What makes a marine engine a MARINE engine

[270win]

Re: What makes a marine engine a MARINE engine

Isn't the performer RPM intended to yield the most power from 1500-5500 rpm, where the performer is for 0 rpm on up? Seems like the performer would be better for a boat if what I stated is true. Well maybe not 0, but lower rpm.

with what you're taking about you shouldn't see a difference from 0-1500 rpm. But in my experience, the RPM is better for midrange and top end numbers.

It'll smoke that 305 at any rpm...

 

[BigBoatinOkie]

Re: What makes a marine engine a MARINE engine

Well in that case, my brother just happens to have a performer rpm that needs a home.

 

[Alpheus]

Re: What makes a marine engine a MARINE engine

Don't listen to what they say about the valves. They are the same darn thing that are in a truck engine. I just got into an argument with a guy at work who kept telling me that marine engines have totally different cooing passages and that the cylinder walls were thicker. I dont know about the marine engines of old, but as far as what Mercruisers are using now, it is 100% an automotive long block with brass freeze plugs...

As for the Q-Jet carb? It comes down to people fear what they don't understand. Just watch the video I made about rebuilding a Q-Jet carb and you will see that there is nothing magical inside. Its a cut and dry carb that works...

 

[270win]

Re: What makes a marine engine a MARINE engine

Well in that case, my brother just happens to have a performer rpm that needs a home.

Just make sure the bolt pattern is right for whatever engine you end up with.

Performance Products also makes an intake that will work with both Vortec and sbc heads. They're cheaper than the Edelbrock stuff too...

 

[fishrdan]

Re: What makes a marine engine a MARINE engine

The Performer intake will put the power band at off idle, where you want it in a boat, starting at 1500RPM doesn't sound like a good match for a marine engine. I've heard some say don't use an aluminum manifold on a marine engine and others that say they haven't had problems. Personally, I wouldn't use an aluminum manifold on a marine engine since you don't have antifreeze protecting the metal. Heck I had an aluminum manifold start corroding on my old hot rod, minimal, but it was still corroding while being protected by antifreeze.

I wouldn't shy away from a Carter AFB, Edlebrock, Weber (what ever we want to call it today) carb. I've had a few and thought they performed great and were easy to work on. With a Strip Kit (jets, springs, needles) they are pretty easy to dial in. And if there was a problem, they were quick and easy to get into.

One thing I've learned though,,, high performance does not necessarily equal high reliability. For my boat's engine I'm not straying far from Mercruiser specs...

 

[ckgreenman]

Re: What makes a marine engine a MARINE engine

Isn't the performer RPM intended to yield the most power from 1500-5500 rpm, where the performer is for 0 rpm on up? Seems like the performer would be better for a boat if what I stated is true. Well maybe not 0, but lower rpm.

If it were me I'd stick with the Performer. That's the same manifold I used to run on my Camaro, I believe the power curve for it was off idle to 4500. Plus I think the stock bowtie manifold on the Mercruiser is essentially the same design as the Performer.


EDIT: Oops just looked it up. The Performer is off idle to 5500. the Performer RPM is 1500-6500.

 

[270win]

Re: What makes a marine engine a MARINE engine

The Performer intake will put the power band at off idle, where you want it in a boat, starting at 1500RPM doesn't sound like a good match for a marine engine. I've heard some say don't use an aluminum manifold on a marine engine and others that say they haven't had problems. Personally, I wouldn't use an aluminum manifold on a marine engine since you don't have antifreeze protecting the metal. Heck I had an aluminum manifold start corroding on my old hot rod, minimal, but it was still corroding while being protected by antifreeze.

How long does it take our boat engines to transition from an 850 rpm idle in gear to past 1500 rpm? We're talking maybe 1/2 a second if you stab it...in a small pleasure boat, you're not going to see an appreciable difference. But if you're running along on plane at 2500 rpm, and you nail it, how long does it take to get to WOT? That's where you want the most torque and responsiveness. Maybe in a drag boat or a dedicated ski boat this would matter...I'd say this much, if you have a performer RPM laying around, I wouldn't pass it by to go guy a Performer.

