New prop for my 3.0 mercruiser results

[Lager]

My 1990 mercruiser 3.0 bowrider came equiped a 19 inch 3 blade prop.
On accel from Idle, engine bogged a bit, took a bit to come out of the hole onto plane.
At 3000 rpms, it runs a fuel efficient 30 mph and felt light , but on turns felt sluggish and boat lost speed.
Top speed was 43 MPH @ 4300 RPM. On this engine max RPM's are supposed to be 4200-4600 .
Since Im interested in pulling skiers, I bought the Solas Amita prop for sale here. Its the same diameter as I had ,but a 17 inch pitch 4 blade and this what I have found.
On accel from idle, it takes right off and no signs of bogging. The 4 blade also is more responsive to the trim button, like it connects to the water better.
At 3000 rpms is now 23 mph and boat feels sluggish and not on plane completely. Im sucking up fuel and not getting anywhere.
Max rpms are now 4600 for a top speed of 36 MPH.
When cornering with the 17 inch 4 blade it still feels like it hooked to the water so thats a plus.
Im glad I bought the 17 inch 4 blade, when Im pulling the grandkids it will work great.
When Im heading out to do some fishing, cover some water distance I can always pop on the 19 inch 3 blade. Its easy enough.
On this boat, there is no one prop that is good for everything. There is always a trade off. Im sure you find the same results.

 

[jestor68]

Re: New prop for my 3.0 mercruiser results

How were/are you measuring speed?

I ask because with a 1.98 gear ratio(standard with a 1990 3.0L), a 19 pitch at 4300 rpm equals a theoretical 39 mph, not figuring in any slip yet. How were going 43 mph?

The 17 pitch at 4600 rpm equals a theoretical 37 mph; something less with some slip figured in.

Since you were getting 4300 rpm with the 3 blade, I might have recommended the 18 pitch for a 4 blade to maintain roughly the same WOT rpm and speed, but still gaining better hole shot and grip under just about any circumstance.

Not that you're doing bad with the 17 pitch.

 

[Maclin]

Re: New prop for my 3.0 mercruiser results

Not sure of the boat you are using, but it may benefit from some Smart Tabs. I bet it could plane sooner and stay on plane at slightly lower speed, kind of their thing.

Bennett and other MFG's also have some automatic type tabs.

 

[eavega]

Re: New prop for my 3.0 mercruiser results

Thanks for this post. I have a 1988 Mercruiser 3.0 on a 17' Stingray. I normally run a 20P SST, which gives me a top speed of 38 MPH at 4200 RPMs, but hole shot is a bit wanting. I've tried a 19P Aluminum with no improvement in my WOT RPMs, so to nudge my RPMs to the top of the band, improve the hole shot, and hopefully correct a slight tendency to porpoise (which keeps me from really getting the trim right at WOT) I also have purchased the 17P Solas Amita 4-blade (right here on iBoats!), but have not had an opportunity to run it and see if I get what I was hoping for. I should finally be putting it on the water this week, so I'll report back my numbers on Friday. I figure I am going to have to keep two props depending on what the water plans are for that day. I was really hoping to keep the 4-blade as the "regular" prop, since most times the lake is a bit too rough to open it up wide.
If the 4-blade doesn't help me out any, then I am going to go with smart tabs. I was trying to avoid installing them because on my last boat they tended to interfere with the rear boarding ladder, and folks would end up putting a foot on them when climbing back into the boat.

Rgds

Eric

 

[Starcraft5834]

Re: New prop for my 3.0 mercruiser results

Thanks for this post. I have a 1988 Mercruiser 3.0 on a 17' Stingray. I normally run a 20P SST, which gives me a top speed of 38 MPH at 4200 RPMs, but hole shot is a bit wanting. I've tried a 19P Aluminum with no improvement in my WOT RPMs, so to nudge my RPMs to the top of the band, improve the hole shot, and hopefully correct a slight tendency to porpoise (which keeps me from really getting the trim right at WOT) I also have purchased the 17P Solas Amita 4-blade (right here on iBoats!), but have not had an opportunity to run it and see if I get what I was hoping for. I should finally be putting it on the water this week, so I'll report back my numbers on Friday. I figure I am going to have to keep two props depending on what the water plans are for that day. I was really hoping to keep the 4-blade as the "regular" prop, since most times the lake is a bit too rough to open it up wide.
If the 4-blade doesn't help me out any, then I am going to go with smart tabs. I was trying to avoid installing them because on my last boat they tended to interfere with the rear boarding ladder, and folks would end up putting a foot on them when climbing back into the boat.

