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New engine rpm etc

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mtnrat

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"Well i have 16.5 hrs on the 3

"Well i have 16.5 hrs on the 350 I installed in my 1981 18 footer with a volvo 280 leg. I have an edelbrock performer with a rochester 4bbl
I have 2 props.
The first is a 14x19 and runs 30mph at 3000rpm with a WOT of 44mph at 4200rpm.
The second is a 14x23 and runs 34mph at 3000rpm with a WOT speed of 47mph at 3900rpm.
This was done at an elevation of 3000 feet and 80F. I only ran WOT for 30-45 secs max.
I think I should be getting more RPM and speed out of those props with such a little boat.
It seems as the speed increases the bow begins to plow a little. The boat has trim tabs but no trim on the leg.
How do I get more rpm?
Timing?
Trim? - Would mean a different upper on the leg I think.
Here is a pic of the boat and drive. I emailed the manufacturer and the weight including a SBC is about 2400lbs. I am sure I should be getting more out of this.
Thanks.
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"
 
"Try moving the trim pin one h

"Try moving the trim pin one hole away from the transom and towards the outdrive (there are three positions, select the second or third away from the transom)."
 
"I am already using the furthe

"I am already using the furthest out pin holes. On another note I checked the plug wires to make sure they were installed in the correct order and on the correct plugs. They were. I then checked the plug themselves and the were all ok except for #7. It may be too rich from not firing properly??? Here are some pics of the plugs in firing order 1-8-4-3-6-5-7-2.
Thanks.
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"
 
"Are you keeping the same gap

"Are you keeping the same gap in all spark plugs? Also, is the compression even in all cylinders?

Regarding the trim pin, you may have to try all three positions and see which one works best for you. If you have the trim pin in the farthest position away from the transom and the trim tabs are retracted (up) all the way, that's all you can do unless you put more weight towards the stern side of your boat."
 
"Same gap in all plugs. I have

"Same gap in all plugs. I have not done a compression test but will in the morn. Also I was just looking at the plug wires and all are orange volvo penta wire(could be the original ones), except #7 which is an unknown yellow wire. Could easily be the wire. I also think it is time for new wires. What would be a good type or brand to get? Here is a pic of the engine and you can see the plug wires, espesially the yellow one. The orange volvo penta wires look very old.
Thanks again.
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"
 
You may have a problem in cyl

You may have a problem in cyl #6 and #1. To me it seems to be lean. Is the intake manifold gaskets installed with the 'reduction' for the exhaust passage under the carb?
As for Your performance (plowing)'problem'. Take a 6ft straight aluminum or wood and put it from the transom and forward along the bottom. Is Your bottom concave? (gap between the bar and bottom?)
 
""Is the intake manifold g

""Is the intake manifold gaskets installed with the 'reduction' for the exhaust passage under the carb?"
Morten, what do you mean by this? Could I have installed the gaskets incorrectly?
As for the hull, I put a 4" box level from the transom forward and there is a definite gap. It is about 1/16" to 3/32". With a 6' straight edge it would be larger.
Thanks"
 
"The 'original' intake

"The 'original' intake manifolds has an exhaust passage between the stb and port cylinder row to balance off the exhaust pressure. Not sure about Your manifold, but it is probably one there too. 305 and 350 engines uses the same gaskets except for the restriction plate that in most aftermarket kits is not in the gasket but loose in the kit. Instead of the fully 1 1/2" x 1" open hole this is reduced to about 1/2" round hole by installing a metal 'plate' in the gasket. Check with Your intake manifold supplier which of the configurations to use. Too much exhaust means too much heat and the engine runs lean.
As for the bottom, the 'hook' is probably the reason for the nose dive and 'lack' of top speed. The rear part of the bottom acts like a huge trim tap lifting the stern pushing the bow down. The more speed the more lift. In severe cases it may even act like a vacum brake limmiting the speed to a certain level no matter how much engine You put into it. Run in 1ft choppy sea and it 'breakes loose' and the boat really takes off."
 
"They look nice!!!But perhaps

"They look nice!!!But perhaps should have been installed in the gaskets before assembly!!!
Yes, they are the ones."
 
"That is what I thought. I fig

"That is what I thought. I figured putting on an intake manifold was putting on an intake manifold. Done it many times, but always stock manifolds. Guess I will do that tomorrow. Tossed the papers that came with the manifold. Thought it was just propaganda, not something important!
Thankyou very much."
 
"Found the installation instuc

"Found the installation instuctions. No mention of installing the "reduction". I assume the reduction plates go over the centre holes on each side in the pic.
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"Just do a double check, but I

"Just do a double check, but I think I am right. Just install one on each side of the gasket and bend the tabs in the center holes to keep them in place during installation. You may have to get a new gasket kit, and use ATV silicone at the ends, not the rubber gaskets if delivered in the kits. They have a tendancy of leaking after some time."
 
"Those little metal plates go

"Those little metal plates go on the gaskets before installation. Not the little clips on one of the halves? They get mashed over (by you) as you place the plates on each side of the gasket. Trial fit them and you'll see what I mean.

On Chrysler small blocks, the gasket will leak exhaust out the intake like crazy if those plates are left out.

Jeff"
 
Ok I put in the reduction plat

Ok I put in the reduction plates in the manifold gaskets and I replaced the plug wires. Again the elevation was 3000 feet but the temp was warmer at 85F. Also the water was glass smooth.
14x21 prop 47.9 mph @ 4390 rpm.
14x23 prop 49.2 mph @ 4150 rpm.
That is a significant improvement. I have not played with the carb. It has the settings that I-5 automotive sent it with.
I think the max rpm for this engine (stock 1980 350) is in the 4400 to 4600 range. Correct me if I am wrong.
Maybe the next addition is vortec heads??
 
Yep still feels alittle nose h

Yep still feels alittle nose heavy. I ran with only about 5-10 gallons of gas. The tank is in the front. I wonder if I should get someone running along side to take a picture.
 
Honestly I think It will be a

Honestly I think It will be a better pay off getting the boat balance corrected and the hook in the bottom than trying to add engine power.
 
Good advice. I will be replaci

Good advice. I will be replacing the floor and stringers this winter. I am going to take care of the hook at that time. I checked the hook on one side of centre and a 4 foot level leaves a 1/2"+ gap. The trailer I have uses rollers and I think the spot pressure from trailering with the rollers has caused an uneven and hooked hull on the rear 1/3 of the boat. The 350 and volvo 280 leg have to be 1000lbs?
 
"I am going to make a good cra

"I am going to make a good cradle for the hull. And remove the engine and leg. I would not be surprised to see the stringers mashed in those areas, as the floor has a few soft spots the I drilled into and found wet rotten wood."
 
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