305 to 350 build questions

gr8shot

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May 30, 2019
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Got a great buy on a 99 sea ray with a carbed vortec 305 that has a cracked block. Boat is like new for the age and I'm wanting to swap to a vortec 350 since the 305 needs to go to the scrap yard anyway.

The engine is bolted to an alpha one sterndrive unit which I've read doesn't like anything above 300hp. So I'm wanting to put together a 350 to stay at or under that 300hp mark, and get the most bang for the buck without breaking the bank. So I'm hoping to get some input from you guys. Here's my thoughts at the moment.

I'm planning to start with a vortec truck motor, which can usually be found for around $500 in good condition pretty regularly. First off I have mixed feelings about cracking open the motor just to swap to a SS head gasket when the motor will never see salt water. If totally necessary I will though.

Here's the rest of the questions though. Planning to stay carbed, and likely go to something like an edelbrock performer intake and the 1409 600cfm marine carb. I'm not opposed to swapping out the truck cam for a marine cam. But looking at specs, the marine cam actually has more lift and duration than the truck cam. With the alpha one being my limiting factor at around 300hp, I don't want to go too hot on the motor and just wind up toasting the sterndrive unit.

Basically I'm asking what would you guys recommend engine wise to perform well, not break the bank, and keep my outdrive alive? Are there good proven combinations at the ~280-300hp mark?
 

alldodge

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The 300hp Alpha limited is bases more on torque then hp, its just hp is easier to determine. My buddy has a 21 foot checkmate with a 383 and Alpha drive also using a 8 inch extension box, and has been using the boat for over 20 years. Was out last week and was hitting 70 mph. The point is if the boat is light, then there isn't as much concern with hp

What boat do you have?
 

Scott Danforth

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buy something like this http://centerstateengine.com/new-ma...-with-carburetor-replaces-years-1996-present/

drop in and go boating

As AD indicated, with an alpha, its the torque, and in many cases, the re-entry to the water after you launch the boat off a wave. plenty of 383 strokers in front of Alpha drives with much more than 300hp. make sure to run a rev-limiter

if your staying wet exhaust, you are limited to 270 degrees duration on your cam.

I will also echo the question, which SeaRay do you have?
 

gr8shot

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Sorry for not giving all of the info. It's a 1999 sea ray 190 signature. I believe dry weight is 3000lbs.
 

gr8shot

Seaman
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May 30, 2019
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buy something like this http://centerstateengine.com/new-ma...-with-carburetor-replaces-years-1996-present/

drop in and go boating

As AD indicated, with an alpha, its the torque, and in many cases, the re-entry to the water after you launch the boat off a wave. plenty of 383 strokers in front of Alpha drives with much more than 300hp. make sure to run a rev-limiter

if your staying wet exhaust, you are limited to 270 degrees duration on your cam.

I will also echo the question, which SeaRay do you have?

Not wanting to spend that kind of money though. Not afraid to do some of the work myself and get a motor up to speed to be a good performer. With as durable as these motors are, I feel pretty confident with a lower mile truck motor takeout.

Also good to know that it's not necessarily a hard limit as to what the alpha can take. The main lake we boat on is very small by most standards, so big waves and the boat coming out of the water isn't going to happen. And I don't see many all out top speed runs either. With our current boat (91 VIP 17'/3.0 alpha 1) we just like to pull the kids on a tube, put around, and the occasional higher speed blast across the lake. But even then, I just like to get on plane and cruise at a speed where the motor is comfortable, not running full tilt. So I don't need tons of power by any means. Just want the best bang for my buck when putting together a replacement engine.
 

Scott Danforth

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The 190 is a great boat. same as the 2002 I had (left over 2001 production, registered as 2002)

no problem with a low mileage truck motor (just make sure you add up all the costs directly and compare
buy a 5.7 vortec truck motor from a 1996-1999 truck (about $500). keep in mind the LS motors came out in truck starting in 1999
pull the long block apart
toss the steel core plugs, the steel head gaskets, and the steel water pump
install brass core plugs (about $11)
install marine head gaskets and new torque to yield bolts (about $170)
install a new marine water pump (about $75)
while at it, I would install a decent marine cam, like the XM264HR and a new timing set. this will require the valve seal bosses to be machined for clearance ($532 for the cam, lifters and timing set, $100 for the head work)
Install a new damper (about $50)

that is $1338 so far ($806 without the cam)

if you want to go 4-barrel, now is the time - (About $750 for intake and carb and spark arrestor)

that is $2088 so far

transfer the flywheel, knock sensors, and accessories over. (you will need to get the right knock module for a 5.7)
new exhaust gaskets to install your existing manifolds (about $25)

add misc., incidentals, etc. and you are at $2250 for installing a used truck motor with a new marine cam

where the new 5.7 vortec marine motor with an intake and carb and warranty is just a bit more.
 

