Engine will not reach max RPM |
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8122pbrainard
Grand Poobah Joined: September-14-2006 Location: Three Lakes Wi. Status: Offline Points: 41045 |
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Posted: August-07-2018 at 4:25pm |
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What is the advance your mechanic found or did he just tell you it was "OK"?? |
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samudj01
Gold Member Joined: March-10-2009 Location: NC Status: Offline Points: 972 |
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Sounds similar to our issue last summer.. I was convinced it was carb related...ended up being the distributor advance. Make sure the plates move freely and that the springs are still good. And of course, also check that the secondaries are opening. You may want to take a look at our thread "New to me 78 Tique"
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78 Ski Tique, 72 Skier w/302's, 93 SN w/351 & 17 GS22 w/zr409
Previous - 99 Sport Nautique w/GT40 and 87 Martinique w/351 |
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63 Skier
Grand Poobah Joined: October-06-2006 Location: Concord, NH Status: Offline Points: 4269 |
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I can see getting 110 since the engine wasn't rebuilt, but would not expect 110 across the board, more of a range than that. Just guessing but seems unlikely it would be that consistent. How many hours are on the engine? Anyway, I don't think compression is your problem so go ahead with the other suggestions.
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'63 American Skier - '98 Sport Nautique
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starbox189
Newbie Joined: April-06-2009 Location: United States Status: Offline Points: 27 |
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Mechanic said he checked compression and it was consistent at 110 psi. Wondering if he just assured me he did to appease me. Anyway, I think I'll check the carburator secondaries, fuel filter and fuel pump next.
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Bri892001
Grand Poobah Joined: September-27-2008 Location: Boston MA Status: Offline Points: 4947 |
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Agree with Mark.
Was also thinking to check that the throttle cable is allowing the carb to open up to full throttle. A lot of stuff on your top end was taken apart and put together. Throttle cable is an easy thing to pinch or potentially to connect wrong. |
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MACS81SN
Senior Member Joined: May-27-2009 Location: NW OH / S. MI Status: Offline Points: 109 |
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Verify secondaries on carb opening properly. 34-3600 is about where they start opening
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Mark
1999 -SN - 502 Python 1981 - SN Owned 33 years - Sold 1968 - Mustang - Sold |
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63 Skier
Grand Poobah Joined: October-06-2006 Location: Concord, NH Status: Offline Points: 4269 |
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So, same boat, prop, etc. and lost 800 rpm. My first comment would have been to check advance and total timing, sounds like you did that, when you say advance is OK you had a timing light that could read total timing?
If not timing then fuel, might want to get a pressure gauge on the fuel delivery to make sure the pump is putting out enough pressure post rebuild. Also look to see if secondaries are opening fully. |
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'63 American Skier - '98 Sport Nautique
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8122pbrainard
Grand Poobah Joined: September-14-2006 Location: Three Lakes Wi. Status: Offline Points: 41045 |
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The actual reading is not as important as the variance between cylinders. All cylinders should be within 5% for best performance or a max of 10%. Depending on performance level, stock engines run 130 to 200 psi new.
Didn't your mechanic run a compression test? |
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starbox189
Newbie Joined: April-06-2009 Location: United States Status: Offline Points: 27 |
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What should the compression be? Thanks.
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8122pbrainard
Grand Poobah Joined: September-14-2006 Location: Three Lakes Wi. Status: Offline Points: 41045 |
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Sounds like the water got in from the top end??? What readings did your mechanic get from a compression test after the repair?
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starbox189
Newbie Joined: April-06-2009 Location: United States Status: Offline Points: 27 |
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Hello All:
I have a 1981 Southwind with a PCM Ford 351. I recently had water in the engine oil and had new head gaskets installed, heads planed, new exhaust manifolds, new plugs plus other misc new parts. The oil was changed 5 times to clear out the water. The oil looks perfect now. The engine used to max out at around 4400 RPMS. Now it only gets to 3600 RPMs. Timing is 10-11 degrees BTDC at idle, timing, advance is okay, dwell is okay. It sounds great and runs smoothly but won't go past 3600. It has around 450 hrs. The marine mechanic who did the work is a very experienced and I have known him for years. He can't figure it out. Any thoughts?? |
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