Hitting the rev liniter at 4000 rpm

Took my boat in in to have it checked as I just bought it. Its a 2004 Caravelle with the 4.3 GXI. Was having a problem hitting the limiter at 5200 the boat was over reving. Put a new prop on ss 20 pitch 4 blade it helped. The shop called and said it was hitting the limiter at 4000 rpm. What would cause the motor to hit so early? Thanks

Question: Why are you throttling up high enough to get into the rev limiter?
Your OEM spec'd WOT RPM is a test RPM....... not an RPM to be sustained for any length of time.

If you are wanting to perform a WOT RPM test (to see if you're propped and/or geared correctly), try disconnecting the limiter during the test.
Re-connect it afterwards!


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RicardoMarine said:

Question: Why are you throttling up high enough to get into the rev limiter?
Your OEM spec'd WOT RPM is a test RPM....... not an RPM to be sustained for any length of time.

If you are wanting to perform a WOT RPM test (to see if you're propped and/or geared correctly), try disconnecting the limiter during the test.
Re-connect it afterwards!


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Click to expand...

Did the mechanic actually say "hit the rev limiter?" Rick suggests (correctly) to run a test with the limiter disconnected. If you do not know how to do this, try this test... With a fully warmed up engine, shift into neutral. Momentarily blip the throttle ( shift enable button set to throttle only!!!) and see if you can exceed 4000 RPM. If you can, then you are not hitting the "rev limiter"...if mechanic said you were ( or did he say you hit max RPMs?) , find another mechanic. A good and honest mechanic would know that the prop he just put on the boat was "too big" for the boat and would have told you so and ordered the correct one for you.

If the engine is operating properly ( good plugs, fuel, timing, compression, etc) then you are most likely "overpropped", i.e. the prop that you NOW have on the boat is "too big" for the engine boat combo. Usually this means that the pitch is too high...or the diameter, or the blade count.

The REV limiter is for "oops" situations. Find the normal REV range for you engine in the owner's manual. The prop on you boat should allow you to achieve a WOT (Wide open throttle) RPMs within this range. IFSO, you have the correct prop, and the correct RPMs for you to run your boat engine continuously is 80% of that value... 75% if you want even longer life. Boat engine life when run continuously at MAX RPMS is measured in the tens of hours. at 80%.... thousands. There are only two conditions that justify running @ WOT... momentary test to check that engine is in tune and has correct prop ( or the bottom is clean) and to get out of danger. The occasional "lets see how fast it will go" is OK, but never for more than a few mins. But then again... it's your money!

Some dealers/mechanics see new boat owners as a "trust fund".

The guy I bought it from was running a 17 pitch. When I took it for a test drive it was hitting hit. This is my first inboard boat so I had subject to mechanical inspection. The shop I took it to I have been dealing with for the last 4 years and helped me with my outboard. They did a pre inspection on the outboard for me and never charged me. So I do trust the shop. Don't like running at wot that is why I got the prop changed. They even let me try a hi-5 prop to see if I liked it. Didn't like it so they gave me a refund. Just wanted to know if anyone heard of this happening and what would be the fix. Thanks for your help and info

The rule of thumb for prop pitch vs RPM is a change of 150 to 200 RPM per inch of pitch, all other things being equal.. So you went from a 17 pitch prop to a 20 which should drop your RPMs by 600 RPMs. My personal experience with this is that this 200 RPM vs inch change usually only holds for about a 2 inch (typical increment in prop pitch between sizes) change. Beyond that , the non linear shape of the engine torques vs RPM curve shows itself and greater changes in RPM occur. Also, there may have been another reason that the original prop allowed the engine to hit the rev limit, most likely a slipping hub. If you still have access to the original prop, take it to a prop shop and have it checked out. While you are at it, ask them to check that prop's ACTUAL pitch and diameter. It is not uncommon for boat owners to have their prop pitch or diameter altered.

mxzretta said:

Just wanted to know if anyone heard of this happening and what would be the fix.

Click to expand...

The first "fix" is to stay out of Wide Open Throttle RPM, unless you want to shorten the life of your engine.

The next step would be to prop it correctly, so that you do not need to get near this RPM range.


Capt Bob is offering you some great advice. Take heed!



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The motor at wot is suppose to be between 4400-4800. The limiter is not suppose to kick in till 5000. So I'm trying to figure what would and why is it kicking in at 4000. The shop said my tach is reading right. It was doing this when it was hooked up to their dyno.

mxzretta said:

The motor at wot is suppose to be between 4400-4800.
That sounds correct.

The limiter is not suppose to kick in till 5000.
That also sounds about right.

So I'm trying to figure what would and why is it kicking in at 4000. The shop said my tach is reading right. It was doing this when it was hooked up to their dyno.
So.... you're reaching 4k RPM only while testing for WOT... is that correct?

If so, that answers my question as to why you are running near or above 4k RPM.

Click to expand...

Why not replace this component?
Or...... if you do not absolutely need the rev limiter, would you be able to disable it?


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When I had the boat on the water it did kick in at 5000. I know not to run it at wot but wanted to see if I was propped right. As for to disable not sure where to do this at and wouldn't want to. Think it is part of the ecm so wouldn't be able to.

Well... you have two issues and too many unknowns. Time to eliminate some unknowns. The simplest one to eliminate is the why did the engine rev to 5000. There are two possibilities... under propped or slipping hub... see my previous post.