Rick Stephens

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Scott is on the money.... but no way I would install an un-rebuilt pull, out of a truck. Disassembly, tanking, boring, new pistons rings bearings is so cheap, and long run, big payback. Use FelPro marine gaskets. No need ever on a sterndrive motor for a high volume or high pressure oil pump. Go through the heads, as Scott noted as well. I'm running a performa and a 1409 Edelbrock. Good setup, easy to calibrate.

Since this is new to you boat, go through the sterndrive and all the accessories. Know you will need to reprop with more horsies.
 

QBhoy

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The alpha will be just fine. As mentioned, it’s the torque that brings the question up. Even then. That’s only at risk if you are constantly opening the throttle up full from a stand still all the time.
I can’t think of many or any 5.7 carbs over 300 hp without serious work or even being stroked.

even the MPi 5.7 in maxing out at 300hp. The usual carb 5.7 originally had 250/260hp. There are vast numbers of these already fitted to alpha ones from the factory.
 

gr8shot

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I'm kind of in between what to do here. I only paid $1500 for the boat. Got a total steal, it's like brand new inside and out. I 100% plan to get it fixed and ready to be on the water this spring. But undecided as to whether we'll keep it or not long term. We'll either keep this boat and sell the 91 17' VIP. Or sell them both and upgrade to a pontoon.

With that degree of uncertainty, I don't want to dump thousands of dollars into the motor if we wind up selling it. But I don't want to skimp out and have to fix it twice either. I want it to be reliable and perform decent. But I don't need to set any speed records by any means. Looking to find that happy medium of not spending unnecessary money, but still a good degree of confidence that it'll be reliable and run as good or better than the stock 305.

I've got a motor bought as of now. 105k mile motor out of a 97 half ton chevy. Needs head gaskets. So here's my thoughts for right now (subject to change). Put in the marine SS head gaskets, leave the truck cam and valvetrain alone. Edelbrock performer intake and 1409 carb. Bolt on the manifolds and accessories from the 305 and get it ready to be in the water. I'll also check out the lower unit and change fluid while I'm working on it.

The other idea/question that popped into my head, can I use the stock marine cam out of the 305 in the 350? Will it be the same cam as would be in a marine 350? If so, I can pop for new lifters and put the cam from the 305 into it and get a few more free ponies.
 

alldodge

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If truck motor needs head gaskets, it may also need head work

can I use the stock marine cam out of the 305 in the 350? Will it be the same cam as would be in a marine 350?

The stock marine motor is normally just a truck motors with marine parts, but cam isn't one of them
 

Scott Danforth

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If truck motor needs head gaskets, it may also need head work



The stock marine motor is normally just a truck motors with marine parts, but cam isn't one of them

head gaskets for glycol duty in trucks are not stainless like they are for the marine world. hence the reason to change the head gaskets (or install a heat exchanger)
 

Scott Danforth

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I'm kind of in between what to do here. I only paid $1500 for the boat. Got a total steal, it's like brand new inside and out. I 100% plan to get it fixed and ready to be on the water this spring. But undecided as to whether we'll keep it or not long term. We'll either keep this boat and sell the 91 17' VIP. Or sell them both and upgrade to a pontoon.

With that degree of uncertainty, I don't want to dump thousands of dollars into the motor if we wind up selling it. But I don't want to skimp out and have to fix it twice either. I want it to be reliable and perform decent. But I don't need to set any speed records by any means. Looking to find that happy medium of not spending unnecessary money, but still a good degree of confidence that it'll be reliable and run as good or better than the stock 305.

I've got a motor bought as of now. 105k mile motor out of a 97 half ton chevy. Needs head gaskets. So here's my thoughts for right now (subject to change). Put in the marine SS head gaskets, leave the truck cam and valvetrain alone. Edelbrock performer intake and 1409 carb. Bolt on the manifolds and accessories from the 305 and get it ready to be in the water. I'll also check out the lower unit and change fluid while I'm working on it.

