missing some power, and oil pressure

[-stig-]

hello people!

have been out boating some in these last days with my 3.0 rebuild merc. have checked and rechecked the timing, and the timing advance. looks just fine. the compression is about 140-145psi on all cylinders (just overhauled, not run in yet).
but i think i'm missing some power, the prop is way to small, but it stops at 4600rpm, and according to some prop calculators im just using 60-70hp..
the previous owner ran the engine at 5500rpm, so i jut wonder what is wrong?
have checked the rpm with a shop tack to..
can the valves be a little loose? so the opening time is too short for more revs?

have ordered a new propell, because i dont want to run it that high, but if i'm missing half my power that is going to be a sad story.

and, i hae a strange oilpressure... i'm pretty used to car engines, but im new to these mercruisers, but on these engine i get 45psi, and it stays there, whatever rpm. bougth a new gauge and installed, same story there. any clues?

to last, it cant hold the rpms on the muffs, i can set it at 1500rpm, and it just falls slowly until the engine dies... carb adjustment?

thanks, and regards!

 

[dingdongs]

Re: missing some power, and oil pressure

your 4600 revs are correct for the engine.prop pitch is more important for what u want to achieve from your boat.these engines revving to the last owners figures is why it failed.a gps chartplotter or another boater will prove top speed if thats what your after but your engine seems ok.

 

[Rocky_Road]

Re: missing some power, and oil pressure

and, i hae a strange oilpressure... i'm pretty used to car engines, but im new to these mercruisers, but on these engine i get 45psi, and it stays there, whatever rpm. bougth a new gauge and installed, same story there. any clues?

thanks, and regards!

My 3.0L has only about 65 hours on it, and the oil pressure has always stayed right around the 40-45 range regardless of the engine speed. I don't think that you have any problems there....

As for the WOT rpm's...my 3.0L is red lined at 4800. I'm propped to go slightly higher, but I keep an eye on the tach. The 5500 that you mentioned would hand grenade mine!

Happy boating!

 

[Bondo]

Re: missing some power, and oil pressure

to last, it cant hold the rpms on the muffs, i can set it at 1500rpm, and it just falls slowly until the engine dies... carb adjustment?

Ayuh,... definitely sounds like a fuel delivery issue... Maybe also why it's down on power...

 

[-stig-]

Re: missing some power, and oil pressure

nothing is changed since the previous owners, just a new block, so i just cant understand why i cant get more than 4600 when they got 5500. i wount drive it that high, i know thats the reason that last engine failed, but it seems like its down on power. i'm going up on the pitch, it should do 42-43knots at 5500, now its doing 32 at 4600. all gps figures. its a 19p, i probably need a 23p.

like bondo says, probably a fuel issue. the stange thing is out at the lake at wot its nice and stable. so i cant figure out what it is.

good that others too got the same oil pressure, thats a rock from my head

and offcourse, all ignition parts are new, except the coil.

 

[Bondo]

Re: missing some power, and oil pressure

i'm going up on the pitch, it should do 42-43knots at 5500, now its doing 32 at 4600. all gps figures. its a 19p, i probably need a 23p.

Ayuh,... edit.misread the post,+ had it backwards...

 

[-stig-]

Re: missing some power, and oil pressure

so the best way is to solve the problem first, then change?

i was thinking that it did'nt like rpms over 4600 anyway, so i would just change at once...

 

[-stig-]

Re: missing some power, and oil pressure

i tried to adjust the valves again today, with no luck.

if i follow the manual i dont get any compression, so i have to back of the adjustment nut to just so i cant turn the push rod, then i get compression.

is my hyd lifters stuck? can that make a difference on the power?

had it going on the muffs again today, got it to run pretty smooth at idle, and it seems fine.

if i got the timing wrong on crank/cam, can that make my problems?
the markings was bad,but i think i got it right.

 

[-stig-]

Re: missing some power, and oil pressure

hello guys!

bumping this one!

was out on the water just now, and are still a bit confuced.

i have installed new lifters, and got things going ok, but still missing som power i think?

have changed the prop, now got a ss 14"x21 and got the rpm's a bit down, today i maxed at 45mph (gps) at 4600-4700 rpm. still, the boat is tiny and should'nt it go a bit faster?

tried to adjust ignition timing today, but i noticed no change even if i put it on 6degree or 12degree btdc.... isnt that strange? the idle change, but no change in the top..

stig

 

[Bondo]

Re: missing some power, and oil pressure

today i maxed at 45mph (gps) at 4600-4700 rpm. still, the boat is tiny and should'nt it go a bit faster?

Ayuh,... It might be a tiny boat, but the 3.0l is a TINY motor...
Those #s sound about Right...

 

[Don S]

Re: missing some power, and oil pressure

You have yet to mention anything about make (Mercruiser/OMC/Volvo), or year or what type ignition you have or size of boat or anything.

 

[JustJason]

Re: missing some power, and oil pressure

have changed the prop, now got a ss 14"x21 and got the rpm's a bit down, today i maxed at 45mph (gps) at 4600-4700 rpm. still, the boat is tiny and should'nt it go a bit faster?

Nope, thats exactly where you want to be. Your actually a tad high on the rpm side of things. I don't know why you thing your down on power. 3.0s accelerate fairly good, but you don't get that "seat being pushed into your back" holeshot that you would get with a 350 or a big 2 stroke outboard.

 

[-stig-]

Re: missing some power, and oil pressure

i'll try to answear as good as i can!

the boat is a Shakeapeare Shadow 15.9ft, about 1500lbs

the engine is newly overhauled 1986 modell, aprox 8hours runingtime, about 130psi on all cylinders when i measured on hot engine yesterday.
its installed a thunder something magnetic ignition on the engine. everything on the ignition side is new, exept the magnetic igniter.

it idles better now, pretty rough on cold engine, better when hot, but still have to adjust it around 900rpm, under that it buckles and dies after a while.

its a good idea about the carb, i should go over it, its the only piece on the engine i havent had my fingers on!

it runs good, but i i still think its kind of strange that it had more speed before, with the engine that went to pieces. but i guess 5mph isnt that much, if i get the engine to idle good i'll guess ill be happy!

thanks to everyone for good help!

regards

 

[Don S]

Re: missing some power, and oil pressure

Is this a Mercruiser or OMC?
Can you post a picture of your distributor, because, if you have a Mercruiser, they never used a Thunderbolt ignition systme on the 4 cylinder engines, but they did use the DDIS digital ign. sys.

 

[-stig-]

Re: missing some power, and oil pressure

its a mercruiser.

its a old style distributor, but with a magnetic pointer instead for the old point breaker. sorry if i did'nt make that clear, I'm norwegian, so i'm not used to make my self understandable in english