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Getting Power From A 4-Banger

mikey_d05

mikey_d05

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My dad recently bought a 1969 (I think anyways) Lund fiberglass 20 foot deep hull heavy as fugk fishing boat. It came with the "upgraded" 4 cylinder Inboard/Outboard engine rated at 130 HP. We're trying a different pitch 4 blade prop this season and seeing how it works, but as of last season it was almost unable to get up on plane with two people, full tanks, and a decent amount of gear. I spent entirely too much time fixing up all of the little things this winter and getting it to work right, and I'd like it to be able to get up and go when we're fishing big water and a storm is coming.

I want to swap in a V8 in a junker boat I found, but that would add about 400 pounds to the back of an already stern heavy boat. Do you all have any suggestions on getting more horsepower out of a 3.0 liter 4 banger? Remember this is a marine engine so it's all about top end here. Forced induction is kinda outta the question since I really don't want to rebuild the motor. Does anybody make a hot cam for an old 3.0?
 
mikey_d05 said:
My dad recently bought a 1969 (I think anyways) Lund fiberglass 20 foot deep hull heavy as fugk fishing boat. It came with the "upgraded" 4 cylinder Inboard/Outboard engine rated at 130 HP. We're trying a different pitch 4 blade prop this season and seeing how it works, but as of last season it was almost unable to get up on plane with two people, full tanks, and a decent amount of gear. I spent entirely too much time fixing up all of the little things this winter and getting it to work right, and I'd like it to be able to get up and go when we're fishing big water and a storm is coming.

I want to swap in a V8 in a junker boat I found, but that would add about 400 pounds to the back of an already stern heavy boat. Do you all have any suggestions on getting more horsepower out of a 3.0 liter 4 banger? Remember this is a marine engine so it's all about top end here. Forced induction is kinda outta the question since I really don't want to rebuild the motor. Does anybody make a hot cam for an old 3.0?
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I don't know jack about marine engines. What's the difference from a street engine ?? Anyways, what about something like a 3.4 V6 ?? It's a pretty light weight engine. Just don't know if you could use it in a marine app.
 
If its the engine I think it is, Chevy II 4 cylinder. Merc Marine used to carry upgrade parts for it. Also, I believe you can use SBC head on it and header.Should be same bell housing pattern as SBC, so maybe you can use alum headed SB and keep the weight down.
 
http://www.cliffordperformance.com makes a good marine cam for those engines. check with them.
Also a carb spacer from cfm-tech.com
Will help wake up your 4 banger.

if you have points in the dist a MSD offroad box or converting to electronic ignition will help also.

A 4 blade prop will get you out of the hole faster but you will loose a little speed on top end.
 
Oh and one question. Does the boat have any kind of power trim.?
Really need power trim with a 3.0L.

Also if you are thinking about a V8. you will prolly need a new outdrive too. The old merc outdrives that came with 4cyls usually wont handle a V8. They also have diferent gear ratios.

With some work you can get that 4 banger to push that boat. They are a very good little engine. They put out more power to weight than a stock V8. The post 96 motors are rated at 150 HP. If yours is an eariler model 3.0 you can put a later model head on and gain 15 or more HP. The later heads are 9.3 to one CR and the ports are straighter. If you want to spend the money You can change over to TBI too. But you wont gain a whole lot of HP over a carb. TBI builds torque quicker and will will get you out of the hole faster tho.

I have a slightly modified :wink1: 2.5 l Mrecruiser in my 17.5 foot deep V fiberglass fish/ ski boat. I can get on plane with a full load no problem. I like the 4 banger better than the 20' V8 boat I used to have. I use my boat mostly for fishing now that my kids are grown. The 4 banger is a lot cheaper to run all day fishing than my old gas hog 350. It's not as fast as my old V8 but My boat does about 42 MPH with 2 guys + gear at 5000 feet ELE. It is a lot faster at sea level. I can fish/troll all day on 8 gal of gas. I use my boat on big water too. The pacific ocean is about as big as water gets.

If you have any questions go ahead and ask. I know a thing or two about these little engines.
 
