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87concord

87concord

Regular Contributor
"OK here it goes. I have a 19

"OK here it goes. I have a 1987 model boat with a 5.7 260hp mercruiser setup in it.I am going to pull the engine out this winter. I am building the replacement engine as we speak. I am using the block and heads out of a 1997 Chevrolet truck (vortec). I know that I will have to get a new intake to make the new heads work with the Qjet. I have friends that are saying truck engines dont work right in boats, is there any truth to this?? what differnces should I expect to find during the conversion?? I know i have to use marine starters, alternators, carbs, etc. anything else I should be aware of or is using the truck block and heads a bad idea? Any input will be appreciated"
 
"truck engine is ok. what mig

"truck engine is ok. what might not be ok is the flywheel. Have you givin thought to how your gonna bolt the coupler to it?

Exhaust you can get creative with.

Same series year wise engine, now thats the ticket."
 
"The truck engine will work, y

"The truck engine will work, you need to marinize it though. Use the flywheel off the old motor, my 1994 flywheel is now on my 2006 vortec and I bolted the old engine coupler back on there. Change out the freeze plugs to brass type. You will need a marine vortec intake manifold, I found a used aluminum brass lined one for $100 and reused my quadrajet. I reused all my old accessories (ignition, carb, water pump, p/s pump, starter, pullys, new belts though. I reused my exhaust (it was 1 year old). What are you going to do about the cam? Marine cams have a differant grind. I would look into an aftermarket marine specific cam. I have heard of street rodders installing marine cams in their cars for better torque. The truck cam might work ok if it's in a light boat. Repowering was the best thing I've done for my boat, it's a heavy 23' w/a. The 1994 was rated 235hp but it was tired and power was nowhere near original. The 2006 vortec is close to 300hp and it now performs as it should. It is quick to plane and cruise speed went from 24mph to 32mph because I am able to turn more prop."
 
"i am going to use a hot cam k

"i am going to use a hot cam kit from scoggin dickey, the cam i am going to get operates at well at about 4800 rpm"
 
Auto cams don't work well

Auto cams don't work well in Marine applications at all. Get one specific for boating applications. That's probably what your friends are refering to. Block and heads are the same. Probably want to stick with a four bolt main for strength and durability. All the rest is pure marine application.
 
"Ditto the remote filter and r

"Ditto the remote filter and remote oil drain hose.
Ditto Puget Sounder's suggestion re; the camshaft. The over-lap is important for low speed operation to avoid water reversion.
Also mark off your harmonic balancer while it is easily accessible.
The late engine will not be machined for a mechanical fuel pump.... not sure if that is an issue for you.

If you are using a "Closed Cooling" system, you can do just fine with a high grade automotive head gasket set.... only the Raw Water cooled engines actually require the marine set.

The truck engine will use the "dreaded" dished pistons to accommodate the small combustion chambers of the Vortec cylinder heads. Since you are custom building your own, you could go with a good Q/E (quench effect) reverse dome or low compression Quench style piston for a minimal cost difference!
If so, you will have a better performing marine engine, IMO.
(use the correct head set for the piston selection)

."
 
"Good choice using the dual pl

"Good choice using the dual plane intake manifold for a marine application.
The intake being automotive will pretty much dictate that you will be doing a Closed Cooling system (ethylene glycol).
If so, it will work.

If doing raw water cooling, the cross over should be bronze lined, such as found in the marine version aluminum intake.
(unlike metals will lend themselves to galvanic corrosion if raw water cooled)

The GM roller tip cam followers, so they say, will easily go 150K+ miles in auto use.
I'd think that if the roller diameter is suitable for the cam profile that you have selected, it should work. Check with your supplier!

."
 
"ricardo,

its a 20 ft plea

"ricardo,

its a 20 ft pleasure boat, draws water from the lake to cool, what intake do you suggest? also has a thru transom exhaust sysem, is the cam i suggested suitable or no?"
 
