Mercruiser 5.7 won’t make power

[Oldpos]

I wouldn't be choosing a Cam, because of how it makes the Engine Sound. What sounds great in an Auto Engine, isn't the best for a Marine Engine.
Given the Same Duration and Lift, the Roller Cam, has the potential to make better Torque and HP than a Flat Tappet Cam. And as I said earlier, you don't have to worry about the lack of additives in Modern Oils needed to keep wear on the Cam low

No break in oil needed?

Can or would you use used roller lifters? I found the original lifters to this block that all look good. I kept all the original retainers lifters and pushrods

 

[Scott06]

No break in oil needed?

Can or would you use used roller lifters? I found the original lifters to this block that all look good. I kept all the original retainers lifters and pushrods

If cam lifters look good use them no break in on roller lifters

Flat tappet cam u need zinc zddp added or high zinc oil like driven or Lucas hot rod oil made for flat tappet cam

 

[Oldpos]

I went and bought this cam today, any thoughts or experience good or bad, Chevy ramjet cam

 

[Scott Danforth]

Unless you abandon wet exhaust and run jet boat headers, that cam has too much duration.

270 degrees is the max duration for wet exhaust

 

[Scott06]

Unless you abandon wet exhaust and run jet boat headers, that cam has too much duration.

270 degrees is the max duration for wet exhaust

Thought lift above .420 was too much for stock vortec head as well.

 

[itsathepete]

Unless you abandon wet exhaust and run jet boat headers, that cam has too much duration.

270 degrees is the max duration for wet exhaust

I have that exact cam in my vortec 350 and it is a very common cam for marine engines. Works just fine with wet exhaust. Zero reversion. Valve overlap is the issue with marine cams not just duration or lobe separation angle. I think you will be happy it is designed for low end torque with max HP at 4400

 

[Scott Danforth]

I have that exact cam in my vortec 350 and it is a very common cam for marine engines. Works just fine with wet exhaust. Zero reversion. Valve overlap is the issue with marine cams not just duration or lobe separation angle. I think you will be happy it is designed for low end torque with max HP at 4400

Do the calcs, this cam has too much overlap to be used as a marine cam.

It's a hotrod cam

 

[itsathepete]

Do the calcs, this cam has too much overlap to be used as a marine cam.

It's a hotrod cam

I wouldn't consider it a hotrod cam by any stretch. It is designed for torque and midrange. It is commonly used by marine engine builders as a stock cam. Many people have pulled it out of marine engines, including myself.

 

[itsathepete]

Thought lift above .420 was too much for stock vortec head as well.

It is at about the max lift you can run without modifying the heads. Not to say there absolutely won't be a problem, but many people run it on stock heads. Works great for me

 

[Scott Danforth]

Stock GM marine cam specs


202 duration intake
214 duration exhaust
395" lift intake
404" lift exhaust
112 lobe separation

 

[Oldpos]

Thought lift above .420 was too much for stock vortec head as well.

The springs I had installed take a lift of .490 and the last cam had a lift of .470. Duration I’m not as certain about

 

[Scott Danforth]

the cam I would suggest is the one that came in the suburban motor

however if you want to buy one, look at this one:

Xtreme Marine 212/218 Hydraulic Roller Cam for OE Roller SBC

Xtreme Marine 212/218 Hydraulic Roller Cam for OE Roller SBC

www.compcams.com

lobe separation make sure that there is no reversion. profile of cam is a short base circle with high ramp rate.

the XM270HR is the next cam up, however you need more torque down low and the XM270HR has some reversion issues at idle, and you are in a pontoon where you will be idling along often

Here is the overlap on the ramjet cam - 19 degrees total overlap which means that if you idle, you have reversion.

Here is the Comp Cams XM270HR with 3 degrees of overlap. this cam does have some reversion at idle and is recommended for jetboats

 

[itsathepete]

I was having trouble with that cam calculator web site last night. Kept getting a message saying it was down for maintenance. But I'm really confused. Maybe I'm not thinking correctly or reading things wrong, but the numbers indicate to me that the 395 cam with less duration even with the LSA of 109 gives less overlap (-17 degrees) than the XM264HR (-9 degrees) and definitely less than the XM270HR (-3 degrees). These numbers are using .050" lift and I understand that by definition, valve overlap is calculated using advertised duration and not .050" duration, which would put the 395 cam at 80 degrees overlap, the XM264HR at 43 degrees, and the XM270HR at 49 degrees. 80 degrees definitely sounds like a lot but that's due to the advertised duration of the cam of 288/308 which on the surface appears to be more of a high rpm racing/hotrod style cam, but it's not. With .050" duration of 196/206 It's a mild, low-end and midrange torque cam with a smooth idle. Perhaps the way GM measures or calculates their advertised duration is different than other manufacturers but I do know that many people, including myself, use this cam in marine applications with wet exhaust and don't appear to be having any problems.

 

[Oldpos]

Ok because y’all helped so much I will show you my ultimate red neck engineering. I don’t have a tree to hoist my motor out so this is how I have to do it.

 

[itsathepete]

Brother you are doing just fine. I had to use a tree the first time I did it. Now I have an atv winch on a steel beam across several trusses in my garage. My boat is low enough to get the engine out even with an 8 foot ceiling but I'm guessing your pontoon won't fit. As long as your hoist is secured you are good to go.

 

[Scott Danforth]

I made an a-frame from 2x10's, 2x6's and 4x4's. then when I was done, I used the lumber to make a mezzanine on the rented storage unit.

using the engine hoist in the truck works. just be careful the cargo tie downs do not come loose. they are only welded in the sheet metal.

 

[Oldpos]

I made an a-frame from 2x10's, 2x6's and 4x4's. then when I was done, I used the lumber to make a mezzanine on the rented storage unit.

using the engine hoist in the truck works. just be careful the cargo tie downs do not come loose. they are only welded in the sheet metal.

I found the real problem today. I had to pull the motor to fix it and the flattened cam anyhow.

I found the timing chain did line up as needed but the hormonic balancer mark was about an inch and a half off and the nbr 1 piston was a half inch below the deck of the block before tdc. I had major issues, timing of cam off, flattened cam. New cam went in beautifully and everything lined up as it should.

 

[itsathepete]

I found the real problem today. I had to pull the motor to fix it and the flattened cam anyhow.

I found the timing chain did line up as needed but the hormonic balancer mark was about an inch and a half off and the nbr 1 piston was a half inch below the deck of the block before tdc. I had major issues, timing of cam off, flattened cam. New cam went in beautifully and everything lined up as it should.

Well you sure work fast. Can't wait to hear how it all works out

 

[Oldpos]

I got it back in the water today finally, sounded so sweet with the 4 barrel open. I believe I have it all fixed except the fuel issue. When pulling power it skips a bit like a back fire except it’s the engine stalling for fuel I believe. As someone pointed out my pump is before the water separator so I need to fix that and I ordered a second electric pump to put by the tank. I got it up to 4200 rpm before I backed off because the fuel issue.

Thanks again to everyone who suggested something, this was not a single issue , it was a few things and all your suggestions really helped!

 

[itsathepete]

Great to hear. What prop did you go with and what speed were you able to attain?