articfriends

iTrader: (1)

Andy,on a bravo it should make no difference as the upper and lower thrust bearings on the gears are identical. Before he switched sides one drive was running on the upper thrust bearing,after switching the opposite side was running on the upper,Years ago there were some small blocks in boats that were lefthand rotation but that is a thing of the past,Smitty

tm29

OK I will try props first then, yes the boat has been doing it since ive had it. the only thing that has thrown me off about the props is that when i switch it straigtens out the problem. I figured if i switched then the port side would have been lower rpms and vice versa.

tm29

here is the exact rpms
when props are turned out starboard side is at 4500 rpm's and port side 5100

when props are turned in both are at 4800 rpm's and they sound in sync

one is a quicksilver mirage23p and the other is a quicksilver non-mirage
and thanks again for any help at all

Payton

I had a similar problem, when I discovered I had a 25p Mirage and a 25pMirage Plus. I was 400 rpms dif at WOT. Maybe when you reverse the props it evens back out because your making your hull act different and the one prop is slipping a little more to make it seem right. I would take the props to a prop shop and let them check to see if there is a diffence.
If there is a diffence between a Quicksilver and a Mirage, then I bet that is your trouble.

throttleup

The easiest thing to do is to try another set of props or have your props checked out. After the props are matched then go from there. You may have several problems going on but start with the easiest one and then on to the next one.
Even if they are the same props it sounds like one was replaced for whatever reason. If the old prop has been worked or reconditioned it may not run the same as the newer prop.

Matt

tm29

thanks alot for all the info, I will check into getting a set of props to try out

JaayTeee

You need to have the same type of prop on both drives.

You say 7.4 lx mpi ( the old 330's with port injection)
The rev limiters on those are set at 4700 rpm,
and one tach is saying 5100 ?

So....... the tach's don't appear to be accurate.

You need to check rpm's against a hand held tach.

Once you have a "matched" set (same model/pitch) of
props, and you can verify the true rpm, you have a
baseline to work with.

jt

tm29

thanks I will check the tachs. But it does show 5100 on the one engine when maxed trim. But I can here the engines are not in sync at all unless I turn the props inward

tm29

Do you think the owner could have changed the rev limiter by chance, Not sure if possible on these engines. Was just curious

JaayTeee

On MPI engines, the rev limiter is in the ECM.

It's possible they could have been "modified",
or maybe swapped for ECM's out of a 454 mag MPI ???

I think the ECM's are labeled, though.

jt