1999 Gulfstream with twin HPDI 200's on a factory Armstrong bracket.

[camandkel02]

I have a Gulfstream that had OX66 EFI twin 200's on an Armstrong bracket up until August of this year took a trip to Marathon Key and lost my port side engine.
Hole through the block! But not surprised for 21 year old engines! I am impressed how long they lived
So anyhow wanted to repower with four strokes but guess what no one has a single engine to sell.
I hate being off of the water so I found two 2003 HPDI 200's to get me through till the market fixes itself.
Got the engines mounted and set up and they run great but seem to struggle in the performance area.
I have 17 pitch props and the engines are mounted on the top hole on the engines and the bracket.
My OX66 EFI's were mounted in the same spot with 19 pitch props and performed great.
What am I doing wrong? I think I might have a mounting height issue but I don't know.
By the way with the engines trimmed all the way in no tabs there is a huge rooster tail coming from the sides of the engines that I did not have before with the OX66s.

Any help would be greatly appreciated and I apologize if I'm not doing this right I have never posted in a forum before..

 

[VeroWing]

Well if engines themselves are good runners and roughly equal to engines replaced, then your change from 19s to 17s will take away from your top end but should give you a better shot out of the hole and mid-range. A rough rule of thumb regarding outboard height is: cavitation plate over prop should be 1" higher than hull bottom directly in front of it for every 1 foot back from transom. So if your bracket sets outboards back 3 feet then your transom then cavitation plate would be 3 inches higher than hull bottom in front of them. You'll need a long straightedge and a helper to get it right. Be sure cavitation plate is parallel with hull bottom. Again, this is a rough "rule of thumb" point.

 

[camandkel02]

Thank you for your fast reply!
My bracket sets back 30" from the transom. I have a V in the dead rear of the transom so do I place the straight edge on the cavitation plate inboard of one of the twin engines or outboard? Seems like with the V there is about 1 1/2 inches difference between those two measurements. So two and one half inches above with the 30" bracket. Also for the purpose of the measurement do I tuck the engines all the way in or trim out to make the cavitation plate level with the bottom of the hull?
Again I appreciate all the help I am really lost with this but want to do it right. Planning on returning to the keys for Thanksgiving for some fall offshore fishing.

 

[wrxhoon]

From what you describe your engines are mounted too low .

Do you know the gear ratio on the OX66 and the HPDI? Are they both 1.86? If yes they should perform about the same with the same props. What RPM do you get at WOT with the DPDIs? What did you get with the OX66?
Do you know how healthy they are? Going from 19" pitch to 17" should increase the RPM at WOT and get on the plane quicker if the engines are at the correct height.

 

[camandkel02]

Sorry for the time gap. Took a little while to raise and test.
You are correct they were way low. 4" low. Not enough actual information in "fact" on the internet but a lot of opinion about engine height. Here is what I did so the information may help someone else.
Had to raise the engines to the top hole on the bracket and the lowest hole on the engine to get it right. Its perfect now.

1999 Gulfstream
Full Hardtop
Twin 2004 HPDI 200's
30" Armstrong flat bottom bracket (Factory)?
Main tank Full
Aux Tank 1/4
Oil Tanks Full
Water tank Full
No Gear no ice
4 passenger's totaling 700 lbs
Sea conditions were 1 to 2 6 sec Wind 10Knts NE Traveling N
My Numbers are

WOT#s Cruise #s
rpms 5700 3900
mph 53 35
37.9 GPH 15.5

Does this per standards seem appropriate ? Good? Bad? Want to do the best I can with what I have.
I would like to know what the performance numbers on this same setup are for F200s.
Doesn't seem like GW has any performance numbers on the Gulfstream with 200 HPDIs either
If the do I cant find it. I appreciate all the advice I can get.

 

[camandkel02]

Sorry forgot to add these Numbers are with the 19p SWS stainless props.

 

[magicalbill]

My 2007 Gulfstream had F200 (6 cyl) and my numbers were a somewhat lower than yours, but I had bottom paint. Not sure of the props, but they were the standard issue wheels that Grady put on the F200's for the Gulfstream. I have no clue what hole they were mounted either. They ran great so I never looked or cared

3800 RPM 30MPH Mid-Cruise. 2.0 MPG
4100 RPM 33MPH Mid-Hi Cruise. 1.8-1.9 MPG
4400RPM 36MPH Hi Cruise 1.7MPG.

I have read that the HPDI's were the perfect power for the Gulfstream hull. After viewing your stats, I would agree, although my F200's were marvelous. Not a peep out of them in 1100+ hrs, except for the "exhaust corrosion problem" that enveloped my engines as well as all the 225's.

