26' sea Ray Merc 260 max RPM 2900

72GT160

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Apr 22, 2007
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I have a 1985 Sea Ray 260 Sundancer.
5.7 260 few hours on new rebuild.
New distributor, set 8* btdc
Rochester carb just rebuilt.
New fuel pump
New gimble housing
New upper, lower drive 1:47 ratio
16" ,19 pitch prop
Not water logged.

Runs beautifully, just won't go over 2900 RPM and 21 mph...

Need some help figuring this one out.
 
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tpenfield

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Was that prop on the boat before all of the engine work, and was it getting to the proper RPM?

The prop seems really big to me, particularly for that boat and engine match up. I agree with Bt Doc . . . 14" diameter would be something to try.
 

achris

More fish than mountain goat
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My personal preference would be to stay with the larger diameter (15"/16"), but continue with the suggestions above, reduce the pitch to maybe 17, 15 or even 13".
 

72GT160

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Yeah this prop was in the boat when bought so, just tried it out. I'll see if I can try a few different combinations of props and go from there. Thanks.
 

Ryan50

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I have an 87 Sea Ray 250 with same engine and carb. 15x17 prop=4800 rpms and 39 mph.
 

Bondo

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New upper, lower drive 1:47 ratio

Ayuh,..... Shoulda bought a 1.65:1 ratio,....

GM HEI distributors, Ain't marine rated either,.....

Is this a new to you project,..??
 

72GT160

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Sorry, not an HEI. Not a points dist. Is what I meant. Why should I have bought a 1:65??? A 1:50 was stock but, you can't get that anymore so, 1:47.
 

achris

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Yes, you can get a 1.62:1, and the reason is because using a high reduction allows you to use a larger pitch prop, getting you back in the right propeller size range. Also, the larger the pitch, the more efficient the prop...

Chris......
 

kbsunlovers

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Jun 10, 2012
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+2 on waaay too much pitch. '85 250DA with a very mild 383. 1.47:1 SEI. 16x16 Aluminum "elephant ear" 3-blade (Michigan). Pulls like a freight train right up to 5K if I really wanted to. Edelbrock 1409 & Performer air gap.
 

72GT160

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Well, I got a new prop. 16x14. Got over my 2900rpm issue. Then I got to 3500rpm and would backfire through carb. Checked timing, still at 8*BTDC. Replaced coil wire as that is only old piece in ign. Still popping. Found carb secondary upper shutters not opening due to a linkage issue. Pulls great now! Till a little over 4000rpm and pops again. So, went and got a fuel pressure gauge and installed at fuel filter at other exit point in mount. No pressure at all. Think there is air in there, have to re-install and got from there I guess.

Think prop is small tho, going to go up to 16 I think.
 

Bondo

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So, went and got a fuel pressure gauge and installed at fuel filter at other exit point in mount. No pressure at all. Think there is air in there, have to re-install and got from there I guess.

Think prop is small tho, going to go up to 16 I think.

Ayuh,..... Before ya change the prop, get the lack of fuel issue sorted out,....

Then make sure it'll pull 4600/ 4800 rpms at Wot,.....
 

72GT160

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Yeah I'm not changing prop till I figure out fuel issue.

So, here's where I'm at. I got gauge installed between carb and filter, inline. No pressure. None. But, seems to run fine sounds good on muffs. I have a secondary sediment clear filter inline before main filter to see what's coming out of tank. I see it's not full and see fuel trickle into it when running. Thought, fuel tank venting issue so, it took fuel cap off. That's not it. After fiddling around with all the fuel lines I found a leak, tightened. Thought maybe there was air coming through fuel line fittings somehow, put some new hose claims on, not it. While it was running I pumped the primer ball, NOW I got pressure! Pumped up to about 3psi and motor started to bog down at idle, mixture issue I'm sure, I'm sticking with supply before dealing with that issue. After a minute or so, pressure drops. Pump up again and same issue, pressure drop to about 1/2psi. I know I should be getting about 4-6psi so, what gives? Fuel pump right? Well that's brand new. After talking to a racer buddy he said that the push rod for the fuel pump could be too short but just enough to push a bit to run.

So, question is, are there different part numbers for these fuel pump push rods???
Does anyone know what the measurement should be?
 
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72GT160

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FWIW, I just checked parts diagram and it's flat lifters, NOT roller.
 

achris

More fish than mountain goat
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Don't know the measurement, but the same part number (and therefore the same part) has been used since 1963, up to the last of the mechanical pumps, 1997...
Was your new pump genuine? Been quite a few non-genuine pumps on these forums that are brand new wrong.... One member went through 3 non-genuine before buying genuine and all his problems went away....

Chris......
 

72GT160

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Apr 22, 2007
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Hmmm, going to try to pull off today and see if I find anything visually. Not sure about genuine OE. Don't remember. I'll post what I find.
 
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