"David, re; the cam:
If you

"David, re; the cam:
If your Thru Hull exhaust has adequate back flow prevention flappers, and is high enough above the water line, and you can be sure that cooling water will not undergo reversion, then do as you wish.
I'd personally not chance it.

Re; Fresh Water.
There are a few common misnomers as to what "Fresh Water" means when it comes to engine cooling.
Some may call river or lake water, "fresh water"!
Another misnomer is that the ethylene glycol closed system is sometimes referred to as FWC!

To me, we've got one or the other:
**A "closed cooling" system using E/G (heat exchanger and ethylene glycol)
**An "open" or "raw water" system using the lake/river/sea water directly into the engine for cooling.
Which do you have?????

If an "open" or "raw water" system, then that intake manifold will eventually give you trouble..... even in lake or river water.

Rick, re-using roller cam follows (if correct for the cam profile) is not an issue. In fact, resuing an entire roller cam and followers is not an issue (unless of course they are entirely worn out).
(perhaps you may be thinking of flat tappet style.)

."
 
"Ayuh,... The Intake posted w

"Ayuh,... The Intake posted will work just Fine,...
The Cam is another story...
LSA of 112° is at the upper limits of a Marine set up,...
The dur.@ .050 is alittle High, but possibly runable...
But,...
The Lift with 1.6 rockers is More than the vortec heads will take,...
The springs collaspe,+ bind at those #s,...
Without serious machine work on the heads, you have to stay Under .500..."
 
"Bondo, we disagree on the iss

"Bondo, we disagree on the issue of an automotive "aluminum" intake manifold for use on a Raw Water cooled marine engine. I've seen the damage, but also do not want to lock horns with you!
David..... your call on that!
(I'm a strong advocate of a closed cooling system for marine engines! This may be the perfect time to install one on your new, fresh, rust free engine!)

I do agree with Bondo re; not using high lift for marine use. I too would stay under .500" but for a few other reasons as well.
Also, there is no need for excessive spring pressure..... we are not running high RPM (or should not be) on a cruiser type hull! IMO!

David, learn what you can about the Q/E type pistons, detonation reduction and how this can affect ignition timing and the performance gained by going this route.
Keep your camshaft profile manageable.

."
 
"[b]"Bondo, we disagree on

""Bondo, we disagree on the issue of an automotive "aluminum" intake manifold for use on a Raw Water cooled marine engine."

Ayuh,... Actually, I'll concede the point,...
Only because We have No idea whether this'll be a Saltwater motor, or a Sweetwater motor...
I live on the last Sweetwater Sea, Lake Ontario,...
Aluminum is a Non-Issue here...
Manifolds,+ risers usually last 40 years or more, unless allowed to Freeze of course...
Motor blocks,+ heads last Forever, unless allowed to Freeze..."
 
"Bondo, even if operated in wh

"Bondo, even if operated in what you are calling "sweetwater", the dissimilar metals will create a galvanic reaction.
He may get by with it for a longer duration, but it will eventually take it's toll on the aluminum.
With the closed system, and a mixture of E/G and distilled h2o, it will survive!

."
 
"[b]"Bondo, even if operat

""Bondo, even if operated in what you are calling "sweetwater", the dissimilar metals will create a galvanic reaction."

Ayuh,... I'm not going to argue the point, because Technically, you're correct...
But,...
From the practical point,+ from years of experince,...
There's Nothing wrong with running aluminum parts on freshwater boats...

"I have also looked into another cam that is sold for marine application. follow this next link and the cam has part number 295-122363"

Ayuh,... That's Better, but still on the ragged edge of reality...
1 point I see in the link, it lists it with 1.7 rockers...
1.7s Won't fit in SBC valve covers... 1.6 is the Max...
Those are BBC rockers...
And,...
At 1500 to 5500rpms,...Your holeshot is gonna Suck..."
 
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