Quick question for the experts, I'm a noob

[VStarod]

I recently picked up a '79 Mark Twain 170 bow rider with a '77 Merc 1150 (Tower of Power) outboard. Boat weighs in at 1250lbs ... throw me, the wife and kids, toys etc. and a cooler of beer (light beer mind you) and we're probably weighing in at a modest 1,700lbs ish. Everything runs like a champ but my RPM's at WOT are about 4600 - 4700. The Merc has a 48 72762A-4 19p prop. So, I'm assuming it a 19" prop and was told that my RPM's at WOT should be between 5200-5600 for this motor ... so my question is, is the guy down the street trying to talk me into a new prop ?? He said I can damage the motor is the RPM's aren't high enough and it may be the prop ... Please give some advice to a new boat owner !!!! I know there's a bunch of factors that go into prop selection, but is a 19" about average for my setup. PS, we mainly just cruise and beach it ... I've only towed once and probably not do a whole lot more of it. Thanks

Rod

 

[VStarod]

Re: Quick question for the experts, I'm a noob

OK, so I've been reading, let me see if I got this right ... I currently have a 19 pitch prop and running 4600RPM at WOT, loaded ... if 1pitch less raises RPM 200 RPMs, then in theory, is I switch to a 17 pitch prop, I'll raise RPM's 400 RPM to 5,000 at WOT and since rpm range for the 1150 is somewhere between 5000 and 5300 (if this info I found is correct) that should do the trick ?? ... sounds right ??

Damn, I need a beer after this one ...

 

[sublauxation]

Re: Quick question for the experts, I'm a noob

In theory you've got it right. Depends on design of the new prop. I just bought a Turning Point 15 pitch that acts exactly like My Evinrude 17 pitch prop. Unfortunately that's not what I wanted. You using AL or SS? As far as AL props some on here like the Solas props, but the guy who fixes my props said to avoid both Solas and Turning Point. Of course he didn't offer up a great alternative. Try to find a place that will let you try out different props before committing. Hope that beer tasted good!

 

[walleyehed]

Re: Quick question for the experts, I'm a noob

Who ever told you to avoid Solas props is a man I would not take recomendations from as this tells me he doesn't sell them nor does he know them well enough to say anything...
The Hustler seems to be a good prop by design but I have seen several issues with pulling harder than they should if you're not willing to raise the engine up where they seem to run best-not trim-actually raising the engine a hole or 2, which I am all for when optimizing any set-up.
The vintage of the in-line 6's I set up have all been for 5800-6000. some say this is too much, I've found it's where they run best.
Don't be afraid of a Solas prop if going alum...they will carry a boat as well as any alum prop out there.
First thing I would look at or consider is the tach: is it accurate?? do we know the age of the tach?? If we know the tach IS right-not assume, but KNOW, then go from there. Decide whether you want alum or SS and go from there. The better the prop you choose the higher the engine needs to be. It's a stair-step proccess but it's the only way to really maximize your set-up for best performance.

 

[sublauxation]

Re: Quick question for the experts, I'm a noob

Finding the right prop is a bit of an art.

He didn't like Solas 3 blades, but did like their 4 blades, for whatever that's worth. I just found your post on the Solas props, I'm actually considering giving one a try. I don't mean to butt into this thread, but I raised my motor 1 hole higher and tried the Hustler prop, vents pretty bad on turns and no change in RPMs, does that mean it's raised to high or is that to be expected?

 

[walleyehed]

Re: Quick question for the experts, I'm a noob

sublauxation, PM sent to ya.

 

[sublauxation]

Re: Quick question for the experts, I'm a noob

VStarod
I'm fighting the same fight as you, close but not quite there on the prop. I've gone about every wrong direction so far, the good thing is I have a bunck of spare props now! Listen to what these guys say and they'll get you there, lots of variables to work with once you get into it!

Thanks for the message Walleyehed, that should help me get closer.

I didn't mean to specifically knock Solas props, especially since the guy I talked with didn't have anything specific to offer up as an alternative.