HELP! How to tune a Mercruiser 350? - Hot Rod Forum : Hotrodders Bulletin Board
Hotrodders.com -- Hot Rod Forum



Register FAQ Search Today's Posts Unanswered Posts Auto Escrow Insurance Auto Loans
Hot Rod Forum : Hotrodders Bulletin Board > Tech Help> Engine
User Name
Password
lost password?   |   register now

Reply
 
LinkBack Thread Tools
  #1 (permalink)  
Old 11-12-2003, 10:31 AM
Registered User
 
Join Date: Nov 2003
Location: Sweden
Posts: 4
Wiki Edits: 0

Thanks: 0
Thanked 0 Times in 0 Posts
Post HELP! How to tune a Mercruiser 350?

Hi,

I am sorry if this is a bit off topic. I have a Chevy Blazer K5 at home also....

I have bought a boat in August without engine. Now I am about to build one. I have a Mercruiser block (Chevy 350), I think with 1:9,5 compression and a Rochester Quadrajet carb.

My stern drive is a Mercruiser Alpha One 1:1,5 (exhaust through the stern drive).

My problem is that this boat (weight 4800 lb) is known to be a very gasoline consuming one, and the fuel price is high in Sweden. Our petrol price is 4.6USD/gallon!, so I want my engine to be so fuel effective as it can.

A modern Volvo Penta 330GXi (330HP Chevy 350 with fuel injection) takes about 0.35gallon/mile in this boat, and that is good. I am glad if my engine will do that.

Max rpm should be about 4600rpm and my guess is that cruising speed will be at 3300-3500rpm (35mph). Max speed will hopefully be about 45mph.

I have been given the following suggestions:

Get a dual plane Edelbrock Performer inlet manifold (not the "RPM" though) and a Crane 113901 came shaft
http://www.cranecams.com/motorsports/sbchevy/113901.htm or perhaps a Crane 113971
http://www.cranecams.com/motorsports/sbchevy/113971.htm or perhaps a Crane 109811


or a CompCamp Xtreme Marine: 12-232-3 (good fuel economy) or: 12-236-3
http://www.compcams.com/Technical/Ca...L/128-169.html


Which of the cams (or another cam) should I get? Is there anything else I could do to get much torque at low and mid rpm (I guess I need the torque from 1200-1300rpm) and still get a decent fuel economy?


Thanks!

Jake

    Advertisement

Last edited by Jake Plisken; 11-14-2003 at 12:06 AM.
Reply With Quote Quick reply to this message
Sponsored Links
Advertisement
 
  #2 (permalink)  
Old 11-12-2003, 11:07 AM
Tow_Truck's Avatar
Registered User
 
Join Date: Nov 2003
Location: London, Blighty
Posts: 3
Wiki Edits: 0

Thanks: 0
Thanked 0 Times in 0 Posts
Try a diesel!!

Hi Jake

Can't help with the cam question, but have you considered putting a diesel in?
I live in the UK and fuel is about $6 a gallon so I know where you're at. In my boat I had the same situation, I fitted a 6.5 diesel chevy motor in. The engine is a straight swap for the 350 chevy. Just physically a little bigger, but all the mounts line up, as does the bell housing and shaft fittings. You do need different exhaust manifolds though.
On paper it sounds like a poor swap, the petrol is much quicker at the top end. But in reality the boat loses about 5-7 mph from the top end but gains 3-4 mph at cruising speed. Resistance through the water increases very rapidly with speed so that extra power is absorbed in a short speed range. A diesel has massive torque and is happy to cruise at 85%+ of its rpm limit. Most petrols cruise at 60% of the rpm limit, normally less due to economy considerations.
These engines also respond well to supercharging and will out perform a normally aspirated 350 chevy in the marine enviroment.
Diesels are much more reliable than petrol engines especially in the presence of water! The fire risk is also much reduced.

Running petrol:
Max=33knts
Cruise=17knts
Fuel=10 gallon/h

Running diesel:
Max=25knts
Cruise=20knts
Fuel=3 gallon/h

Faster cruising and a 70% reduction in fuel consumption!!

In the UK we can use duty free diesel in boats which is only $1.60 a gallon. (I can normally 'find' enough free for an entire season).

Just my two euros worth.

Hmmm,, wonder if I could squeeze one in my 'Stang??
Reply With Quote Quick reply to this message
  #3 (permalink)  
Old 11-12-2003, 11:52 PM
Registered User
 
Join Date: Nov 2003
Location: Sweden
Posts: 4
Wiki Edits: 0

Thanks: 0
Thanked 0 Times in 0 Posts
Diesel,... That's a thought. Unfortunately we don't have that tax reduced marine diesel. Our diesel costs about 3.9 USD/US gallon (= 4.7 USD/British gallon) You make it sounds like a good alternative. But I guess that though have to be until at least next season. I have to build my petrol engine first (I do have all equipment except cam and inlet manifold).