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Well I talked to a career boat mechanic today and he said that with a new cam, head, intake, and carb I'd only end up gaining about 10 hp and almost no torque. I find that pretty damn hard to believe. To make a long story short, if I went to anything other than an inline engine, I'd have to get a new outdrive (see $$$) because of the exhaust setup. A v-motor's outdrive is set up differently because of the exhaust routing. I'm not looking for 100 miles an hour here, but this boat is real heavy and I'd like to run a more agressive 4 blade so I can get it up on plane and run at a decent speed if I need to. My dad and I fish Mille Lacs and and two of the great lakes so being able to head for shore on command is definitely neccessary. Not quite like the Pacific Ocean, but big enough to drown a 20 footer with ease. If there is a total rebuild kit available for this engine more oriented towards performance (which I kinda doubt) what do you think I could get out of the motor? I'm thinking the newer style head and 150 hp would do fine, but is there a good way to bump it up to 160 or 170 without tearing it apart? I don't honestly know much when it comes to these Chevy II motors so forgive me if there's an ignorant remark in there. Thanks for your help.
 
Oh yeah, what do you mean by power trim? The outdrive has power trim but the boat doesn't have trim tabs. Dunno which one you're referring to. I could try a set of trim tabs to force the nose down and push it up on plane, but putting a ton of holes in fiberglass isn't my idea of fun.
 
You really wont be able to get much more reliable HP than 150 out of the 3.0 L. You could probabally build one to make more but it may go Boom. Those motors dont like high revs. I would not take one much over 4800 for any long period.

With a 150 hp you will get around 135 Hp at the prop. That should be plenty to move your boat. Do you have a tachometer on the boat? Check your RPM at WOT you should be able to hit around 4800. If you cant then you need a prop with less pitch. A 4 blade prop will definatly help you. As long as you get the right pitch.
For example If you can only get 4400 RPM out of your boat, dropping the pitch 2" will give you 400 more RPM on the top. bringing your max rpm to 4800. It will also give better low end performance, because a lower pitch prop allows your engine to get to its operating range faster. Where it devlopes the most HP. You gain 150-200 rpm for every 1" of pitch you go down. A ventelated prop will also help your engine get to its power band quicker.


Ok. Your outdrive has power trim. You need to use it to get your boat out of the hole. Should be all the way out when you start off. Then trim it in as you come up on plane. Putting on a trolling plate will also help to get your boat up on plane faster. My boat planes a lot faster with a troling plate. Trim tabs also help but they probabally wont help enough to justify the cost. The hydraluic ones are pretty expensive.

Before you spend a bunch of money on your engine.The first thing I would try to do to your boat is: Get it proped right.Try to find a prop that will get you to your max operating speed (Around 4800 RPM). If you cant reach max RPM with the prop you have. You are over propped and need to go down in pitch
If you dont have a trolling plate get one like a happy troller or similar. They will help get on plane and are handy if you want to go a real slow trolling speed.
 
There's a tach on the boat but it's redline is at 3,600 RPM. I don't like to take it much higher since the valves don't sound the greatest but I think that might be from some old, low octane unleaded that some genius put in there. I don't know what pitch the new prop is since (unfortunately) I wasn't involved in that decision. I normally did the trimming method that you described with our old boat, but it had a much better power to weight ratio. Even with that technique it's difficult to get it up out of the water. It's getting a few minor things done to it this week and then we're going to take it for a test run, and I'll go from there. Thanks for all your help, I really appreciate it.

-Mike
 
Just thought I'd let you know the operating range on 3.0s is 4200-4800 RPM.
If it is a upgraded 3.0 as you said it can handle 4800 no problem.
your engine should be able to get you up that high at wide open throttle for best performance.
3600 is not enough RPM. Espically in a big boat. You have to be able to get up higher to make power. Get your motor over 4k rpm and you will see better performance. Check youe timing. If the valves are making noise maby they need adjustment. 4000+ is not a lot of RPM for a marine engine they are built to do it
 
Strange thoughts in my head , even though I ain't a ford man , how about a junkyard turbo and plumbing from a Thunderchicken with a 4 banger . You would need top fab a bunch of stuff to fit it and figure out a cam .

I remember a cheap 10 second Pinto with a 2.3 ford with Thunderchicken stuff in Car Craft in the 90's .

My boat has a 4 cylinder Chrysler/Volvo and I am gonna live with it until I win the lottery and buy a Bass Boat .
 
Was thinking about the noise you said it was making.
Are you sure it is not pinging? Because marine engines operate at high RPM Detonation is a problem with marine engines. Like auto engines pinging is very bad for them and is a good indacator something is really out of tune.

Make sure of the following;

Timing is set right. There should be a tag on the engine that tells where to set it. But 8 degrees should be close enough. I run mine at 10-12 but i live at high elevation.

Carb is jetted right. if yur at below 5000 ft your jets should be stamped 160 or 165....... Above 5K it should have 155 jets

No vacuum leaks.

Use premeium fuel.

Once again. Use the right prop. Using a prop with too much pitch on a boat. Is like trying to climb a hill in too high of a gear in a car.
 
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