1986 268 weekender engine speed and planning?

I need to start writing stuff down...lol Anyway i installed a fuel flow gauge at 5 to 7 mph i'm using just over 3 gallons per hour 8 to 28 mph i'm sucking up 12 to 15.7 gallons per hour.I did notice tonight that once the boat hits 13 mph and i start to trim up the outdrive she seems to get on plane alot quicker
 
found it on craig's list. I just couldn't justify spending 500 for a prop that may or may not have helped
 
Sounds like things are improving, great news. I had a 1979 26 weekender with the 350 so should be pretty close to what you have as far as weight etc. I have been watching this thread and you have recieved some good ideas for fixes. Now, I'm going to ask what may be a dumb question but will ask it anyways in the spirit of helping. Have you double checked all your bidge pumps, as I recall at one time when I first got the 26 I was unaware of the manual/ auto bildge pump located under the steps going into the cabin and had been hauling water around for several weeks before I realized it was there. Seems the pump was not working in auto mode but would work in manual when I hit the switch located on the dash. I'm sure you have already checked but had to ask anyways. Good luck!
 
my pump that is located there is on a manual switch.But that area is always dry. For some odd reason the bathroom floor drain drains into that compartment
 
Sorrento 25,
If you want a used Mirage Plus prop, I have a 17 in. It was a little too much pitch for a 5.7L. I needed a 15 in like Lime4x4 found. You won't be able to use that with your 7.4L. And, it depends on the gear ratio in your outdrive. If you have a 1.50 or thereabouts ratio, it may be good. If you have a 2.0:1 you'll need more pitch. What kind of prop are you running now?

I found the Mirage Plus to be a greate prop. It has big blades, which is what you will want. I replaced a 17" aluminum with a 17" Mirage and lost about 600 rpm because of the prop design. It's a great prop model. I think list is about $600, I paid just over $500 and would sell it for $250, if you pay the shipping from New York. Excellent condition.
Cap10Pat@Verizon.net
 
i have 84 26ft sea ray same power plant same problem,how many peaple on board,?If its 2 adults mine does great, planes at 3500 plus i do have lots of bottom paint , but its coming off this spring,,mine rides great at 4000 , but planes earlier with the alpha 1 15X17 ,, if i take 4 full size adults three tenagers it dont come up, i tell some of the adults to get into the cabin while i attemt to plane off , good luck, boats best with a 7.4 bravo
 
tollycraft said:
I had a 1979 26 weekender with the 350 so should be pretty close to what you have as far as weight etc. I have been watching this thread and you have recieved some good ideas for fixes.
Click to expand...

My 1979 26 SR would do 21 MPH at 3000 rpms with a 260HP 350 Merc. This boat should do something similar.
 
Nice boat SB1. Bang on re: the 1979 26 ft. Mine would do about the same speed at 2100 rpm and stayed on plane at about that speed. I had a step down pump I was not aware of untill the carpet in the cabin got wet (first boat had a lot to learn) and after I figured THAT OUT no problem with getting up on plane fairly quickly. By the way, I love the 1988 30 ft EC I bought this year, twin 5.7s Mercruisers. You were right re: a post qiute some time ago that the boat handles very well a low speeds. Very stable on the water. Got caught in a pretty severe storm once this year and that boat handled great, nothing like confidence in your ship when something like that happens. Had a little trouble parking her at the dock in the high winds as I never had to do that with those type of winds before but managed, good experience though, as that was bound to happen sooner or later.
 
The EC handles lots better than the stern drive 30s. You will dock it with your eye's closed once you build up your hours.
 
I would look at trim tabs, then check your outdrive and make sure it is in proper down position. As long as the hull is clean,
the engine is tuned, the tabs work and the drive is adjusted down properly, that baby should be on a plane 2500 to 2800
rpm's depending on weight distribution. Also like someone else
mentioned check your tach. what kind of fuel consumption do you have. No way can you keep operating at 4000 rpm. I cruise
with my sundancer on a plane at 2800rpm
 
well after thinking about this problem for awhile i decided to do a compression check found 100 to 125 psi in all cylinders.That didn't sound right since the block was new and the heads were redone 2 years ago.I removed the valve covers and got the casting numbers off the heads. turns out the heads are 74 cc chamber heads which were used in 160 to 180 hp engines..Pulled the engine this weekend and replaced the cylinder heads with 62 cc heads.Hooked a battery up to the starter and redid a compression test now my compression is 165 to 170 which is alot better.Got the engine back into the boat sunday morning but the weather didn't want to go along with my plans. So i will have to wait to water test and c what kind of results i get now. I'm thinking it should improve. With the mismatch of parts i had going on i'm real sure it was never making any where near the 260 hp it should've been.
 
Will i decided to just install a new 350 vortec engine.Wow what a difference in power. The boat will come up on plane in 14 seconds now. I can keep her cleaning on plane around 3500 rpms.Now i just have to find a good prop for her.Current prop is 15.75 X 15 ss mirage 3 blade. Wot are at 4100. Gonna try dropping to a 13 pitch
 
Cap10Pat said:
At 27 mph you're not starting to come off plane by cutting 200 rpms. Maybe the bow coming up means the boat is returning to its intended angle. Maybe the angle of your outdrive and your use of tabs is pushing the bow down - which may also be slowing your speed. Try reducing your tabs,.
Click to expand...

That's the first thing I thought. You are thinking of "on plane" as the boat running level. That isn't the case with a lot of cruisers, they just run with the bow higher than smaller boats do. I have never run with my tabs down to adjust running angle, just list. I would think that you should be able to run with your drive trimmed all the way down all the time and tabs level. Trim tabs rob a lot of speed when you run with them down. My boat maintains "plane" at about 19 mph, maybe a little less if it's light. Yours should be similar.
 
lime4x4 said:
Will i decided to just install a new 350 vortec engine.Wow what a difference in power. The boat will come up on plane in 14 seconds now. I can keep her cleaning on plane around 3500 rpms.Now i just have to find a good prop for her.Current prop is 15.75 X 15 ss mirage 3 blade. Wot are at 4100. Gonna try dropping to a 13 pitch
Click to expand...

Why drop to a 13? Sounds like you have about the right numbers now.
 
mine will stay on plane around 21 mph. The reason i'm looking into a lower pitch prop is cause the wot should be around 4600
 
lime4x4 said:
mine will stay on plane around 21 mph. The reason i'm looking into a lower pitch prop is cause the wot should be around 4600
Click to expand...

Gotchya, makes sense. I thought the WOT should be lower, about where it is. You did mention it was a new engine though, they have a higher WOT some times. Mine are 4100.
 
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