1986 5.0L 200HP Mercruiser RPM range?

[b.lee]

What kind of RPM's should I be seeing out of my engine?

1986 Four Winns Brougham 190 5.0L 200HP Mercruiser w/ Mercruiser outdrive
Came stock with 14.5x19 3 blade prop,
I stuck a 14x19 4 blade prop on it since the original one was a little beat up.

I searched and I can't believe there aren't more topics about this...

Saturday I was at the lake, and only hitting about 3500 rpm
Then later on in the day it was only getting 3100 rpm

I got home, replaced the plugs, wires are like new and still very flexible.
I think I might replace the cap and rotor next? (probably wires too at the same time for good measure)

I know the prop I put on might cause a little RPM loss, but what should the boat do in stock form, RPM wise?


Note: The entire fuel system is brand new, except for the fuel pump (mechanical pump, looks newer, may have been replaced by the previous owner)

The old plugs didn't look too bad either.

 

[b.lee]

I just found this... is this the right info for my specific 1986 5.0L 200hp?
https://www.perfprotech.com/blog/tec...specifications

Maximum rpm @ WOT3

4400-4800 rpm

And what's WOT"3" stand for... I know what WOT stands for.. what's with the 3 at the end?

 

[Bondo]

What kind of RPM's should I be seeing out of my engine?

Ayuh,.... Welcome Aboard,..... Ya oughta be seein' 4200/ 4600 rpms at Wot with a 2bbl. carb,....

'n 'bout 4400/ 4800 rpms at Wot with a 4bbl. carb,....

With the proper pitched prop installed of course,....

 

[nateo]

This bad boy is in sticky:
http://forums.iboats.com/forum/engi...6-list-of-possible-causes-of-low-wot?t=295070

What is your idle rpm in neutral on muffs and idle rpm in neutral in water? depending on those numbers and if you want to fix her yourself then you may want to start with a compression test on all 8 and also check timing. What carb do you have?

 

[Watermann]

You normally have to drop pitch by 1" p when going to a 4 blade and the prop selector here at iboats doesn't recommend using a 4 blade for your type of boat, it recommends the 3 blade. Also is your new prop made of SS or AL? Your old prop probably didn't have nearly the cupping or as aggressive rake like the newer props have that grab the water better which can also lower RPMs.

The Quicksilver Black Diamond prop I have now is probably the best I've used.

 

[biggjimm]

And what's WOT"3" stand for... I know what WOT stands for.. what's with the 3 at the end?


The "3" means look at the notes below the chart & note #3 is applicable to that particular information in the chart. Jim.

 

[Alumarine]

What rpm's were you getting with the old prop?

 

[b.lee]

Ayuh,.... Welcome Aboard,..... Ya oughta be seein' 4200/ 4600 rpms at Wot with a 2bbl. carb,....

'n 'bout 4400/ 4800 rpms at Wot with a 4bbl. carb,....

With the proper pitched prop installed of course,....

Thank you and yes 2 barrel carb, freshly rebuilt.

I've read this 14x19 4 blade will drop my RPM's approximately 400 rpm
If thats true sounds like I should be seeing 3800-4200 RPMs... Last weekend I was only getting 3100-3500 RPMs

This bad boy is in sticky:
http://forums.iboats.com/forum/engi...6-list-of-possible-causes-of-low-wot?t=295070

What is your idle rpm in neutral on muffs and idle rpm in neutral in water? depending on those numbers and if you want to fix her yourself then you may want to start with a compression test on all 8 and also check timing. What carb do you have?

Thanks for the link to the sticky
I'm unsure of my idle on muffs or in the water, I'll check soon
I will do a compression test soon as well, I just changed all the plugs and they looked good.. no black oily plugs or anything.. all were nice light chocolate color

I'm unsure of what carb I have, I do know it is a 2 barrel. How can I tell which make/model carb I have?

You normally have to drop pitch by 1" p when going to a 4 blade and the prop selector here at iboats doesn't recommend using a 4 blade for your type of boat, it recommends the 3 blade. Also is your new prop made of SS or AL? Your old prop probably didn't have nearly the cupping or as aggressive rake like the newer props have that grab the water better which can also lower RPMs.

The Quicksilver Black Diamond prop I have now is probably the best I've used.

Yeah I know I should have dropped the pitch to 17, but I thought I was sacrifice 400 RPM off of the top end for fuel mileage.
Also I was hoping to increase the boats power a little to try and get the 400rpm back.

I might go ahead and order a 14x17 4 blade, All the info I read on 4 blade props seems like they help with low end traction, help the boat get on a plane quicker, and the newer 4 blade props supposedly don't sacrifice much top end at all.
Right now I'm running a Turning Point 14x19 4 blade aluminum prop.

And what's WOT"3" stand for... I know what WOT stands for.. what's with the 3 at the end?


The "3" means look at the notes below the chart & note #3 is applicable to that particular information in the chart. Jim.

Ok, I'm offically dumb. lol! I guess I wasn't paying any attention to what I was looking at, I should have slowed down and read the complete chart.

 

[b.lee]

What rpm's were you getting with the old prop?

I didn't really check... I can always reinstall it and check. I know with the old prop I was getting 34 mph trimmed down and 38 mph or so trimmed up a little bit.
I gained maybe a mile per hour or 2 with the new prop swap for the first 2 weekends, but last weekend I was struggling to hit 35 mph when trimming up

 

[b.lee]

Another quick question... Can I run my boat in neutral, without any oil in the Outdrive?
I just want to set the timing for the cap/rotor, but I drained my outdrive oil last night and dont have the pump/adapter to refill it yet

 

[Bondo]

Can I run my boat in neutral, without any oil in the Outdrive?

Nope,.... Not a good idea, everything but the prop shaft turns with the crankshaft,....

 

[flipbro]

I had a 19 pitch 3 stainless rpms run 5000 wot plained very quick. My buddy had a 4 blade 20 pitch aluminum prop lying around so I put it on just to compare and it sucked my rpms dropped to 4700 and the boat didn't have the pull it had with ss . My guess is the aluminum blade flex at high rpms.On the brite side it did stay on plane at lower rpm. I believe 3 blade ss is better then 4 blade aluminum. Strictly an opinion lol

 

[b.lee]

Thanks Bondo

I had a 19 pitch 3 stainless rpms run 5000 wot plained very quick. My buddy had a 4 blade 20 pitch aluminum prop lying around so I put it on just to compare and it sucked my rpms dropped to 4700 and the boat didn't have the pull it had with ss . My guess is the aluminum blade flex at high rpms.On the brite side it did stay on plane at lower rpm. I believe 3 blade ss is better then 4 blade aluminum. Strictly an opinion lol

Thanks for the info
What kind of boat / engine are you mentioning above?

 

[flipbro]

20 foot wellcraft Elite 5.7 bored 40 over with a rv cam basic grind 420/444 produces really nice torque

 

[b.lee]

What carb do you have?

[h=3][/h] Mercruiser MCM 200/898 1389-8488