Horsepower Rating on 1991 OMC King Cobra 350 with "Bowtie" Highrise intake?

Ericmdoman

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Hi everyone, I am new to Iboats and this forum and am hoping someone can help. I recently purchased a 1991 Dynasty Elan 208 from a family member. Boat has been in family for years and is in great shape, however, there has always been a discussion on the exact HP rating of the boat. To me, this is important as I am changing props this spring and want to choose the right prop based on my HP rating and RPMs I am pushing. I have the original service manual 1991 King Cobra outdrive but it doesnt help me either. Boat has the original OMC 350 King Cobra outdrive with a Chevrolet Small Block 350. From what I can find on the net, it either has 260 HP or 300HP. Considering it has the High Performance "Bowtie" Chevrolet High Rise intake on it, I am leaning towards the 300HP. I have Serial numbers for the intake and engine itself below but I have yet to reach a conclusion.
The intake is the GM 14096242 Bowtie Highrise intake with a date stamp of 08-26-87. From what I can find, this was somewhat of a rare intake that was Cast Iron, high rise for 4 barrell and built specifically for performance.

The Serial numbers on the Engine itself (front left above flywheel) have me somewhat stumped.....
V01058A5
T1069434

GM 5.7 LG is stamped on the backside of the block.
I really cant find any specific info on the block itself which would give me an actual HP rating. Thought someone in this blog might have some experience or knowledge more than myself. Thanks in advance!!
 

Bondo

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Hi everyone, I am new to Iboats and this forum and am hoping someone can help. I recently purchased a 1991 Dynasty Elan 208 from a family member. Boat has been in family for years and is in great shape, however, there has always been a discussion on the exact HP rating of the boat. To me, this is important as I am changing props this spring and want to choose the right prop based on my HP rating and RPMs I am pushing. I have the original service manual 1991 King Cobra outdrive but it doesnt help me either. Boat has the original OMC 350 King Cobra outdrive with a Chevrolet Small Block 350. From what I can find on the net, it either has 260 HP or 300HP. Considering it has the High Performance "Bowtie" Chevrolet High Rise intake on it, I am leaning towards the 300HP. I have Serial numbers for the intake and engine itself below but I have yet to reach a conclusion.
The intake is the GM 14096242 Bowtie Highrise intake with a date stamp of 08-26-87. From what I can find, this was somewhat of a rare intake that was Cast Iron, high rise for 4 barrell and built specifically for performance.

The Serial numbers on the Engine itself (front left above flywheel) have me somewhat stumped.....
V01058A5
T1069434

GM 5.7 LG is stamped on the backside of the block.
I really cant find any specific info on the block itself which would give me an actual HP rating. Thought someone in this blog might have some experience or knowledge more than myself. Thanks in advance!!

Ayuh,.... Welcome Aboard,.... It was probably rated 275 hp or so, maybe 300,....

But, yer goin' at it backwards,.....
Yer prop is exactly like a Dyno,...
Ya prop the thing to run 4800 rpms, at Wot, proper trim, average load, to calculate backwards to come up with the True Horsepower of yer motor,....
 

jerryjerry05

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It sounds like someone's replaced the intake.
So there's no way of knowing what else was done???
A stock 91 was 260-280hp.
The "King Cobra" was just a name they stuck on a bunch of motors.
They even used the KC sticker on the 2.3L Ford.
Like Bondo said the prop needs to be selected by RPMs.
The numbers below are the 4 series made that year. 574APERGD
574APLRGD
574APRRGD
574BPERGD


One good thing. Your drive is the cone clutch drive and real dependable.
 

Ericmdoman

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Hey guys, I appreciate the responses. Bondo, I should have been more a little more detailed and I understand exactly where you are coming from regarding the prop. Like you said, according to the King Cobra service manual, I shouldnt be above 4600rpm WOT. As Jerry said, the "King Cobra" was put on several motors but basically a description of the Outdrive. As Bruce mentioned, I havent had problems getting parts except replacing the original factory trim motor. My bro in law had the boat the last 5 years and as far as I know the motor is all original including the intake. From my research, that intake was factory for several high performance motors through those years. He had the motor rebuilt 3 years ago (nothing special, back to original specs) as the motor threw a rod and switched from the OEM distributor setup to an MSD ignition. The tachometer never worked since he owned and he never had it fixed........so he threw the MSD ignition/distributor on it and set the Rev limiter to 4500 rpm while running a 17 pitch Mercury "High 5". I only ran it a couple times this summer with this setup...it would come out of the whole pretty quickly with me and 3 others on the boat, but it would only top out at about 45mph.

I ended up having Carb issues and replaced the Rochester 800 cfm Quadrajet with a Holley 650 cfm quadrajet which my marina mechanic cross referenced with Summit Racing for my motor. I also removed the MSD setup and went with the original normal distributor setup and got my tach working. Its a beautiful 91 model boat and I want to stay as close to factory as I can.

