1969 20' engine choice

[Fr. Frank]

I once rigged for her owner a 20' CC, installing a 20" Merc 225 on a mechanical jackplate, with a low water pickup & nosecone. Cruised in the intercoastal at about 3800 rpm at 45 mph. Top speed was 62 mph at 6000 rpm running a 32" overhub chopper style prop.
The real story here? It was owned by 24 yr. old female attorney from Palm Beach who was given the boat by her Dad as a present for passing the bar exam.
It was fun to watch her flying down the waterway at 60 mph in a SeaCraft with a huge rooster tail behind her.

Do you need that much power? No, of course not. Sure is fun, though.

[eggsuckindog]

I think that would be a excellent choice, especially since I read the numbers above from the 175 ETEC, those are great #'s and I have a 200 Merc. Go to www.usavemarine.com and ask about the 150 ETEC, he is a big dealer and can ship it and give phone support if needed, might save some dollars but not sure where you are.

[finestkind]

Yea bill I'm not sure what pitch or prop size it has but I do need to find out because I ran a ground out at billingsgate at 9:30 at night(ouch)!!!!! Had to sleep the tide out and finally got off around midnight!!! LOLOL oh well Live and learn!!!!! The poor stainless prop didn't look so hot after that so I have to get a new one for this season!!! And yes I am too also watching the ultimate seafari! I think it's great the kid thinks like me!! Yes I do think it's a little high but hell only one way to find out!!! I myself am hoping ot make or get a hard top made for my boat I don't want it to high just high enough for me to stand up. I'm short so I only need it around 5'10. Once I have that then I can get up on top and see how it is!!! But I wish him luck with his creation !!!! I think it looks great (not to fond of the flat steering wheel though it doesn't look to cumphy)

[eggsuckindog]

They can fix your prop finestkind no problem, you don't need a new one

[finestkind]

Bill I told you that I didn't know the pitch prop I was running on my 115 suzuki. Well I found a guy that fixs props in Marston Mills, Cape Cod. When I took the prop off there was a 16 on the inside so I think it is a 16 pitch and I measured from the far outside of a blade across to the other and it was 12". So thats all I know about that I was just happy find the guy right near my house that fixes props!!!

[finestkind]

Thanks EggSuckingDog!!! I looked around and found someone 10 minutes from my house that fixes props!! So I thank you or else I probally wouldn't have looked to get it fixed. Probally wouldn't have bought a stainless one either! So soon enough I will have my stainless back!! I call it my East Sandwich Beach Prop!! Thanks again!!

[warthog5]

When I took the prop off there was a 16 on the inside so I think it is a 16 pitch and I measured from the far outside of a blade across to the other and it was 12". So thats all I know about that I was just happy find the guy right near my house that fixes props!!!

Is this a DF-115? They are designed to swing 14in dia prop's. If it's a factory Suzzy prop it will be a 14in dia. prop.

If it's a aftermarket prop, all bet's are off. The aftermarket guy's want to put smaller dia. prop's on them.

If it os a factory prop do NOT trust the marking's for the pitch.

Suzuki's always run less than they are marked. Don't ask me why. I don't know?

They can be as much as 2in of pitch less than what is stamped on the prop.

Alway's have your prop's check by a reputable shop before you make a change. You must know where you are, before you can know which way to go.
I use a shop that computer scan's the prop's. It's doesn't lie.

I have now had 4 Suzuki prop's checked and reworked.

The one's from last week that I bought were
2- Suzuki 14 X 20's RH & LH.

RH measured 19.1 pitch.
LH measured 18.7 pitch

They are now both 20 pitch.


The first one's I had were 14 X 18's RH & LH
RH measured 17 pitch
LH measured 16.7 pitch

They were both reworked to 18.5 pitch.

[oldbluesplayer]

Hey Warthog ... or anyone else -

Can you tell me what the expected result might be, of switching from an aluminum prop, to a SS, of the same pitch / diameter ?

Also, any general thoughts on the following - my old '83 115 Johnny shows 8000+ rpm on the tach, at WOT, but I don't believe that, or it would have blown up - but I also show, on my Humminbird FF, which tracks voltage, that my motor's charging system is putting out something like 16.5Vdc - which is seemingly way high, and I'm thinking the high voltage output is giving me a false tach reading... and without a true tach reading, trying to fathom the mysteries of correct propping is kind of pointless -

any thoughts, observations, clues to correction ?

just a note, from a long history of dabbling in motor performance, especially including 2 stroke motors, I pretty much know that rpm and power output are directly related to designed in breathing capability, volumetric efficiency, breathing thru the ports - that's why Im pretty sure this thing ain't pulling cleanly all the way up to 8000+... by design it would run out of breath and choke before then - two strokes usually go flat, in power output, once they go beyond their designed breathing/power point (so do 4 strokes, for that matter)and it hasn't blown up, not that I ever hold it at WOT, but have certainly cruised at well over 6000 rpm, with plenty of throttle left, so, that's were I'm coming from that my tach is bogus, and thus my ability to judge correct propping ???????????

all thoughts welcome !!

thanks
Bill

[eggsuckindog]

First you need to have the voltaged checked out,thats way too high, that will cook the battery's early. I agree its not going 8K, there are different settings on them, maybe your is on the wrong one say for a 6 cyl.motor. I believe there is a regulator on those rudes and it may be possible to do it yourself, I can't imagine it being too hard. If you feel adventurous to DIY, go to this site for the part www.usavemarine.com, now I'm not sure if you can, so I'll give you a phone number ask for Mike- tell him where you came from- and he'll help 727 938 9796- actually ask him about the tach too while your at it.

[Fr. Frank]

The tach should have a switch for the number of poles your alternator has. Ask a dealer what the setting for your tach should be. The voltage should not affect your RPM readings, as they're based on the number of times your power pack is fired or the number of times the trigger on your stator is activated.