Rgds

Eric

Interested in report when you put the 4 blade on 17p.. thinking that gonna put your engine rpm's in a 4500-4600 "sweet spot", your top end will drop a few mph.... I bet you keep the 4 blade on for every day use...... and have the 3 blade as a back up.... incase your 4 blade falls off

 

[Lager]

Re: New prop for my 3.0 mercruiser results

How were/are you measuring speed?

I ask because with a 1.98 gear ratio(standard with a 1990 3.0L), a 19 pitch at 4300 rpm equals a theoretical 39 mph, not figuring in any slip yet. How were going 43 mph?

The 17 pitch at 4600 rpm equals a theoretical 37 mph; something less with some slip figured in.

Since you were getting 4300 rpm with the 3 blade, I might have recommended the 18 pitch for a 4 blade to maintain roughly the same WOT rpm and speed, but still gaining better hole shot and grip under just about any circumstance.

Not that you're doing bad with the 17 pitch.

Jestor, I cant argue with your figures. But its true, I measured my speed using my GPS, both times since my boat speedo does not work and im not looking to fix it cause they are usually very inaccurate.
Now that you brought up the 18 pitch, yeah, I should have probably bought that prop instead.
I do like the 4 blade, the difference is very noticeable, just wish I had more speed behind it. A few MPH might not seem all that much but its make all the difference in the world in the way this boat rides in the water and big difference in fuel economy .

 

[Lager]

Re: New prop for my 3.0 mercruiser results

Not sure of the boat you are using, but it may benefit from some Smart Tabs. I bet it could plane sooner and stay on plane at slightly lower speed, kind of their thing.

Bennett and other MFG's also have some automatic type tabs.

Thanks for your post Maclin, If I was was going to keep this boat? I might consider them. But , I have already found out that i dont have enough boat to do what I want to. No sense in dumping more money into this hole in the water.

 

[Lager]

Re: New prop for my 3.0 mercruiser results

Thanks for this post. I have a 1988 Mercruiser 3.0 on a 17' Stingray. I normally run a 20P SST, which gives me a top speed of 38 MPH at 4200 RPMs, but hole shot is a bit wanting. I've tried a 19P Aluminum with no improvement in my WOT RPMs, so to nudge my RPMs to the top of the band, improve the hole shot, and hopefully correct a slight tendency to porpoise (which keeps me from really getting the trim right at WOT) I also have purchased the 17P Solas Amita 4-blade (right here on iBoats!), but have not had an opportunity to run it and see if I get what I was hoping for. I should finally be putting it on the water this week, so I'll report back my numbers on Friday. I figure I am going to have to keep two props depending on what the water plans are for that day. I was really hoping to keep the 4-blade as the "regular" prop, since most times the lake is a bit too rough to open it up wide.
If the 4-blade doesn't help me out any, then I am going to go with smart tabs. I was trying to avoid installing them because on my last boat they tended to interfere with the rear boarding ladder, and folks would end up putting a foot on them when climbing back into the boat.

Rgds

Eric

Have you considered adding one the available fins that attach to your lower end like a Doel fin or some sort of hydrofile thats out there?Ive had them on all of my boats and seem to give better leverage to your lower end which makes your trim less sensitive. Just an idea.
Just to warn you, I just put the same prop you just bought on my 3.0 Mercruiser and had trim a big chunk out of my anode to make it fit with out hitting.

 

[eavega]

Re: New prop for my 3.0 mercruiser results

Have you considered adding one the available fins that attach to your lower end like a Doel fin or some sort of hydrofile thats out there?Ive had them on all of my boats and seem to give better leverage to your lower end which makes your trim less sensitive. Just an idea.

I had one on a 50 HP outboard on a tri-hull boat a few years back. The previous owner had put it on. It lasted two trips on my boat. I found the Doelfin did help to get up on plane a bit easier but it tended to fight me on turns in a way that I found rather frightening if the boat was moving at higher speed. Mind you the motor had manual tilt, so I don't know how it feels on a motor where you can vary the trim angle, but with the fixed angle I felt some loss of control in turns. On that boat, I went with the Smart Tabs, and found that I had the same assistance with getting up on plane, but without any of the odd steering effect. Only problem with the smart tabs was where they fit on the boat tended to interfere with the boarding ladder.

Just to warn you, I just put the same prop you just bought on my 3.0 Mercruiser and had trim a big chunk out of my anode to make it fit with out hitting.

I've already put the prop on the outdrive to check proper fitment. It clears the anode fin easily. I suspect that the boat came originally with the cutout anode trim fin. The prop it came with had about the same diameter as the Solas prop. Since my SST prop has more pitch it actually leaves less clearance on the anode than the Solas 4-blade.