I

 

[camandkel02]

@bill
I guess it doesn't make a difference if you don't have the boat anymore but I can tell you i raised 3 inches and made the performance increase alot. I can't go any higher but if I could I would try it.

Our numbers are close and it makes me want to do an exact rpm comparison.
Seems like the extra weight of the 4S's on yours. you should have been higher than me. Right now at WOT my antiventalation plates seem to be perfect front side slightly in the water most aft 4 inches right on top of the water.
Me 3900 rpm 35 mph 2.25mpg
You 3800 rpm 30 mph 2.0mpg

I realize there is a 100rpm delta between us but still shocking for 2 strokes v/s 4's.

 

[magicalbill]

camandke102:

My son now owns the boat; I see it all the time. (You can view it in this months issue of Anchorline, Grady's quarterly Newsletter. I write for Grady on occasion, and they featured my story about moving to Michigan and taking our boats with us. Anyway, you can view both the Gulfstream and my current Marlin if you want.)

I have always heard that those HPDI's were the Hot Ticket for Yamaha, although I do think you have extra-special stats. I would put a fence around the boat and allow no one near it to make sure nothing changes. Your rig is rockin'.

These days my son removed the bottom paint, (lousy and lengthy job) and his numbers went up a bit- he's now at 2.0-2.1, sometimes 2.2 on a flat day. I can't remember his cruise numbers, but they went up a tad as well, although not to yours.

If he offloaded all the ancillary gear and 200 lbs of toys for the kids and judiciously removed every unnecessary bit of weight, he may be approaching your stats, I don't know. I do know he's not gonna experiment with engine height..his life is too much of a Whirlwind as it is to justify the extra time, and the boat is running well.

I assume your travelling light as well? How many folks on board when you clock those numbers? Congrats-that's astounding.

 

[DogBone]

I have a 1993 Gulfstream with 2006 175 hp HPDIs and from memory I get 30 mph at 3900 RPM, around 2.2 mpg under good conditions and moderately loaded boat. Tops out at 48 mph and 5900 RPM. I'll go and double check my props and see what height the motors are mounted. The OP numbers are impressive.

 

[camandkel02]

I have a 1993 Gulfstream with 2006 175 hp HPDIs and from memory I get 30 mph at 3900 RPM, around 2.2 mpg under good conditions and moderately loaded boat. Tops out at 48 mph and 5900 RPM. I'll go and double check my props and see what height the motors are mounted. The OP numbers are impressive.

camandke102:

My son now owns the boat; I see it all the time. (You can view it in this months issue of Anchorline, Grady's quarterly Newsletter. I write for Grady on occasion, and they featured my story about moving to Michigan and taking our boats with us. Anyway, you can view both the Gulfstream and my current Marlin if you want.)

I have always heard that those HPDI's were the Hot Ticket for Yamaha, although I do think you have extra-special stats. I would put a fence around the boat and allow no one near it to make sure nothing changes. Your rig is rockin'.

These days my son removed the bottom paint, (lousy and lengthy job) and his numbers went up a bit- he's now at 2.0-2.1, sometimes 2.2 on a flat day. I can't remember his cruise numbers, but they went up a tad as well, although not to yours.

If he offloaded all the ancillary gear and 200 lbs of toys for the kids and judiciously removed every unnecessary bit of weight, he may be approaching your stats, I don't know. I do know he's not gonna experiment with engine height..his life is too much of a Whirlwind as it is to justify the extra time, and the boat is running well.

I assume your travelling light as well? How many folks on board when you clock those numbers? Congrats-that's astounding.

1999 Gulfstream
Full Hardtop
Twin 2004 HPDI 200's
30" Armstrong flat bottom bracket (Factory)?
Main tank Full
Aux Tank 1/4
Oil Tanks Full
Water tank Full
No Gear no ice
4 passenger's totaling 700 lbs
Sea conditions were 1 to 2 6 sec Wind 10Knts NE Traveling N

 

[camandkel02]

7

 

[camandkel02]

HOPE'S too low

 

[camandkel02]

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Set at 3" above the bottom of the boat with 30" of backset from transom