I wouldn't shy away from a Carter AFB, Edlebrock, Weber (what ever we want to call it today) carb. I've had a few and thought they performed great and were easy to work on. With a Strip Kit (jets, springs, needles) they are pretty easy to dial in. And if there was a problem, they were quick and easy to get into.

I agree, but I feel that a Q-jet is superior all around...once it's dialed in.

One thing I've learned though,,, high performance does not necessarily equal high reliability. For my boat's engine I'm not straying far from Mercruiser specs...

I agree, I'm a big fan of OEM stuff too. I think as far as hp goes, if you stay down around 300 or less, you're really not pushing a 350 at all.

 

[270win]

Re: What makes a marine engine a MARINE engine

Oh, about the corrosion issue, I've always found that the aluminum intakes get pretty nasty quickly. I found a solution but it does change the original appearance. I sand blast the intake to clean it. (be sure to completely clean out ALL blasting media) I like to hang the intake up from a coat hanger or similar wire. Then I paint it with several coats of clear VHT paint.

Here's the vortec 400hp 355 I've been referring to, I used VHT on the intake.

Here it is after two years of street driving and drag strip use-

EDIT: Changed HUGE picture to link so people don't have to scroll to read the replies.

Link removed so everyone and their brother doesn't have access to my photobucket pages.

The pic showed up the same size as the above pic on my computer...sorry about the large pic-
Anyway, it looks the same...

 

[fishrdan]

Re: What makes a marine engine a MARINE engine

How long does it take our boat engines to transition from an 850 rpm idle in gear to past 1500 rpm? We're talking maybe 1/2 a second if you stab it...in a small pleasure boat, you're not going to see an appreciable difference. But if you're running along on plane at 2500 rpm, and you nail it, how long does it take to get to WOT?

But, what about 1500-2500RPM, when the boat is plowing through the water and trying to climb on plane? That's when you want the engine well into it's power band so it can pop onto plane quickly. The Performer is right in that sweet spot, while the Performer RPM is barely coming into it's effective RPM range. Since the targeted WOT RPM of a Mercruiser engine is somewhere around 5000RPM or less, I don't see how a manifold with a top end of 6500 would be useful for most rec boaters. Twist the engine up that high and the outdrive could start having some serious problems.

At 2500 RPM Edelbrock shows thier Performer intake makes 360ftlb while the Performer RPM only makes 330ftlb of torque, 10% more torque for the plain ol' Performer intake. But here's the kicker, the Performer has the same torque of 330 ftlb at 2000RPM, as the Performer RPM at 2500RPM. I'd rather have extra torque while the boat is fighting to come on plane, than at near WOT. Sure, a marine engine isn't going to have these same numbers because of cam/carb/exhaust/etc, but I'd venture to say the percentages are about the same.

I boat at high altitude and the problem RPM is right at 2000-2500RPM when the boat is trying to pop on plane, anything below or above that, no problem. The first I ran my boat at 9000' I would have given my left (___) for 10% more torque

 

[270win]

Re: What makes a marine engine a MARINE engine

But, what about 1500-2500RPM, when the boat is plowing through the water and trying to climb on plane? That's when you want the engine well into it's power band so it can pop onto plane quickly. The Performer is right in that sweet spot, while the Performer RPM is barely coming into it's effective RPM range. Since the targeted WOT RPM of a Mercruiser engine is somewhere around 5000RPM or less, I don't see how a manifold with a top end of 6500 would be useful for most rec boaters. Twist the engine up that high and the outdrive could start having some serious problems.

At 2500 RPM Edelbrock shows thier Performer intake makes 360ftlb while the Performer RPM only makes 330ftlb of torque, 10% more torque for the plain ol' Performer intake. But here's the kicker, the Performer has the same torque of 330 ftlb at 2000RPM, as the Performer RPM at 2500RPM. I'd rather have extra torque while the boat is fighting to come on plane, than at near WOT. Sure, a marine engine isn't going to have these same numbers because of cam/carb/exhaust/etc, but I'd venture to say the percentages are about the same.

