WOT on 4.3 merc

[20002760]

I have a regal 2760 year 2000 with 4.3L mercs, Alpha 1, 15.25" x 19P props. My WOT is only 4000 rpm and I should be seeing 4400-4800 rpm. GPS speed is 39mph and should be 45-49mph. Carbs are very clean. Plugs are new. Its a freshwater boat with a clean hull and zero corrosion. What am I missing? Could it be a timing issue? Please help!

 

[mkast]

Re: WOT on 4.3 merc

Look in the stickys.

 

[AZSenza]

Re: WOT on 4.3 merc

How is the performance up to 4000 rpm? is it sluggish? How new are the fuel filters?

 

[20002760]

Re: WOT on 4.3 merc

Just read "How to ask a question" so:

Engine Transom Drive
Port 0L606199 0L800764 0L717983
Starboard 0L606161 0L800779 0L717983

Fuel filters are about 8 months old.

 

[20002760]

Re: WOT on 4.3 merc

missed your other question. It doesn't seem sluggish and motors run smooth

 

[mrchev]

Re: WOT on 4.3 merc

have you had the boat awhile? did it use to reach that rpm? what prop pitch is on it?

 

[Robbabob]

Re: WOT on 4.3 merc

Assuming everything with the engines are "perfect", you need to pitch down with the props. I think that is why the questions about the newness of the boat to you. is there a new problem you've not shared or has it always been low on rpm?

Seems you can lose an inch in diameter and maybe 2" in pitch.

AGAIN. Is this boat new to you? Has the rpm been higher and now there's a problem? Both engines behave the same? I can help from a prop perspective... http://forums.iboats.com/showthread.php?t=287818

So many questions... ;-)

 

[nikogto]

Re: WOT on 4.3 merc

If it's not sluggish from a dead stop to 4000 rpm's, you may need to drop down to 17p props. That should get you into the 4400-4800 rpm range. If you were getting that rpm before with the props you have, then you have other issues

 

[20002760]

Re: WOT on 4.3 merc

I've had the boat for a year and I called regal with my HIN# and was told these are the original props. However I have communicated with others that have the same boat and some are running 14.25 x 21p while I have 15.25 x 19p. The GPS from the previous owner is on the boat and has much higher recorded speeds.

 

[20002760]

Re: WOT on 4.3 merc

Also the props are Mirage Plus. Both engines are behaving the same.

 

[PuddleJumper]

Re: WOT on 4.3 merc

Are trim tabs up and outdrives trimmed out at WOT? Has boat been moored on a lift vs in water.(water log or dirty bottom)

 

[20002760]

Re: WOT on 4.3 merc

tabs up and drives up. Boat has been trailered

 

[Tail_Gunner]

Re: WOT on 4.3 merc

ESSENTIAL DATA REQUIRED
When posting a question about propellers, you cannot get a reasonable answer unless you provide the following information in your post: Items 1-4 are essential for meaningful response to most questions.
1) Performance issue you are trying to correct.
2) Current prop manufacturer, model, aluminum or stainless as a minimum.
3) Current prop diameter and pitch (required).
4) Wide open throttle RPM and speed with an average load (very helpful)
5) Engine/drive make, model, year, and HP
6) Boat make model, year, length and weight


As much of that as you can .....Gearing speed and rpm are very important...The gearing is stamped on your outdrive....1.98...1.65

 

[20002760]

Re: WOT on 4.3 merc

1) Performance issue you are trying to correct. LOW WOT
2) Current prop manufacturer, model, aluminum or stainless as a minimum. MIRAGE PLUS, 48-13701 19P & 49-13700 19P, SS
3) Current prop diameter and pitch (required). 15.25 X 19P (ORIGINAL PROPS)
4) Wide open throttle RPM and speed with an average load (very helpful) 4000RPM 39MPH
5) Engine/drive make, model, year, and HP 4.3 MERC, ALPHA ONE GEN 2, YEAR 2000, 220HP
6) Boat make model, year, length and weight YR 2000 REGAL 2760, LOA 30'8", 8500LBS DRY

 

[Tail_Gunner]

Re: WOT on 4.3 merc

You have a lot of boat for a 4.3...Your gearing needs to be posted to get close

 

[Robbabob]

Re: WOT on 4.3 merc

The fact the boat has recored higher speeds and "others are running a 21P" prop, makes me think the engines are not running properly. Perhaps the weight has increased over 1000#. Again I state, you can reduce up to an inch in diameter and go with a 17P.

Check those engines for proper timing and compression before any prop change.

 

[Tail_Gunner]

Re: WOT on 4.3 merc

1) Performance issue you are trying to correct. LOW WOT
2) Current prop manufacturer, model, aluminum or stainless as a minimum. MIRAGE PLUS, 48-13701 19P & 49-13700 19P, SS
3) Current prop diameter and pitch (required). 15.25 X 19P (ORIGINAL PROPS)
4) Wide open throttle RPM and speed with an average load (very helpful) 4000RPM 39MPH
5) Engine/drive make, model, year, and HP 4.3 MERC, ALPHA ONE GEN 2, YEAR 2000, 220HP
6) Boat make model, year, length and weight YR 2000 REGAL 2760, LOA 30'8", 8500LBS DRY

19 pitch 4000rpm
17 pitch 4200
16 pitch 4400
15 pitch 4600
14 pitch 4800

That sounds right at a glance....27' 8500 lbs...4.3 220hp 14p prop....4 blade. A 19 pitch prop and a 20 foot 4000lb boat with a 4.3 is close to the edge im sure you have way to much prop

Loaded with fuel you probably 10k 100 gallon tank @ 8 lbs per
gallon is 800lbs

 

[20002760]

Re: WOT on 4.3 merc

I have twin motors. Compression is great

 

[20002760]

Re: WOT on 4.3 merc

How do I get this moved back to Mercruiser i/o thread? It is not looking like a prop problem.

 

[Don S]

Re: WOT on 4.3 merc

If and before this gets moved, did it ever run at the proper WOT rpm with those props? Normally (if ever) a mechanical problem will effect both engines as it has yours, and at the same time. Are the tach set properly for a V6? Are you trimming the drives properly?