Fully Involved
New Member
I have twin 4.3 mercruisers that idle smoothly, but at full throttle the port engine builds 2000 more rpm's. This just started and I am thinking that maybe it is time for a tune up. Any thoughts or suggestions?
RPM issues with twin engines
- Thread starter Fully Involved
- Start date
There is a about a 130 rpm difference with mine at full throttle. I plan to have the pitch reduced by 1/2 inch on the slower side to compensate for this when the boat is pulled for the winter. However, in your case something else is going on. Can you get full rpms out of the offending engine when the shifter is in neutral? If not, that's a pretty strong indication something is wrong with the engine and perhaps a tuneup might fix it.
Bucit
New Member
- Mar 12, 2010
- 3,144
- Boat Info
- 2005 280 Sundancer
2004 SPD-104 Achilles w/ 8hp Yamaha
- Engines
- Twin 4.3 MPI's with Alpha drives.
I believe all twin (counter rotating) engines will have slightly different RPM's. The port engine which is running in reverse will be slower but not 2000 rpm's slower.
Sundancer
Well-Known Member
- Jul 20, 2005
- 2,909
- Boat Info
- 34 year old CLASSIC 300 DA, towed almost anywhere behind the Duramax Dually Crew Cab.
- Engines
- 16 cyl, 700 cu. in./Alpha I's
Let's back up a little bit. When you say 2,000 rpms is this based on what the tach is telling you or do you hear the engine revving and validate with the tach? It could just be a spun prop hub or it could be something worse. When was the boat tuned up last? Is this something that started suddenly? I'm also guessing he has Alpha I's that aren't counter rotating, but who knows what was installed!
rcknecht
Well-Known Member
Sounds like you need to tap your finger on your guage... The ground wire probably need to be cleaned on your tac...