I boat at high altitude and the problem RPM is right at 2000-2500RPM when the boat is trying to pop on plane, anything below or above that, no problem. The first I ran my boat at 9000' I would have given my left (___) for 10% more torque

At 9000' I'm sure that's a BIG issue, you're probably down to 60-70% of your rated HP...plus 10% is HUGE assuming the percentages are the same. This is, again, where the complete setup is important. That intake will react differently to different engine setups...cam, heads, etc.

BUT, if I'm right and it's a small difference for the RPM in the midrange and top end, it's also only a small disadvantage for the Performer at midrange...IF the bottom end is that crucial then go with the other one.

What size boat is this going in...I forget...All of the above options will outperform the 305 by a long shot.

 

[Don S]

Re: What makes a marine engine a MARINE engine

270win
You seem to be giving a lot of advise for someone that really doesn't understand marine engines that well. You may know a lot about the automotive side and racing, but I don't see any knowledge showing through about the marine side of things. And that is what this forum is about. MARINE, not GTO's and race engines. So just be careful what you are saying. You haven't given any thought about reversion have you?

 

[BigBoatinOkie]

Re: What makes a marine engine a MARINE engine

One thing I've learned though,,, high performance does not necessarily equal high reliability. For my boat's engine I'm not straying far from Mercruiser specs...

Yes, I definately want good reliability. I'm not really looking for "high" performance, reliability is the key still.

How long does it take our boat engines to transition from an 850 rpm idle in gear to past 1500 rpm? We're talking maybe 1/2 a second if you stab it...in a small pleasure boat, you're not going to see an appreciable difference. But if you're running along on plane at 2500 rpm, and you nail it, how long does it take to get to WOT? That's where you want the most torque and responsiveness. Maybe in a drag boat or a dedicated ski boat this would matter...I'd say this much, if you have a performer RPM laying around, I wouldn't pass it by to go guy a Performer.

It's not a mastercraft or ski natique but most of the time my boat is towing folks. Myself and several of my family are 250 to 300 lbs, so low RPM power is quite important to me. It's quite a chore to pull up fat guy on a slalom ski.

At 2500 RPM Edelbrock shows thier Performer intake makes 360ftlb while the Performer RPM only makes 330ftlb of torque, 10% more torque for the plain ol' Performer intake. But here's the kicker, the Performer has the same torque of 330 ftlb at 2000RPM, as the Performer RPM at 2500RPM. I'd rather have extra torque while the boat is fighting to come on plane, than at near WOT. Sure, a marine engine isn't going to have these same numbers because of cam/carb/exhaust/etc, but I'd venture to say the percentages are about the same.

Yes, and my hull is not really great getting on plane. I have bennet trim tabs, but they don't work at the moment. Once I get em fixed, and add a little more torque and hp, it ought to get on plane in a heartbeat. She rides like a dream once on plane though and cuts through chop like butter. My dad always has to follow along in my wake on choppy days (which is most days here in OK) in his little bayliner.

 

[fishrdan]

Re: What makes a marine engine a MARINE engine

Myself and several of my family are 250 to 300 lbs, so low RPM power is quite important to me. It's quite a chore to pull up fat guy on a slalom ski.

Yes, and my hull is not really great getting on plane.

Sooo, are you looking to replace/rebuild your engine because it's tired or because of poor boat performance? A lower pitched prop could do wonders for the hole-shot / planing time of your boat, and be a heck of a lot cheaper and easier than an engine.

I swap props for different applications, 19P for general use, 17P for heavy loads/skiing or up at 5000',,, and in the works is a 15P for 9000' because the 17P just won't cut it up there.

 

[270win]

Re: What makes a marine engine a MARINE engine

270win
You seem to be giving a lot of advise for someone that really doesn't understand marine engines that well. You may know a lot about the automotive side and racing, but I don't see any knowledge showing through about the marine side of things. And that is what this forum is about. MARINE, not GTO's and race engines. So just be careful what you are saying. You haven't given any thought about reversion have you?

Reversion? What are you saying, Don? I think that my experience does qualify me to give advice on engine basics. If someone disagrees they don't have to follow it. I'm simply trying to help someone come up with a solid combination to meet their goals...I thought that was what this forum, and more particularly, this thread, was about.

