Papasmurf

Anyone here that has this engine ever changed the 4600 RPM rev limiter? There is a dealer in New Jersey that says they have, JJ Performance, but their website is no longer active.
Replaced my 900 hour 502s with a couple of these last summer, and love them. Boat was down for 2 weeks max doing the change over, Just plug and play. Rejet carbs and off they went.

Griff

You must have a TB V ignition. Change it to a TB IV which has no rev limiter or go with a DUI ignition system.

Baja Rooster

iTrader: (1)

Papasmurf

Yes, It has the Thunderbolt V system with knock control. That's a GM product, correct ? Cant find any info on internet on V System Module or where to buy them. What part number has the higher rev limiter.

Griff

First, No TB V's should have a 4600rpm rev limiter. The min would be 4750rpms for the 7.4's.

Exactly what engines did the ignitions come off of??

BUP

iTrader: (9)

Merc 540 reman 4 v carb -- max rpms is 4600 rpms and limits at 4700 -- T bolt V with knock control module and spark control module - ICM

The T bolt IV and T bolt V are the same exact distributors / caps and rotors and use the same exact ignition sensor under the cap & rotor

Timing for this app is 10 degrees BTDC
87 octane pump gas.

I have worked on 2 only but i do know about these fairly well..

Knot 4 Me

Must have a boom stick for a camshaft to have such a low RPM limit. RV cam! Were these things geared more towards heavy arse cruisers or something?

Papasmurf

Found the guys, they are Clauss Marine in New Jersey. They are getting me a V module with a 5200 limiter.

Here is what they have on their website about the Reman 540:

This engine is the biggest secret in Mercruiser's engine line up. It is rated at 440HP from Merc but what they don't mention is that itis rated at 4600 rpm. The reason they had to limit the horse power rating on this engine is because if they rated it at what it really makes it would fall into the Merc Racing line of engines. This would mean a different pricing level along with being restricted to Merc Racing dealers only, instead of being available to all Merc dealers. The engine does have a factory rev limiter set at 4600 rpm so if more power isn't necessary for you just leave it be. However to unlock the true potential of this engine we can supply you with the 5200 rpm ignition module which takes this engine OVER 500 horsepower. 520 horsepower to be exact and BIG torque. Add an aftermarket exhaust and pick up another 30 horses!!!!

We know this because we put one of these on our Superflow engine dyno. After building countless 540CID engines and knowing how easy it is to get 600hp out of one, (even with stock rectangular port heads, which is exactly what this motor has). We could not fathom this motor only making 440hp. We knew the compression is on the low side but it just did not add up. So when one of our customers ordered on we threw it on the dyno before installing it. That is when we realized it had a 4600rpm limiter. After one call to our Merc rep he let us know the deal and gave us the part number for the 5200rpm module. This motor is 100% complete!! A true plug and play with a warranty.

So if you want Merc Racing performance with out Merc Racing price along with a 1 year warranty (3 year Available) This is the engine for you!!!

All engines are shipped via freight truck. Please call us for an accurate shipping quote.

BUP

iTrader: (9)

This engine is under rated on the hp listed to begin with, it is 470 or 490 hp, forgot which one. It has 560 tq in stock form at 3600 rpms.. The valve train is nothing to write home about. It has stamped steel rockers and 800 cfm carb. The camshaft is a limited bump stick.

The t bolt module is nothing special it can be bought thru any Merc dealer across the world.

The pricing level retail is 20 K for this and mostly 21 K. I can look it up to be exact. It is under the reman side for Merc plus its a standard sized block. This is some of the reasons for Merc listing not persay under the racing side. Plus its cheaper to paint it all black for them as well and has a Carb,

with all this said no way changing the module ALONE is going to go from 440 hp to 520 hp I will call them out on this as PURE marketing of an 80 hp increase for a 400 dollar outdated module and ignition set up along with that installed cam, low buck valve train and heads ? apple to apples dyno testing just by changing the module. hmmmm

Papasmurf

I would be more interested in what the engine dynoed at 4600 when they tested. I agree, the engine is underrated for sure.I have a 1993 35 Lighting Non Step Hull and I believe the stock carbed 502s where making around 380 HP stock. Boat still had the 25P 3 Blade Mirage props that came on it from the factory. With 900 hours, they still turned 5200 and pushed the boat along around 68 to 69 mph.
With the new engines, I'm spinning 28P Bravos agaisnt the rev limiter at 4600. That gets me 72 all day, any day, with 4 people and full load of fuel. Im happy with that, but always looking for cheap HP. Gonna try some 30P Bravos this spring just to take the engines of the limiter. I figure to loose 3 or 400 RPM and the speed stay roughly the same.

Oh, and if you shop around, and give your local dealer a chance to "match" some pricing, you can get this motors for under 16K. Of course I bought 2 at a time.