350 Mag engine wake up
 

350 Mag engine wake up
I now have about 60 hours on my Jasper 350 mag and want to wake it up with a cam and set of heads. Any suggestions. Also I thinking about reprogramming the ecu .

Need to talk to someone that has made good running programs for modded 350's and get the parts they used for when they wrote that programming.

If you or someone else is going to tune it on the water ( MEFIBurn is the software one can purchase to do the programming if you have one of the MEFI computers of course.) then many of us can recommend parts depending on your hp goals.

To elaborate what SB said, we'd need a baseline of exactly where your current engine stands in terms of performance, specs and parts.

What pistons/crank do you have?
What is the current compression?
What is your current injector size?

What is your HP goal?

Which ECM do you currently run (MEFI 1, 2 ,3, 4a, 4b, 555, other?)

Do you have a budget or financial number that shall not be exceeded?

put a carbed big block in it.:D

Kind of off subject , but on subject question.

If a 525 SC is basically a 420 with a little blower., what about a small blower on a 350 magnum.

What size blower a250 or a 420. ? And what kind of horsepower you think it would produce?

Just called Jasper Marine and they said they the mercruiser block number OL 316394 for a rebuild.
All the tech said is that is was built to factory specs... The 350 Mag in 99 was a 300hp motor.

I can call proboat to see what they would recommend but I want add a cam and heads to give me 350 or so hp.
They will probably want $2000 to do the work and thats half way to a procharger...

Procharger says that everything is linear so the stock block could take up to 5 psi.

Could not see what ecm I have

'99 350 mag should have vortec heads which are good for up to 400 Hp. If you just want a 50 Hp wake up, a mild cam with around .500 lift, custom tune, and stronger springs with a ghetto grind on the retainers should get you there. But you probably won't even notice a 50 Hp gain.

Spending $12-1500 on a good set of aluminum heads with everything else being stock is not worth it IMO. You'll gain a little on the top end but increasing flow with larger runners will sacrifice torque at lower rpm's, something we don't want to do on a marine engine. It's really hard to beat the stock vortec heads for a stock or mild marine build.

If you want noticeable gains without increasing displacement and you have the budget for it, do a supercharger, long tube headers and through hull exhaust. At that point you also need to make sure your drive is up to the task. By the time you spend that kind of money, you can just buy another boat that has the power you're looking for.

What ?

Don't let the guys with the big and old boats suck you into this thought .

50hp will be more than noticeable on a good running (already) smaller I/O.

My hull's not as fast but I'm in the same age range and weight.

I'd rather have the torque than Hp and, to me, 50 Hp ain't much but I guess that's subjective. My wife would notice a 2-3 mph increase but I don't. LOL When I'm testing it takes a GPS for me to tell if I'm going any faster or slower if we're only talking 2-3 mph. I can't notice a difference between 52 and 54 but I can notice a difference between 40 and 50.

Right now I'm getting 51 at 4700 rpm, I want to get 60 ish...Will a Alpha 1 Gen II take 400 hp ?

Your should be running faster than that. Those boats with the 5.7 EFI (260-270hp) ran 50-52.

50hp willget you in 60's.

Alpha will live behind 350-400 hp 5.7. Idle (neutral) speed needs to be lower than 800rpm.

GPS or speedo?

Most agree that's a reasonable max. Some have torn em up with less and some have run forever with more. A lot depends on how you treat it and how you maintain it. Take it easy on the holeshots, change the oil regularly, make sure it never runs low, and run a drive shower if you regularly make long runs on plane.

Our 18 Barons ran 58 on radar back in 1978 with a stock 260 with pre Alpha and cleaver . We were 1 mph faster than the 18 Donzis

Reason we radiated them was Merc came down with a gun and a trailer full of props after we installed a 280 with a TRS that we complained was a dog.

Best we got out of the identical boat with the TRS /280 hp was 53.

I can see a Donzi z22 only doing 52 with 300 horse .that is twice the freeboard and about a foot more beam than the boats I am referring.

This subject has been discussed may times on OSO. Just do a little searching. I've built quite a few Vortec 350/383's to 400 hp and more. The biggest issue is the stock efi intake manifold. Replace that with a good 4bbl intake and carb, correct cam and good exhaust will get you to 400hp. If you want to stay with efi you need to go to an aftermarket efi intake, throttle body and program the ecu accordingly.

Bob

Put an Alpha SS on it and pick up 5 mph or so

no such thing as gen 2 alpha ss. you would be looking at a transom assy swap complete to run an extinct drive. now, it is a Jasper engine. factory specs. WHICH factory? for all you know it is an emissions cam in there. may not even be roller lifters. and they are DEFINATELY cast pistons, crank. Jasper engines are mass produced for durability. they also machine the valve seats in WAY too deep. they cut everything to the max so they don't have to measure anything., or change machine set-ups. all bores .040. valve stems may now be 3/8ths. you need to pull the intake, get a digital caliper and see what you have for lifters and valve lift at the cam.

I have a 350 mag with a whipple charger on it pushing 550hp with a cam piston and the vorteck heads.i am also running a Blackhawk drive running in the 90s

Yup.

A classic small block "top end cam and exhaust kit" Ive seen add anywhere from 50-100HP in a small block with high quality components (AFR/Brodix)

Tune it on a dyno with marine headers/manifold, and drop it in the boat and rock. Tons of guys have a combo in their drawer for this.

I been to at lest 2 dozen dyno session and never yet seen even an expert builder nail on the first tune, but a few jet swap in and outs and kaboom you get the best sth combo can give.

Doing that in the boat is a nightmare, and if something like an intake manifold gasket has a seal problem its a lot harder to deal with in a bilge than on a stand with a guy opposite you with the mill exposed and at chest height you can fix that stuff in minutes.

Whatever it is you do, please show it to us so we can enjoy the fun with you!

UD

Which stock EFI intake do you refer too? There are stock EFI SB intakes and throttle bodies that will suffice for the HP required.

I'm referring to the late model intake. The early 350 mags and 6.2's had a 4 bbl type intake with an adapter for the throttle body which was not too bad, but still about 20-3 0hp below a good aftermarket intake and and the larger 4 bbl type throttle body.

Bob

I'll check and see what intake and throttle body I have and get back to ya'll. I know its is a four barrel style throttle body.Which one is better ?

I did a full build on twin 350 mag mpi's. You need to build the torque on them to get them to spin the prop. Pushing around 600 on each of mine

How can I check to see what intake and throttle body I have ? Right now I'm seeing 4500 rpms also. Is there a good 3 blade prop ? I'm running a Rev4 19 pitch now

stock 350 mag and whipplle
 

Hi Craig, did you mean to say with "stock cam and pistons and vortec heads"? i have been running a super modified 350 mag with a procharger MS1. nothing but trouble . rebuilt it for 3rd time and detonated again as i can t seem to find a re-builder or marine mechanic in my area that can tune the EFI properly . i have a line on a slightly used 350 mag. I would just keep my stainless marine exhaust and and 7 quart baffled oil pan but otherwise not touch the stock. I have been told a Whipple 350 kit can be put on stock to boost it to 465 Hp with good low end torque. Whipple has a stock flashing to tune the EFI chip that works apparently . it does seem to check out, but i wonder if that was your experience and if it still running and reliable.
Thanks for any info

Dalt,

Craig also hangs out on "Donzi Marine Restoration Society" facebook page. He is running 95 mph in his 18' Donzi Classic. No problems with his motor. The Blackhawk drive has a high x dimision also.
Look him up,he will help you with what questions you may have.

Mark Oltjenbruns

Let me know if you want to sell your old motor,I may be interested, Where are you located ?