2000 380 ac with 3126 cats, speed/ rpm and consumption questions

[sea dawg]

What hp are the motors and do you know prop size

Hello twyant,

thanks for the question and help... the engines are 350hp but unsure of the prop size.... i will try to dig that up...

the more i think about it, the more i am thinking that i may have the wrong prop size and/or pitch...

i went out this weekend and tested with a photo tachometer and found the following:

At idle, both engines gave out over 3000rpm,

in gear, the story changes:

Both at full throttle
port was 2340 rpm, stbrd: 2540- speed 19.3 /21 (gps)
this had the sync off in favor of stbrd so when sync'ed,
aka, port full throttle and stbrd adjusted to sync =
port 2239 stbrd: 2242

@ when the stbrd shows 2500 and sync'd-speed 10.8/12 gps)
port: 1790 strbd: 1800

when stbrd @ 1600 rpm sync'ed speed 8.5/9.1( gps)
port 1105 and stbrd :1170

i checked the trottle cables and they are adjusted to the max setting. I cannot get anymore rpm from the port or strbd..

even at both OT, the best i get is port :2327 2500 stbd, a full 300 rpm lower than manufacturer settings.

and when sync'ed, the best i get is 2200 ish... 600 lower. obviously, even though a lower rpm, i am assuming that i will be burning more fuel than i should be... obviously, the engines are working harder than they should be

props pitch off?? I can find out what pitch i have. I went under the boat and tried to have a look on the prop and could not locate any sizing....

Another issue i discovered over the weekend is that my grey water pump on port engine is leaking like a siv.... is it a matter of replacing a gasket or the whole pump...? it was hard to isolate where the leak was stemming from!!!

Thank you to everyone for the feedback and guidance.... and patience with this newbie owner...

:smt101

 

[twyant]

First if you syn'd the motors it does not go Thur the tachometers the motors will be the same rpm no mater what the tachometers reads
#2 Check The Engine size Sea Ray shows they did not put 3126 in this model it says it was 3116 350 hp
#3 Props should be 24x25x1.75 trans should be ZF 220A 2.0:1
Engines should turn 3100 + or -rpm wot out of gear it has a tag on top of the motor what they where set new , in gear at least should turn around 2750 rpm
Sea Ray shows this Boat wt is 2400 lb dry wt
Allot of things don't sound right with all this
I have The 420AC with the 3116 350hp I run @ 2400 rpm 23-24 mph wot is 2750 rpm 29-30 mph and is 27000# dry wt I did a lot of prop work done but only gained 2 mph wot
I would definitely look at the props first and change the tachometers you need them to be correct.
sounds like you port motor is pulling the starboard down I would look at that prop for damage first
Keep us posted

 

[sea dawg]

First if you syn'd the motors it does not go Thur the tachometers the motors will be the same rpm no mater what the tachometers reads
#2 Check The Engine size Sea Ray shows they did not put 3126 in this model it says it was 3116 350 hp
#3 Props should be 24x25x1.75 trans should be ZF 220A 2.0:1
Engines should turn 3100 + or -rpm wot out of gear it has a tag on top of the motor what they where set new , in gear at least should turn around 2750 rpm
Sea Ray shows this Boat wt is 2400 lb dry wt
Allot of things don't sound right with all this
I have The 420AC with the 3116 350hp I run @ 2400 rpm 23-24 mph wot is 2750 rpm 29-30 mph and is 27000# dry wt I did a lot of prop work done but only gained 2 mph wot
I would definitely look at the props first and change the tachometers you need them to be correct.
sounds like you port motor is pulling the starboard down I would look at that prop for damage first
Keep us posted

Thanks again, really appreciate your guidance and documents you sent over.


I double checked the survey and Cat' s emails ( who checked the ser #'s) and it is indeed the 3126...hummmm!! :huh:

I will keep going down the check list that seanile sent over... re possible fuel supply issues.... and of course, replace the tachs... the prop looks ok but it may be best to get it on the bench and have it looked at... maybe change the pitch... any suggestions of what to try changing the pitch to?

are they relatively easy to take off? do i need any special tools? I was thinking of throwing my scuba gear on and taking them off rather than having the boat hauled out....do-able???

thanks again

m