 

[Don S]

Re: What makes a marine engine a MARINE engine

Reversion? What are you saying, Don?

Just what I said, you understand reversion on marine engines don't you? Aka valve overlap, wet exhaust, water in cylinders, and all that good stuff?

I recall one of your posts saying you're not familiar with marine engines, but yet you are giving very specific advise on things. That may or may not work.

 

[John_S]

Re: What makes a marine engine a MARINE engine

FWIW: Zinc chromate primer and Merc black has held up very well on my performer intake.

 

[270win]

Re: What makes a marine engine a MARINE engine

Just what I said, you understand reversion on marine engines don't you? Aka valve overlap, wet exhaust, water in cylinders, and all that good stuff?

I recall one of your posts saying you're not familiar with marine engines, but yet you are giving very specific advise on things. That may or may not work.

OK, I was wondering if you were talking about Reversion, as in -the act of reverting; return to a former practice, belief, condition, etc.

Wanted to make sure you weren't asking me to go back to the car forums or something of that nature...

Which of the intakes we're discussing are going to cause any more adverse exhaust pulses coming back into the exhaust port? Or are you talking about the cam advice? All are marine grinds from Comp, Lunati or MerCruiser. Or the advice to stick with the original Q-jet rather than an aftermarket carb.? Or the advice to get a long block from Rapido? Or taking the entire engine combination into consideration before deciding on one particular component. I'm pretty sure all of this is solid advice...

If you only want input from marine engine guru's or MCM certified technicians, then that's fine. But if that's the qualification to give advice or share opinions here, most of the responders on this thread aren't qualified either. Why is my advice is being scrutinized like this???

 

[Bifflefan]

Re: What makes a marine engine a MARINE engine

the same thing that makes it a racing engine.... MONEY!!!

 

[fishrdan]

Re: What makes a marine engine a MARINE engine

My concern with aluminum intakes isn't with the exterior of the manifold, it's the interior water passages. The automotive intake I had problems with (Edelbrock, Wieand? don't remember anymore) looked fine on the outside, but had corrosion inside the water passages. I'm sure if this intake were on a marine engine the corrosion would have been much worse, and left unchecked for a long time, could have possibly eaten through and leaked water into the oil. An ol' machinist I know looked at the manifold and commented "they don't use the best aluminum alloy to cast those manifolds out of", I took his comment as they used cheap aluminum. Probably good enough for an engine running antifreeze, but I have reservations with raw water cooling.

Eh, outboards are built out of aluminum and don't suffer from too many catastrophic corrosion problems, but then again, they are most likely built out of superior aluminum alloys.

 

[270win]

Re: What makes a marine engine a MARINE engine

My concern with aluminum intakes isn't with the exterior of the manifold, it's the interior water passages. The automotive intake I had problems with (Edelbrock, Wieand? don't remember anymore) looked fine on the outside, but had corrosion inside the water passages. I'm sure if this intake were on a marine engine the corrosion would have been much worse, and left unchecked for a long time, could have possibly eaten through and leaked water into the oil. An ol' machinist I know looked at the manifold and commented "they don't use the best aluminum alloy to cast those manifolds out of", I took his comment as they used cheap aluminum. Probably good enough for an engine running antifreeze, but I have reservations with raw water cooling.

Eh, outboards are built out of aluminum and don't suffer from too many catastrophic corrosion problems, but then again, they are most likely built out of superior aluminum alloys.

Sorry, I thought you were primarily concerned about appearance.

We run water only in our race engines. Disclaimer: Drag car, NOT marine engines... but anyway, we run water only because antifreeze is much more slippery and difficult to clean if you get it on the track.

Anyway, I haven't noticed any corrosion...could be due to the limited time on drag engines rather than higher hours put on boat engines...I wonder if the cooler raw water supply in a boat has anything to do with breaking down the aluminum in the intakes we're talking about? Or, could it just be lousy quality aluminum castings? Does antifreeze with polyethylene glycol preserve aluminum?