1989 Evinrude 150XP RPM's

Jace817boater · #1 January 30th, 2007, 05:25 PM

First a little history: I have recently aquired a 1994 17'4" Cajun Fish 'n Ski with a 1989 Evinrude 150XP (E89STLCEM) on the back. The boat sat for a while so I have changed out the water pump, thermostats, plugs, inline fuel filter, and rebuit the carbs on the engine.

The motor starts great, runs smooth, EXTREMELY quick to plane, and has tons of low end power. My problems is that the motor will not put out over 4200 RPM's. I asked the previous owner about this wondering if it was possible propped wrong, and he said no way in fact he thought it was a little under propped if there was a light load.

This lead me to believe that there is a fuel restriction. First place I looked was the fuel bulb and it was the larger size 3/8". Then I noticed that once the fuel line connects to the motor, on the inside the line is 5/16" with a 5/16" in line filter. Is this normal? Any ideas to the problem and what to troubleshoot?

Thanks in advance.

Dhadley · #2 January 30th, 2007, 06:12 PM

Let's look at the basics. If the motor really is only turning 4200 the hole shot would suck. On the other hand, maybe it does and it'll scare you when you get it right. LOL!

What pitch is the prop? What's the actual speed at wide open? If we know those things we can narrow it down a bit by figuring the slip %. We may have a faulty tach. Make sure it's an OMC or BRP tach and set on position 6.

ezeke · #3 January 30th, 2007, 06:18 PM

If you put a test prop on the motor and run it up you will be able to tell. You have not said what propeller is on it now.

My guess is that it is over propped. In any event you should be able to get to around 5800.

emdsapmgr · #4 January 30th, 2007, 06:29 PM

Usually, the 3/8 line runs up to the engine, then reduces to the 5/16 at the connector inside the cowl. If you are concerned about fuel delivery, replace the fuel connector on the lower cowl with the higher flow 393679, and run the hose direct to it. You are right to be concerned about the engine rpm's-they are too low, even below the factory recommended normal operating range. Should be closer to 5500 at full throttle, trimmed out. The engine is lugging at 4200. Any possibility that the tach may be off? Let us know what type and what pitch prop you are using.

Jace817boater · #5 January 30th, 2007, 09:55 PM

Thanks for all of the replies.

Excuse my ignorance, but I do not know the pitch of the prop nor how to find it. Is it engraved on it somewhere? I have my doubts to it being propped wrong because the holeshot being in the 3-4 second range and it being able to yank a tuber around without a hesitation.

At 4200 RMP it is running in the 48-53 MPH range via GPS under most conditions. The previous owner claims to have done upper 60's at 5500 RMP

I have not been on that many boats but it doesn't "sound" like a engine turning max RMP. I will check the tach as dhadley suggested for position 6.

emdsapmgr · #6 January 30th, 2007, 10:48 PM

The prop size information is located on the prop end, just behind the nut on the propshaft. Would read something like: 14 X 19 and then the part number.. Did you ever have the prop off? It may be time for a compression test and a spark test to baseline your engine's condition. Did you sync and link after the carbs were off? Are the throttle plates wide open when at full throttle?

Jace817boater · #7 January 31st, 2007, 12:33 AM

emdsapmgr, thanks for the prop info. I have never had the prop off. I will try to get a hold of a prop wrench and see what I've got.

I checked that all six of the butterfly valves were in unison and they were as well as being wide open at WOT.

Time to invest in a compression tester as well!

Thanks you guys for giving me some ideas to check out. I will report back with the findings.