Please give me feedback to my specification questions!

Jake
Reply With Quote Quick reply to this message
  #4 (permalink)  
Old 11-13-2003, 12:06 AM
Member
 
Last photo:
Join Date: May 2003
Location: Shreveport LA
Age: 64
Posts: 5,103
Wiki Edits: 0

Thanks: 0
Thanked 0 Times in 0 Posts
Is the block a later-model one that is set up for use with a factory hydraulic roller cam?
Reply With Quote Quick reply to this message
  #5 (permalink)  
Old 11-13-2003, 12:10 AM
Registered User
 
Join Date: Nov 2003
Location: Sweden
Posts: 4
Wiki Edits: 0

Thanks: 0
Thanked 0 Times in 0 Posts
No, I think the block is an older one, perhaps late 70's or early/mid 80's.

Jake
Reply With Quote Quick reply to this message
  #6 (permalink)  
Old 11-13-2003, 08:36 AM
Wrencher's Avatar
Member
 
Last photo:
Join Date: Aug 2003
Location: cincinnati
Age: 56
Posts: 607
Wiki Edits: 0

Thanks: 5
Thanked 0 Times in 0 Posts
Jake, I'd move to the U.S.! LOL, I have a 24' 5000lb. boat 89 w/ 350/260h went to 355, 420h and I don't really notice much change in mileage, except of course with your foot " hand" in it! 63+mph@ 6300, those q-jets are pretty conservative @ cruising speeds. Just MO
Reply With Quote Quick reply to this message
  #7 (permalink)  
Old 11-14-2003, 12:36 AM
Registered User
 
Join Date: Nov 2003
Location: Sweden
Posts: 4
Wiki Edits: 0

Thanks: 0
Thanked 0 Times in 0 Posts
Tow_Truck, it sounds almost unbelievably big difference between diesel and petrol consumption. 3 instead of 10 gallons per hour!
Was this at cruising speed? Can the difference also due to other facts (plane threshold)?

Can I use the same stern drive 1:1,5? Or should I have i rebuilt (is it possible to rebuild a Mercruiser Alpha One, gen 1?)

Supercharging... are we talking about turbo or compressor? How much for a supercharger for marine application? I guess the diesel consumption will increase a bit now.... And I guess I have īto rebuild the engine with lower compression....!?

Thanks!

Jake

Last edited by Jake Plisken; 11-14-2003 at 08:03 AM.
Reply With Quote Quick reply to this message
  #8 (permalink)  
Old 11-14-2003, 08:01 AM
Member
 
Last photo:
Join Date: Oct 2003
Location: Tri-Cities, TN
Posts: 726
Wiki Edits: 0

Thanks: 0
Thanked 0 Times in 0 Posts
Jake,
I would go to reedcams.com. The have a series
called the Torque Master and they are the best
marine cams. I would put the Lobe sep on a 114 put
4 degrees of advance in the cam 110 ICA. Intake
I would go with a dual plane with a 1" spacer. If you e-mail reed talk to Dennis, he may be able to get you everything and
save you some freight.

Cstraub

One other thing, with the problem that we have
had with lifters, I would highly recommend getting the
micro finish process on the cam and lifters. It might
be a 100$ extra but its well worth the money as compared
to pulling the engine and putting another cam in it.

Cstraub

Last edited by Cstraub; 11-14-2003 at 08:01 AM.
Reply With Quote Quick reply to this message

Recent Engine posts with photos

Quick Reply
Message:
Options

Register Now

In order to be able to post messages on the Hot Rod Forum : Hotrodders Bulletin Board forums, you must first register.
Please enter your desired user name (usually not your first and last name), your email address and other required details in the form below.
User Name:
Password
Please enter a password for your user account. Note that passwords are case-sensitive.
Password:
Confirm Password:
Email Address
Please enter a valid email address for yourself.
Email Address:

Log-in

Human Verification

In order to verify that you are a human and not a spam bot, please enter the answer into the following box below based on the instructions contained in the graphic.




Currently Active Users Viewing This Thread: 1 (0 members and 1 guests)
 
Thread Tools

Posting Rules
You may post new threads
You may post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are On
Pingbacks are On
Refbacks are On



All times are GMT -6. The time now is 03:11 AM.


Powered by vBulletin® Version 3.8.7
Copyright ©2000 - 2014, vBulletin Solutions, Inc.
Search Engine Optimization by vBSEO 3.6.0 PL2
Copyright Hotrodders.com 1999 - 2012. All Rights Reserved.