Max rpm on a 1996 evenrude E150ELEDB

[tjspei]

Hi

I am trying to figure out what the max rpm is on a 1996 Evenrude 150hp E150ELEDB. My boat is a 1976 18ft and the engine is maxing out at 4200 rpm. I am not sure of the prop pitch but my boat jumps on plane REALLY fast it just wont go much past 4200rpm. I think my boat mechanic doesn't have the throttle cable set up correctly and it should have some more top end. Also that top RPM doesn't change much if its just me with a half tank on the boat or 2 guys and fishing gear with 2 coolers full of ice and a full tank of gas.

Thanks
Tim

[Bushwacker]

The first thing you should buy after getting any boat is a copy of the engines factory SERVICE MANUAL! Those old carb'd motors are basically very simple, so you can do a lot of your own maintenance, and the linkage adjustments are clearly illustrated in the manual. Most engines that are overpropped (too much pitch) are typically SLOW to get on plane, so you may be right that the motor isn't developing full power, for whatever reason. 4200 rpm is way too low for that motor. Just pull the air baffle off the front of the carbs and with the ignition off, advance the throttle to max and then look at the carb throttle plates to make sure they're wide open. If not, there is a knurled knob on the throttle cable under the cowling that is adjusted to put the throttle butterflies on the wide open stop. There is also an adjustment that determines where the throttle is when you hit full spark advance. On my old V-4, there was a mark on the throttle cam that lined up with a roller on the throttle linkage when the spark advance linkage hit it's stop. This is all described in the manual.

If the linkage is ok, the next step is check basic stuff like ignition timing and compression to make sure the motor is mechanically healthy with no bad rings or scored cylinders. If compression variation is within 10% on all cylinders, the next thing I'd check is to make sure you don't have a clogged high speed jet, as this can quickly kill a motor by leaning out a cylinder and overheating/scoring a piston and or cylinder wall! Easiest way to do this is have someone else run the boat at WOT with the cover and air baffle removed while you look down the carb barrels with a good flashlight. You should see a big spray of fuel in all 6 barrels. If one is spraying less fuel than the others, IMMEDIATELY come off plane and head back to the dock at idle speed! The low flowing carb will require a teardown, cleaning and rebuild. If one carb is full of gunk and varnish from old fuel, it's probably worth cleaning all of them and replacing all the fuel lines on the motor. I've seen old fuel lines with a film of varnish in them that can break loose and plug up a carb!

Your owners manual or the service manual will specify the WOT operating range, but typically the OPTIMUM rpm is right in the middle, so if it specifies a range of 5000-6000 rpm, you'd like to see 5500-5600 @ WOT with the max load you normally carry. Of course this assumes the tach is accurate, and many analog tachs are notoriously inaccurate even when new, so after making sure the engine is developing full power, have a dealer compare your tach reading with a known good tach to make sure it's accurate. Once you know the tach is ok, the next thing to check before changing props is to make sure engine mounting height is correct. When boat is up on plane, you should be able to clearly see the top of the anti ventilation plate above green water; this typically requires the AV plate to be about 1 inch or more above the bottom of boat.

A 150 is PLENTY of power for an 18, so unless the boat is full of waterlogged foam, I'd think you could spin at least a 17 or maybe a 19" prop.

[gofastsandman]

There is a bell curve in my manual. Makes full powah at 5k. Just over spin at that point.

[eggsuckindog]

Bush is correct though 5400-5600 is perfect - last time we had this the motor was only running on 5 cylinders = rifgr at 1000 RPM at the top. Check carbs first as that is easy

[gofastsandman]

Max rpm is 6100 on the rev limiter. Mine has a sweet spot @ 3700 and that is where I run her, unless being chased by a furry hat in the snot.

[tjspei]

Thank you for all of the replies. I will be going down the list checking your suggestions. Though I can only get it to max at 4200 I also find that I spend the majority of my time at 3700. Off of NJ where I run my boat its usually to rough to run any faster. I just want the extra power in case I ever need it.

Thanks again
Tim

[76Red18]

Check the throttle body advance roller. Not the roller for the timing advance on top of the motor but the roller on top of the starboard throttle body assembly. The rubber roller usually disintegrates every couple years and keeps the throttle plates from opening all the way causing about an 800 rpm loss. Theres a little o ring that keeps it on the shaft.

[Beaver]

As 76Red18 mentioned, it may be that your carb linkage is out of adjustment. You can check this really easily by removing the silencer from the outside of the carbs and with the motor not running push the throttle wide open. When you look inside the carbs are the plates open all the way and the same amount for each carb? If not you need to adjust the linkage. I think its called "syncing your carbs". I'm sure there are several youtube videos showing how to do it.

[eggsuckindog]

as I said thats first just because its easy, also a SHORT run with box off a look in there and see whats going on - the guy down here in Apollo Bch had a complete jet missing in the carb?? and it idled fine but when it got up just flooded everything

that equated to exactly 1000 rpm with the exact same engine

Max RPM or what the rev limiter is set at has absolutely nothing to with anything - it just needs to kinda close like 5400 so the motor doesn't lug down like driving around in 4th gear all day - 1000 is not right, something is amiss - its not prop either

also it needs to be de-carbed - google Dunks Method - it will not fix this issue just needs to be done on those OMC motors regularly