New prop recommendation

[mr300z87]

Hi all,

I usually spend my time in the boat restore and mercruiser forums, now I need some assistance here. I own a 1990 sea ray sundancer 250 powered by a 7.4L carb, bravo 1, on the 4th we went out with a full load of people and stuff for fun and fireworks. She struggled to get on plane but once there was running fine. The all of a sudden it was like she shifted into neutral. We had no forward propulsion above 1500 rpm. I figured the prop hub failed from the stress of the heavy load. BTW I bought the prop on ebay 5 seasons ago. The prop was a Mercury Mirage 17 pitch which is listed as oe for a 90 250 Dancer on Sea Ray's website. Performance was good. 25 - 27 mph 3400 rpm.

Yesterday while still in the water a swapped to a spare 17 pitch aluminum prop that was on the boat when I got it, of course I forgot to record the mercury part # before installing it. BTW, I never ran the boat with this prop since the engine and drive were shot from hurricane sandy damage. See thread in signature. This fixed the issue so the boat is usable again and note I have no plans to pull boat out until fall. Launch performance with light load 2 adults was OK however my cruise speed at 3400 was 22 - 24 mph slightly slower than the mirage 17. I did not do a WOT with this prop but the mirage would hit 4300 RPMs maybe slightly higher in optimal conditions.

I would like to upgrade to a newer technology propeller, most of our cruising is light to medium load of 2 to 4 adults. The props I have been looking at are the mercury mirage plus, turning point ss, and Michigan wheel ss. Reccomendations from the experts would be greatly appreciated. I hope I have included enough information, but feel free to let me know if more is needed.



Mike

 

[Starcraft5834]

If you have a 3 blade prop on that, consider switching to a 4 blade prop, that's a pretty heavy boat. 4 blade would offer better hole shot, get on plane at mid range speeds easier... I'd put a 17p 4 blade on it and see what numbers you get. you'll notice difference getting on plane faster..

 

[mr300z87]

So I am considering Solas HR Titan 4 blade or Turning Point Express Mach 4 or Mercury Mirage Plus (these are pricey) 3 blade. It is my understanding, when upgrading to a 4 blade prop the pitch should go down 2". The failed prop and aluminum spare are both 17 pitch so if I upgrade to 4 blades do I go to 15" pitch or stick with 17"?

I also spoke to a local Prop Shop who said my old Mercury Mirage can be repaired. I may do this regardless.

With all that said is the investment in a 4 blade worth the expense? I do not think going with a new expensive Mercury brand prop gives me any gains at all.

My goal here is to have a decent hole shot and good mid range cruise speed. This is no performance boat so top end speed is not important.
All recommendations are greatly appreciated.

Mike

 

[Sea Rider]

What's the min-max wot rpm range factory stated for that motor ? need to dial a 4 blade prop that will rev towards its max wot rpm range with 4 adults on board, when with 2 just throttle less not to over rev. Once there can throttle at your preferred cruising speed...

Happy Boating​

 

[Scott06]

So I am considering Solas HR Titan 4 blade or Turning Point Express Mach 4 or Mercury Mirage Plus (these are pricey) 3 blade. It is my understanding, when upgrading to a 4 blade prop the pitch should go down 2". The failed prop and aluminum spare are both 17 pitch so if I upgrade to 4 blades do I go to 15" pitch or stick with 17"?

I also spoke to a local Prop Shop who said my old Mercury Mirage can be repaired. I may do this regardless.

With all that said is the investment in a 4 blade worth the expense? I do not think going with a new expensive Mercury brand prop gives me any gains at all.

My goal here is to have a decent hole shot and good mid range cruise speed. This is no performance boat so top end speed is not important.
All recommendations are greatly appreciated.

Mike

If you want hole shot and mid range cruise I think you would like a 4 blade. That plus stern lift is why I have run them on my last two boats.

WOuld need to know your WOT with the mirage but I would think the mirage would bite enough that you may not loose as many rpm with a 4 th blade as typical. If you are in the upper side of WOT rpm range with a 17" mirage maybe try a 16" michigan vortex 4 blade. I had every good experinces with them and its like a $150-180 buy in... Yes you can get your mirage fixed for about $180 maybe 200

 

[mr300z87]

FYI I stated my WOT with the Mirage in my first post. Spec for my engine is 4200-4600 so at 4300 I am in the range. I will almost never run the boat at these RPMs. I could afford a few more RPMs on the top end though.

 

[QBhoy]

I think you’ve hit the bottom when you first had the rpm drop. Typical sign of a spun prop hub

 

[mr300z87]

So I have been running with my spare aluminum prop now for the month of July all has been good. I had a new hub installed in my Mirage and I am headed now to do my 2nd in water prop swap. The prop was repaired by Atlantic Prop in Edison NJ for $100.00. Super nice guy and highly recommended for prop work in central NJ. Hope all goes well.

 

[mr300z87]

The swap back went great, gained the 3 mph at cruise speed I lost with the aluminum spare prop. All is well. Thanks again to Atlantic Propeller. I still may purchase a 4 blade 15 pitch to see if there are any gains in cruise speed. Don't care much about WOT speeds as I will almost never go there. Have a great day.

 

[Scott06]

The swap back went great, gained the 3 mph at cruise speed I lost with the aluminum spare prop. All is well. Thanks again to Atlantic Propeller. I still may purchase a 4 blade 15 pitch to see if there are any gains in cruise speed. Don't care much about WOT speeds as I will almost never go there. Have a great day.

Others will disagree but I am a big fan of 4 blades, on my last two boats improved holeshot stern lift and lowered planning speed. I dont have a big enough boat or go far enough to comment of fuel efficency at crusie etc.