I need some help here guys. I'm having problems with my motor going into engine protection mode. Let me give you a little history.

When I bought the boat it had a 21" aluminum prop. I could not get over 4000 RPM or over 40mph. It took forever to get on plane.

I bought a 17" 4 blade SS Power Tech prop. Great holeshot and about 47mph at 4400 RPM. Great! At 4400 RPM the alarm would go off and the engine would drop down to 2000 RPM.

 My engine owners manual says WOT is 5000 RPM but when I go to Volvo and run my serial number (4012150295) it tells me 4400.

Swapped out the prop for a 19" 4 blade and now I'm running about 4000 RPM and 43mph. The 17" seems to be a better fit but I think I'm hitting the rev limiter.

Now for the interesting part. If I'm running at WOT, or close to it, when I back off the throttle to come off plane, the alarm goes off.

So I have two questions.

1. What should my WOT be? Even when I go to the Volvo site one document says 4400 and another says 5000. My Repair manual also says 5000. But the alarm seems to go off at 4400. So which is it???

2. What could be making the alarm go off when I'm backing off the throttle? I'm wondering if there is something else going on that is setting off the alarm at 4400 RPM.

Any ideas?

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Chris & Bonnie Hick
"School Boy Heart"
2005 240 EX

Your RPM range will be on the plastic cover on top of the engine, it should be 4800-5000 RPM.

 You will NOT get an alarm for an over rev, it will just start cutting out when you hit the rev limiter, so the prop is not your problem...I would stick the 17 back on there.  My rev limiter on my Volvo kicks in about 5100 RPM.  Have you watched your oil pressure and temperature?  If I was a betting man, I would bet that either the oil pressure sending unit or the temp sending unit is giving a faulty reading and triggering limp mode.  You have a 2005 I see...did you get the extended warranty?  This should be covered.

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Steve Kroesen
Apollo Beach, FL
Kroes Nest

Yeah, I was kind of thinking there is something other than the rev limiter going on. All gauges look normal when it happens. I was going to disconnect the temperature sensors from the risers and the water pump and see if that changes anything. From what I have read those sensors are separate from the sensor that reads for the gauge.

It's just odd that it happens so consitantly at 4400 rpm. If it was a bad sensor I would expect it to be more random. I may have to take it in to a mechanic to have the ECM read for faults.

I bought from a private owner, so no warranty.

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Chris & Bonnie Hick
"School Boy Heart"
2005 240 EX

Since I was over cheering Ryan on replacing an exhaust manifold today and seeing his after only 2 years makes me wonder if you have a riser clogging up...they do have a temp sensor in the back of them.  Might be possible since you purchased it used and don't know the true history of how it was flushed after use.

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Steve Kroesen
Apollo Beach, FL
Kroes Nest

Hmmmm. How would I know if one was clogged? Would I have to remove it? How difficult was the installation and how much did it cost?

 Hope you guys had fun at Beer Can today. Wish I was there.

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Chris & Bonnie Hick
"School Boy Heart"
2005 240 EX

Only real way to tell is by pulling a riser and have a look.  Don't do a Ryan and break your bolts off though!  Spray with some penetrating oil first and hit it with an impact wrench if you have one.  Other than that...overheating.  Cost...he paid the "convenience fee" as he called it so he could pick it up local, but you can get a full set of manifolds and risers for $400 and change here.

 

http://www.ebasicpower.com/exhaust/volex.php

 

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Steve Kroesen
Apollo Beach, FL
Kroes Nest