The other idea/question that popped into my head, can I use the stock marine cam out of the 305 in the 350? Will it be the same cam as would be in a marine 350? If so, I can pop for new lifters and put the cam from the 305 into it and get a few more free ponies.

stock cam for a 305 is slightly different grind than the 350. you would be better off keeping the truck cam

agree with AD, if your current 105k motor (not really a low mileage motor) needs head gaskets, it most likely needs headwork. the only reason that motor would need head gaskets is that it was run low on coolant and overheated. and yes, the intake manifold gaskets leaking and causing an over-heat is common on the truck motors.
 

gr8shot

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stock cam for a 305 is slightly different grind than the 350. you would be better off keeping the truck cam

agree with AD, if your current 105k motor (not really a low mileage motor) needs head gaskets, it most likely needs headwork. the only reason that motor would need head gaskets is that it was run low on coolant and overheated. and yes, the intake manifold gaskets leaking and causing an over-heat is common on the truck motors.

I will see what it looks like once I get the motor in my hands. Guy has videos of it running. Ran great, just was getting water in the coolant. Supposedly it was in a truck that was getting turned into a show truck so it was pulled to swap for a big block. Not that any of that matters really. But yeah, I'll do my best to check things out when I tear it down. I live in BFE so getting to a machine shop might be tough, but probably worth it to get the heads checked out either way as I have heard they're a little prone to cracking.
 

Rick Stephens

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Don't forget to swap out water pump. Truck water pump will rust out in a few months in water.
 

Lou C

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The ....it needs head gaskets....concerns me....can you take a look under the valve covers to see if there is mayo in there? Because sometimes with head gasket leaks you get glycol in the oil which is very bad for bearings. If no mayo under the valve covers and the oil looks good it may be fine, but if the oil is milky and you are not prepared to go through the whole thing I'd pass.

When I had to replace my head gaskets (and heads due to cracks) I had water in the oil, not glycol but had to act fast to keep changing the oil and draining the water out of the engine until I could take it apart.
 

Lou C

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If the valve covers look like this...it may need all new bearings....
 

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Scott06

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I've got a motor bought as of now. 105k mile motor out of a 97 half ton chevy. Needs head gaskets. So here's my thoughts for right now (subject to change). Put in the marine SS head gaskets, leave the truck cam and valvetrain alone. Edelbrock performer intake and 1409 carb. Bolt on the manifolds and accessories from the 305 and get it ready to be in the water. I'll also check out the lower unit and change fluid while I'm working on it.

The other idea/question that popped into my head, can I use the stock marine cam out of the 305 in the 350? Will it be the same cam as would be in a marine 350? If so, I can pop for new lifters and put the cam from the 305 into it and get a few more free ponies.

Sounds like a fun project

The cam in a 5.0 and 5.7 mercruiser carb engines have the same part number -431-811658 so you could swap the cam and lifters if the oil in old engine isn't water fouled. Alternative I suspect the truck cam will work fine as well.

A couple of other thoughts -

there are cast iron 4 bbl intakes available that might save you $125 vs an edelbrock. The 1409 will work well for this application and is easy to tune based on reading plugs.

If the block was cracked I'd plan on replace the exhaust manifolds and elbows as they likely froze too. I think the flywheel and harmonic balancer are different between the 5.0 and 5.7. If yours came with a stick shift flywheel that will work though.

The 5.0 and 5.7 are typically offered with different drive ratios, very likely you will need to step up 2" in pitch to keep wot rpm in line. When I swapped my 4.3 for a 5.0 for the same reason I kept the 4.3 ratio drive just went from a 19 to 21 pitch.
 

gr8shot

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Water pump is on my list of to-do items for sure.

Is the 811658 for sure the stock cam in a vortec 305? If it is indeed the stock cam, it's at least a little bit of an upgrade from the truck cam. Here's the specs I've been able to find via Google.

Stock L31 truck cam
305/350 Vortec PN 10241264

Intake Duration @ .050: 191
Exhaust Duration @ .050: 196
Intake Lift (w/1.5): 414
Exhaust Lift (w/1.5): 442
Intake Lift (w/1.6): 428
Exhaust Lift (w/1.6): 457
Lobe Separation: 111

811658 Marine 305 and 350 cam

Intake Duration @ .050: 197
Exhaust Duration @ .050: 207
Intake Lift : .430
Exhaust Lift: 450
Lobe Separation: 109

So I think unless the marine cam in the current 305 is junk, I'll swap it and the lifters over as thats easy and free.
 
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