Volvo Penta 7.4 GI WOT RPM

[alindquist]

(engine serial # 4110176452) I took my boat out yesterday and it seems it is finally running right again... I am however having one problem, at WOT I'm only getting about 4000 RPM's. On top of the motor it says it should be between 4200-4600. Any ideas? I was getting about 46mph on the GPS and I think if I can get it to turn 4500 - 4600 I'll be well into the 50's. Quick list of recent changes: oil change, fuel filter, impeller, plugs, wires, cap, rotor, risers, manifolds, and ignition coil. Also I did have it hooked up the computer and it showed no fault codes and it has 383 hours.
Aaron

 

[Bondo]

Re: Volvo Penta 7.4 GI WOT RPM

Ayuh,...

Right up in the Adults Only section,...
There's a topic down at the bottom called,...
What to look for when your motor won't make rpms, or something like that...

Have a Look There....

 

[Don S]

Re: Volvo Penta 7.4 GI WOT RPM

How long has it been sitting in the water?

 

[alindquist]

Re: Volvo Penta 7.4 GI WOT RPM

it sits on a trailer next to my house...

I'll take a look at that thread bond-o

 

[alindquist]

Re: Volvo Penta 7.4 GI WOT RPM

I took a look at the list and the only one that stood out was the oil level, I know there is a little too much in the engine, I'll guess I'll get that out and give it a try again next weekend. Any other ideas are more than welcome. Is there a way to change the timing curvers in the computer on that engine?

 

[Don S]

Re: Volvo Penta 7.4 GI WOT RPM

Is there a way to change the timing curvers in the computer on that engine?

Nope

Since I posted the list, I know you have not had a chance to test all the possibilities. You are ASSUMING everything is ok. Hate to tell you, but something is wrong, and a quick look at the timing with a timing light will either confirm or disproove the timing issue.

 

[JustJason]

Re: Volvo Penta 7.4 GI WOT RPM

The very first thing you should check is your boats tach against a known good shop tach.

 

[alindquist]

Re: Volvo Penta 7.4 GI WOT RPM

I dumped about a quart of oil out of the engine and got it to the level it should be at. I also checked the time and it is set at zero (is that right?). Ran the boat last night and I'm still only getting 4000 RPM's and about 46mph. I'm guessing next step would be to check the fuel pressure? How do I do that? Any other ideas?

 

[QC]

Re: Volvo Penta 7.4 GI WOT RPM

Do you have any history on this boat? You said "finally running right again". What did it use to do?

JustJason beat me to my first question on any WOT RPM thread . . .

Edit: I just read your profile and a 310 bhp 7.4 may not get a 232 much past 47, in fact that seems about right. If you have always had this boat and now it runs slower than before I would be concerned. If you have no old data, then this isharder to nail down. What altitude are you boating at? Have you ever changed the propset? Have you personally ever seen more RPM with this boat?

 

[alindquist]

Re: Volvo Penta 7.4 GI WOT RPM

I've had the boat for about 4 years. It has ran great ever since I bought it, at WOT I was getting about 4300 RPM's and the boat would run between 50-53 mph on the GPS. This spring I realized that my manifolds and risers were leaking. They have been replace along with everything else I said was replaced. Now I'm trying to figure out why I'm not turning the RPM's that I was last summer.

 

[QC]

Re: Volvo Penta 7.4 GI WOT RPM

Sorry, we were posting at the same time . . . Then you do have something to work from. I'd still check the tach. 53 GPS and 4300 RPM seems really good, but she should be able to do it again. Same load?

 

[alindquist]

Re: Volvo Penta 7.4 GI WOT RPM

Same load, I had 4 people and about 3/4 tank of gas last night. I will check the tach next time I out, I just need to track down a known good tach.