I bought a Solas 4 blade SS 21 pitch just for starters after the work was done because I wanted more top end. It was a complete failure.......was way too much prop for the boat. With me and my wife on there.....It took forever to come out of the hole and would run only 3500rpm WOT at 50mph. I am trying to find a happy median so to speak and am wondering if a 3 blade 17-18 pitch might do the trick..........Unfortunately, I think I am just going to have to play around with different props and see what RPMs Im running at WOT and see how I do out of the hole. The reason I question HP rating is, the owner of the shop I deal with (who used to be an OMC dealer) said it should be 260HP, however his mechanic said it is 300HP because of the "Bowtie" intake. He said any of those 350 engines with the "bowtie" intake should be 300. I was just trying to find someone who might know for sure............thanks again
 

bruceb58

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How did the person who changed the distributor get the ESA to work properly?

edit: I see you went back to the original distributor.
 
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Bondo

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The reason I question HP rating is, the owner of the shop I deal with (who used to be an OMC dealer) said it should be 260HP, however his mechanic said it is 300HP because of the "Bowtie" intake. He said any of those 350 engines with the "bowtie" intake should be 300. I was just trying to find someone who might know for sure............thanks again

Ayuh,.... I'd believe the marina owner, over his mechanic, All day long,.....

Ya don't get 40 hp, from a manifold that's merely 3/4" taller,....
 

Maclin

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My Volvo Penta 570/DP, same as AQ271C, has the "factory' high rise cast intake, it is 275HP. There is a version of it that has 290 with different cam. But 300HP is a stretch without more mods than that. A performance aftermarket "higher" highrise raises the RPM power band, not all that desirable in a Marine app.
 
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Ericmdoman

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Bondo, I am with you on that one.......It has been kind of hard for me to believe 300HP could come out of a Factory 1991 350. The problem was that I had 3 different people telling me different things at the shop. Owner says 260hp, his son (who works there as well) and the mechanic told me 300Hp.

Maclin sounds like he's got my answer. If I only had the original Dynasty Manual that came with the boat, I wouldnt be asking you guys for help!!
 

Bondo

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Bondo, I am with you on that one.......It has been kind of hard for me to believe 300HP could come out of a Factory 1991 350. The problem was that I had 3 different people telling me different things at the shop. Owner says 260hp, his son (who works there as well) and the mechanic told me 300Hp.

Maclin sounds like he's got my answer. If I only had the original Dynasty Manual that came with the boat, I wouldnt be asking you guys for help!!

Ayuh,..... Boat manuals have a whole lotta Nothin' in 'em,.....
Legalize, 'n maybe which switch turns what on,.....

If ya can find one, yer Bible would be the 1991 OMC 350/ 5.7l Cobra Shop Manual,....
 

Ericmdoman

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JerryJerry05, I meant to say thanks for the numbers on the 4 series they produced that year. Did some more research and found that they did use '87 Model intakes on the 1991 boats such as mine. Being that my intake is stamped with 8-26-87, just confirms that I thought it was the original along with Maclin saying the same about his "high rise" intake. Thanks again
 

Maclin

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BTW My numbers were in a brochure, maybe a little optimistic, and definitely at the engine and not the prop.
 

bruceb58

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If ya can find one, yer Bible would be the 1991 OMC 350/ 5.7l Cobra Shop Manual,....
I have the OEM 1990 one that is floating around and everyone seems to have and there is no mention of HP in it.I was surprised.
 

Ericmdoman

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Jerry, I will make sure to do that when I get some time to pull the cover back off the boat. Bruce, same here, I ordered the original OEM 1991 Cobra Service Manual and like you, there is no mention of HP. Maclin, what kind of brochure? Was it part of the paperwork that originally came with the boat?
 

Maclin

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It was in what Volvo Penta called a Product Bulletin. I looked at it again and it had a footnote that the power ratings of 275hp crankshaft and 245hp prop shaft were from a model that had Volvo's Power Silencer thru-hull exhaust, so now I am not so sure about the 275 out thru the drive. But I bet it is close if not the same.
 

bruceb58

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Not sure if knowing the HP really matters. You will select the prop based on what WOT RPMs you achieve.
 

Tail_Gunner

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Take a stroll to the prop foum's it should be easy thing to do....50 mph with a 21 huh. Check your tach to be accurate across the enirte rpm band uuse gps for speed reading's...You valve covers how many bolt's hold them down or how many bots hold down the intake manifold makes a big differnece
 

Ericmdoman

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Maclin, I appreciate the info. Mine is the 800 series drive, Dog Clutch, with with the "thru hull" exhaust, not "thru hub". I am just settling on the the 260hp answer now...something just to go off of cause I cant find an exact answer anywhere and have always been curious. However, I am going to play with a couple props and check out the prop forums and see what works best. However, I was wondering, what size is your boat and what prop are you running? Speed and RPM?

BruceB and Tail Gunner, you are exactly right. I always wanted to simply know exact HP as it had been a debate between me and the family. However, Ill check prop forums, play around with a couple and find the right one...
 

Howard Sterndrive

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by itself, I wonder if any sort of intake change would yield any more HP on a boat engine. AT 4800 rpm, your stock manifold probably isn't causing any flow issues that need to be improved upon with a trick part.
I suspect intake manifold improvements yield noticeable results on a street/strip car where the 350 is going to turn high (6000+) rpms.
 
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