prop tweeking, asking to much

[fbinker]

My question is,I put a new 4 blade alum. 14.5 x 18pitch prop on last night, tried it today. 4400 RPM 40mph GPS. 2 people in boat 1 adult 205lb 1 child 65lb played with the trim and that was the max speed. about 7 seconds to plan, comes off plan at about 21 mph. not looking to go 55mph but 46-47 would be great. will be pulling kids this summer on tube. Maybe I need a 3 blade stainless for speed. 4.3 mercrusier 1998 52 hours on motor. O ya, my last prop was a 14.5 x19pitch 3 blade 4200rpm 41mph GPS. thanks for all the help.

 

[freddyray21]

Re: prop tweeking, asking to much

how big of a boat?

 

[steelespike]

Re: prop tweeking, asking to much

You did a pretty good job with your info but just to help you understand props and the info we need read the stickies at the top of the page and go to the prop store and read the helps at the top and bottom of the page.
Generally a 4 blade is not the choice if your looking for more speed.A 4bld
will improve low end performance at a slight loss of top end.
We need to know the brand,size and weight of boat if possible.
Read up on the Turning point Hustler props.Close to stainless performance
at aluminum prices.

 

[180shabah]

Re: prop tweeking, asking to much

If the engine is running well, then it looks like you were over propped to start with. You need to drop down 2" in pitch to compensate.

I also recomend the Hustler/Legacy prop. It really is as good as the marketing claims - pretty rare these days.

 

[tmh]

Re: prop tweeking, asking to much

A 3bld stainless 18-19" might get you 2-3mph on top end. However, I doubt ANY prop can turn the numbers you have now into 46-47mph WITH good low end for tubing. You may need to compromise and be satisfied.

 

[180shabah]

Re: prop tweeking, asking to much

A three blade SS prop is going to lug his engine even more than his current aluminum prop, they tend to be more aggressive than aluminum designs. He would need to drop pitch probably all the way dow to 16" or so, to get the engine back into it's power band.

We still don't know what boat we are dealing with, but assuming a drive ratio of 1.65, he is getting an 11% slip with both props. His speed and RPM results at least are consistant with each other. So no matter how you slice it he is currently over-propped.

I just don't see the need to waste money for SS on an "everyday" boat where absolute top speed is not the primary concern. Again, I will throw out a plug for the Hustler. It has more rake and cupping than typically found on aluminum props. It really does "bite" into the water, so you have much less ventiliation, especially in turns(which he will be doing with the tube this summer). It is also the only aluminum prop on the market that is vented, this allows exhaust gasses to "leak" in front of the blades, increasing initial slip and improving hole shot. may not need the 4 blader for watersports, it really is the best all-around prop on the market, IMHO.

I have no financial interest in TR propellers, just think the developed an awsome product. I still carry a Hustler as my shallow/unfamiliar water prop.

 

[fbinker]

Re: prop tweeking, asking to much

Sorry about that, the boat is a 1998 Mariah 180 Shabah. the weight is about 3000lb I think. thanks again.

 

[JJJ]

Re: prop tweeking, asking to much

A great pulling prop is the Solas Amita 3 in the big 15.3 diameter version.
I run a 15.3 X 19P in my 20' cobalt 4.3 stock 4bbl, turn 4800 rpms at 48 mph or so.

 

[180shabah]

Re: prop tweeking, asking to much

Sorry about that, the boat is a 1998 Mariah 180 Shabah. the weight is about 3000lb I think. thanks again.

Something isn't right. I have the same boat ('cept mine is a '96) and 3000lbs is pretty close with fuel gear and 2-3 passengers. I had no problem spinning my 21" hustler to 4800RPM. I am currently running a 23" SS and still turning 4400 RPM's. If you have the 1.65 ratio, then your performance with the 19" should have been close to what I get with a 21"er.

You need to start looking for more power. When was the last full tune up done? Have you compression tested the engine? Are your water shutters still in the top of the y-pipe, or have they fallen down into the drive?

 

[fbinker]

Re: prop tweeking, asking to much

had a tune up last week, new plugs, cap & roter, oil change, lower unit syn. oil, impeller. Boat only has 50 hours on motor. the last 4 years was used 4 hours, the gas is from last year would that make a big difference.