Dan

 

[steelespike]

I think your gear ratio is 2.00 I think the 21 is way too much prop.
I have a 57 Bucaneer 18 with a 65 Merc 500 1.64 ratio 1000 lbs all up weight it runs an 11 or 12" pitch.
Your 65 with a 2.00 will let you have a little more prop but I think 21 is too much.
You could get a Tinytach, let them know its going on a multi cylinder.
Use the bottom cylinder and get the wire outside the cover to avoid stray pulses.
In the mean time a lightly loaded wot run for a gps speed will get us started.
I'm guessing you will end up with a 15 or 17" prop.
There is a retro Crestliner site that has lots of info and catalogs.
I'm guessing yours is a 58 or 59.

 

[baconbiscut]

I actually had the boat out this morning before work, at wide open throttle with just me in the boat, I got 27mph on the gps. The motor doesn't sound like it's getting up to full speed though. I guess these mercs have a lot of torque...

I will have to look into the tiny tach for sure btw.

 

[baconbiscut]

Well I Just purchased a prop off of iboats tonight, it should be coming in the mail on Wednesday. I went ahead and blindly ordered a Solas Amita (cheapest prop there was) 17 pitch by 13 1/4". I wrote down my serial number for my engine it was a 17xxxx number I can't remember what the rest is, I lost the piece of paper that I wrote it down on. I believe it dates it somewhere between 64-65, though who knows. Does anybody have an idea of what to expect RPM wise for these four cylinder mercs at WOT?

Also, will I need a thrust washer for this prop? Or can I remove old one and reuse the hardware?
Dan

 

[steelespike]

According to my after market manual the Merc 650 appears in 63 and runs through to 66 .2 7/8 bore and 2.3 stroke 60 cu. in. 65 hp at 5200 rpm
Bore and stroke change in 67 to 2 15/16 X 2.3. 62.42 cu in. Some 67 up may have electronic ignition. no breaker points.

 

[baconbiscut]

Okay, so I have some numbers, With just me in the boat at WOT I was running 3250 rpm at 26-27 mph.

 

[steelespike]

Using 2.00 ratio,3250 rpm,27 mph,21" prop calculates at 16%.slip fairly normal for a prop that is way too much.
Problem is you need to make up 2000 rpm So we may have a tired or poorly running motor as well as a prop selection problem.
Some things to check;Compression check,timing set right and advancing as it should,Throttle opening as it should,All cylinders firing as they should.
You wouldn't be the first to not realize you are missing one or more cylinders except for the lack of power.
Is the motor trimmed right and weight balanced well?
If your sure about the motor and the setup My guess for a prop would be a 15".

 

[baconbiscut]

The engine has 145lbs of compression on each cylinder, this was on a cheap gauge nonetheless. Throttle is set, the timing on the engine could be an issue, out on the water I accidentally fiddled with the timing advance set screw. However performance difference was negligible. I believe I'm getting fire on all cyclinders otherwise I doubt the boat would even plane. I think I have two issues though. A motor that is overpropped and needs to have the timing tweaked. I'll have to get a timing light tomorrow. Today though I should have a prop, I'll see if I can get some results posted today.