 

[Maclin]

Re: New prop for my 3.0 mercruiser results

Thanks for your post Maclin, If I was was going to keep this boat? I might consider them. But , I have already found out that i dont have enough boat to do what I want to. No sense in dumping more money into this hole in the water.

Well shucks, I was hoping I could help spend some of your money

Good luck!

 

[Lager]

Re: New prop for my 3.0 mercruiser results

Well shucks, I was hoping I could help spend some of your money

Good luck!

:lol:
Thanks for trying to help.

 

[Lager]

Re: New prop for my 3.0 mercruiser results

I had one on a 50 HP outboard on a tri-hull boat a few years back. The previous owner had put it on. It lasted two trips on my boat. I found the Doelfin did help to get up on plane a bit easier but it tended to fight me on turns in a way that I found rather frightening if the boat was moving at higher speed. Mind you the motor had manual tilt, so I don't know how it feels on a motor where you can vary the trim angle, but with the fixed angle I felt some loss of control in turns. On that boat, I went with the Smart Tabs, and found that I had the same assistance with getting up on plane, but without any of the odd steering effect. Only problem with the smart tabs was where they fit on the boat tended to interfere with the boarding ladder.




I've already put the prop on the outdrive to check proper fitment. It clears the anode fin easily. I suspect that the boat came originally with the cutout anode trim fin. The prop it came with had about the same diameter as the Solas prop. Since my SST prop has more pitch it actually leaves less clearance on the anode than the Solas 4-blade.

Im sure you figured out that having an adjustable trim makes a big difference as compared to non adjustable. To tell you the truth, I never removed my fin off any of my boats to see if there was a difference. I just trim down a bit to set the hull a little lower in the water before I attempt a sharp turn and thats where i noticed a big difference with the 4 blade. It seemed to stay hooked to the water providing better forward drive compared to the 3 blade. Its going to be interesting on what you think of it on your boat.

 

[eavega]

Re: New prop for my 3.0 mercruiser results

As promised, I ran today with the 4-blade 17 P Solas Amita. My numbers were as follows:

WOT RPM = 4500
Max Speed = 37
On Plane time = ~ 4 sec.
Min plane speed 9 MPH.

I don't know how 4 blades would affect slip calculations. I had read that 4-blade will reduce slippage, but per the number I have here, I have 0% slippage, which doesn't sound right.

So I gained my desired RPM, lost one MPH top-end speed, and my time to plane was great. You could really feel the boat jump out of the water. I think this has now become my everyday prop.

Rgds

 

[Lager]

Re: New prop for my 3.0 mercruiser results

Glad it worked out good for you !
Did you notice any difference in cornering like I did?
Mine seemed to reduce prop slippage or blow out and didnt lose much speed as compared to my 3 blade.

 

[Starcraft5834]

Re: New prop for my 3.0 mercruiser results

As promised, I ran today with the 4-blade 17 P Solas Amita. My numbers were as follows:

WOT RPM = 4500
Max Speed = 37
On Plane time = ~ 4 sec.
Min plane speed 9 MPH.

I don't know how 4 blades would affect slip calculations. I had read that 4-blade will reduce slippage, but per the number I have here, I have 0% slippage, which doesn't sound right.

So I gained my desired RPM, lost one MPH top-end speed, and my time to plane was great. You could really feel the boat jump out of the water. I think this has now become my everyday prop.

Rgds

nice call!!,, sounds like you found the right prop enjoy!

 

[eavega]

Re: New prop for my 3.0 mercruiser results

Glad it worked out good for you !
Did you notice any difference in cornering like I did?
Mine seemed to reduce prop slippage or blow out and didnt lose much speed as compared to my 3 blade.

The 20P SST never blew out on corners for me unless I was trimmed WAY up, but what I did notice is that at a WOT and trimmed up correctly, the steering seems to require a bit more effort, almost like the LU wanted to stay pointing in whatever direction it was in. Also had a tendency to wander to starboard if you released your grip on the helm. Don't know if a repositioning of the trim anode is warranted.

One additional plus is that the boat tracks really well at idle speeds. This is a known problem with Stingrays and I had noticed it when docking or loading onto the trailer.

Rgds

E

 

[Lager]

Re: New prop for my 3.0 mercruiser results

Sounds like you made the right choice. Enjoy it.

 

[steelespike]

This is a long dead thread you will get more direct results if you start your own thread.
There is a tab at the top of the main prop page.
While a prop change may be indicated we do need to try to figure out if the tach is accurate.
Can you get us your lightly loaded wide open throttle gps speed?