Prop for mercruiser and fairly heavy 19' deep-V

[tmh]

OK, I've been here before learning about props and now I need some more specific help please. 1985 19' Mark Twain bowrider w/ mercruiser alpha one 305 2bbl 200hp V-8. According to all I've learned, my engine should be able to get into the proper WOT range (4200-4600 marked on engine) with a 19" pitch prop. However, I have been in the engines forum for a month or so going through one thing after another; tune-up. carb re-build, new fuel filter, plugs, clean hull, smart tabs, etc; to try and get more out of the engine. Although I have a few more things to check, the mechanic who worked on it doesn't think I'm going to get any more from the engine. So, it's either a bit "tired" or the boat is much heavier than i think - neither of which can I solve right now.

So.....back to the prop forum! I bought the boat with a 19P Black Max Aluminum prop. Got maybe 3700 rpm and 37 mph. I switched to a 17" SS prop (not sure which brand) and it upped rpm to 4150 and 40 mph or so. It rides much better with more boat out of the water with the 17" SS. Hole shot is OK. NOW, I'd like to try maybe a 15P prop. I'm looking for any specific recommendations on which prop(s) to consider. I was told at one time here that the "new" specs for my motor call for 4400-4800 rpm WOT, so, whether I use this or the spec marked on th motor 22 yrs ago, 4500 or so is a reasonable goal. This means 400-500 more rpm is fine as the 4150 I get now was with a lighter than normal load.

Anyone have a suggestion on which props to start looking for? I use eBay, Craigslist and new (only if I have to!!!! COST) so I'm open to suggestions.

 

[andy1canada]

Re: Prop for mercruiser and fairly heavy 19' deep-V

Howdy.

TMH...

Have you done a compression-test on your engine?

It seems to me that with a small-block in a 19-bowrider you should be busting 50+/mph without breakin' a sweat.

I would be certain the engine is up to snuff before I started trying different props.

Good Luck
Terry

 

[tmh]

Re: Prop for mercruiser and fairly heavy 19' deep-V

Andy, yeah, I know but I've had a good mechanic go over the engine and he doesn't see anything pointing to a power problem. Compression 130-(1), 140-(4), 150-(3) so that seems decent. He did full tune-up; carb rebuild, plugs, etc. It may just be a very heavy hull/waterlogged a bit. I can NOT see doing any more to eliminate waterlogged foam as i did floor over the winter and all that remains are some side areas that have floatation foam. It's just not worth digging into it any more.

So, I should be over-revving with the 17" but it's not. Therefore, I want to hear what 15" prop folks might recommend.

 

[Bry21317]

Re: Prop for mercruiser and fairly heavy 19' deep-V

I would say that your compression numbers are a problem. I have the same engine in a 19 foot crownline, its a 94 Chevy 305 with the 2bbl rochester carb, thru hull exhaust and I am pushing a 21pitch prop at 5200 rpms. So I am looking at pitching mine up higher, so bring the RPMS down.

Your Compression on all cylinders should be no greater than 10% on the highest and lowest. This is what I have always been told on here, so I am just restating it to you.

You might try running a Can of SeaFoam through the Gas tank to freeup any carbon in the engine. You can also run Seafoam, aerosol version (Deep Creep) through the Carb to really clean the inside of the motor up, then check the compression again. I would start here if your not getting all out of it that you need, but you should really be pushing a larger prop than a 15 on that motor.

I did put a 15 pitch prop on my last boat, which was a bayliner with a 125hp Force motor, 88 model, and that thing would blast out of the water and run about 38 with the 15 pitch. With the 17 pitch it would also come out very fast but get up to about 42. So any V8, should really be moving in a 19 foot boat.

The guy I purchased mine from said it would run mid 60s, but I don't think I believe that, as I have not had a chance to try it, but All I could get to was 50. But that was rough water, 1/2 tank of gas, alot of gear on the boat, and lots of beer, and toys. One day i will try to take it ot the lake by myself to see what it will really do.

I would keep on the engine, also make sure your Carb is opening all the way up, and there is not something kinking or stopping the throttle cable from pulling the butterfly all the way open. I had this happen on my Force and it would not give me all the RPMS.

Bryan

 

[Silvertip]

Re: Prop for mercruiser and fairly heavy 19' deep-V

I once owned a 19 ft Century bow rider with a 351 Ford. I had 17, 19, and 21P props but used the 19 almost exclusively. The 17 caused the boat to litterally jump out of the hole but overreved easily. The 19 was a 50+ prop. I have no idea how fast the boat would go with the 21. I was never on smooth enough water to really give let it hang out. I agree, the 305 should spin up with a 17 for sure. You either need a new mechanic or you really need to weigh the boat. You may be lugging around a couple hundred extra pounds of water. It is also possible that the lower unit was changed to one with a different gear ratio. It happens all the time.

 

[tmh]

Re: Prop for mercruiser and fairly heavy 19' deep-V

I don't disagree with what everyone is saying, but it does not help solve my problem. I have been over, around and through all the stuff that can effect my power because I know it should be performing better. I have been on these forums fr 1/2 year and did a ton of work to solve the problem.

However, whatever the problem, it is not going to be corrected any time soon, likely never. I WILL get the boat weighed, but it's in a slip for the summer and I may have it out in late July or so.

Be that as it is, I do need a 15" pitch prop based on current operating conditions. I wish I didn't, but I do. What I'm looking for is a prop type/brand that might work well for me.

 

[sabastianunf]

Re: Prop for mercruiser and fairly heavy 19' deep-V

Use the marine store on this website - thier prices on new props are pretty good. The least expensive will probably be an Amita solas. I haven't heard anything bad about them and they are only @ $100. Up from there you are looking at a Michigan Wheel or a Black Max but they are both a little more expensive. If you go with a Michigan Wheel you probably want to avoid the Vortex as they are pretty heavily cupped -for a better hole shot - but can load your engine a little more than the others. If you buy off e-bay or craigs list just make sure it is in good condition and has not been refinished or repaired as they will not be as strong as a new one. I agree with everyone else though - I have a 19' deep V with a cuddy cabin(see avitar) and a 120 hp mercruiser 4 cylnder and it will push a 17 pitch 3-blade without any problem. check your plugs for fouling - which will indicate a fuel and/or spark issue - since your compression is good - assuming you pull all the plugs before you did the test?

 

[bruceb58]

Re: Prop for mercruiser and fairly heavy 19' deep-V

Are you getting proper distributor advance? Have you measure the timing at 3000 RPM?

It is hard to compare what pitch one person is using vs another unless you both have the same drive and same gear ratio. For example, my last boat was a 20 foot cuddy, 305 Chevy 4bbl with a OMC Cobra drive. I swung a 17" prop at sea level and a 15" at Lake Powell and Lake Tahoe(3800 ft and 6000 ft respectively). The boat would do 42 MPH @ 4200RPM with the 17" prop.

Speaking of elevation...what is the elevation you are running at?

Are any of the props you are running cupped? A cup can add an inch to your effective pitch.

 

[walleyehed]

Re: Prop for mercruiser and fairly heavy 19' deep-V

I seen this coming and wanted to ask, but the last poster has a very important question....what "is" your elevation?
I'm having a problem with your numbers as well...yes, all hulls are different, even in the same model they vary to some extent, BUT, I have a 1985 Wellcraft cuddy(within a few inches of yours in length) with a 228 swinging a MWC apollo 19 at 4900.
I also ran a Merc Enertia 19 at 5050, a Solas Lexor in a 21P at just under 4700.......at 3600ft above sea-level.
If you are running below this altitude, have you verified the tach?
If it's accurate and the hull is slick and clean, you have some engine trouble that a prop will not fix.

 

[tmh]

Re: Prop for mercruiser and fairly heavy 19' deep-V

I am in the finger lakes NY State. About 600-800 ft. elevation I think, so not a big factor.

Bruce, what is "distributor advance"? I know the mechanic set the timing and checked the tach. My tach was off just a bit, but the numbers here are off his tach. Also, I verified speed with a gps yesterday and the speedo was maybe 1 mph high.

Walleyehead!!!!!! Haven't seen you here in a while! You are the one who got me going on all this last fall! Anyways, my Mark Twain boat may be pretty close to your Wellcraft in original weight - both built pretty solid with thick fiberglass if my info is correct. Although I do know the performance #'s here are without a slimed hull, my boat does have "worn out" bottom paint on it. However, I can't see how that would make much difference (until the bottom starts building up gunk).

Anyways, as I said, I'm kinda stumped for what else to check engine wise. I do have a call into the previous owner to see if my performance is below what he used to experience - or when the #'s started to fall off. he's a good guy and will tell me what he knows at least.

Thanks for all the help! I'll keep plugging away.

 

[tmh]

Re: Prop for mercruiser and fairly heavy 19' deep-V

OK, I'm going to try to post a link to my latest thread in the sterndrive Engines forum for more background - I know Walleyehed for one hasn't been active on the board for a while so my issues may be new to some.


http://forums.iboats.com/showthread.php?t=197225

I have a few older threads here and in that forum also about these issues...I start a new thread when I change information much, such as having donne the carb, plugs, etc.

Please...I DO want guidance on this. Maybe another new prop is just a bandaid, but one I may need to use short or long term, depending if I ever find the "cause".

I forgot to check the fuel filter and water seperator (don't even know where it is, but never really looked for it) when I was at the boat earlier today. Crap. I kinda assume the mechanic would have quickly checked these items during his latest tune-up and carb re-build work on it. However, I guess i shouldn't assume anything and just go thru the list of "possibilities" until I am out of ideas from here!

Thanks as always for the informed help.