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Took the Ericson out for a full throttle one hour exercise run today

1911tex

Sustaining Member
Universal M25 5421. Temps constant between 185 degrees and 190 with 180 degree thermostat. GPS recorded 7.2 knots on windless morning, sans sails. Factory 2 blade prop. Original RPM gauge maxed at 2600 rpm??? Original alternator. Engine sound and speed with new bottom seemed like 3500 rpm. Engine idles at 600 rpm indicated and smooth up to 2600. Maybe need a new rpm gauge? No smoke, no sign of fuel out the exhaust.
 

GrandpaSteve

Sustaining Member
Mine idles at ~850, and max RPM is 3000. Max is governed, I think your tach is reading low. I think there is an adjustment switch in the back of the tach, but I don't remember for sure.
 

1911tex

Sustaining Member
Mine idles at ~850, and max RPM is 3000. Max is governed, I think your tach is reading low. I think there is an adjustment switch in the back of the tach, but I don't remember for sure.
Thanks! I will adjust idle up...easy to adjust on the engine. NOTE: The indicated idle @ 600 RPM is very smooth and sounds good; however, the tach may be incorrect showing 600 RPM? I need to find out about the behind tach adjustment switch before adjusting idle as it may make a difference on the indicated idle rpm. Hopefully someone will chime in on the "behind tach adjustment"?

I just checked the manual and the max rpm should be 3200 for this engine; however, there is nothing showing idle rpm:


I just did a google search and found this:

 
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Hagar2sail

Member III
Blogs Author
Get yourself. Phototach. They are cheep on amazon. We have an aftermarket alternator with the factory 2 blade. This is what our tach vs actual looks like:


Engine tach is top actual phototach reading below. Looks like we might be a bit over pitched.

1000
Rpm =1200

1500
Rpm=1740

2000
Rpm=2280

2100 - Full throttle
Rpm=2380
 

1911tex

Sustaining Member
Get yourself. Phototach. They are cheep on amazon. We have an aftermarket alternator with the factory 2 blade. This is what our tach vs actual looks like:


Engine tach is top actual phototach reading below. Looks like we might be a bit over pitched.

1000
Rpm =1200

1500
Rpm=1740

2000
Rpm=2280

2100 - Full throttle
Rpm=2380
Phototach ordered. Very interesting comparison indeed!!! Looks like my 600 RPM idle on the tach may actually be 800 RPM as GrandpaSteve stated above and my full throttle 2600 RPM indicated may actually be close to factory 3200 RPM, will find out soon! I think I may keep the original tach without adjustment and just interpolate ........Thank you!
 
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Kenneth K

1985 32-3, Puget Sound
Blogs Author
You can also compare your Tach rpm in idle vs in gear. My tach will reach 3000 rpm in idle at WOT, but only about 2800 in gear with boat moving at hull speed. I was only getting 2600 in gear two days ago until I swam below to chip all the barnacles off the prop. RPM in gear seems pretty sensitive to how clean the prop is as well as how clean the hull is.
 

supersailor

Contributing Partner
Our tachs are notorious for being inaccurate. Use a remote handheld tach to check for accuracy. The tach can be adjusted. The adjustment is usually on the back of the tach and is a screw that can be turned to change the reading.
 

1911tex

Sustaining Member
Received my digital tach from Amazon, ($24.39 delivered) ref. post above: Tach idle 600 rpm...digital 791; full throttle tach 2600+/-...digital 2877 rpm. Checking done at dock and neutral. Good enough for interpolation!! Underway the rpm may be a little different. Did not come with 9v battery.
Included nice case and enough silver tape for several years:
 

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Hagar2sail

Member III
Blogs Author
Received my digital tach from Amazon, ($24.39 delivered) ref. post above: Tach idle 600 rpm...digital 791; full throttle tach 2600+/-...digital 2877 rpm. Checking done at dock and neutral. Good enough for interpolation!! Underway the rpm may be a little different. Did not come with 9v battery.
Included nice case and enough silver tape for several years:
Excellent. So now you have some actual data. Yours is much closer to published than ours at full throttle. Was that under load?
 

1911tex

Sustaining Member
Excellent. So now you have some actual data. Yours is much closer to published than ours at full throttle. Was that under load?
No, at my slip (seems like that might be under some load?)...next time out will do another engine rpm check under way, I am sure it will be somewhat different.
 

Loren Beach

O34 - Portland, OR
Senior Moderator
Blogs Author
One small note about running in gear, at the slip. Without the increased flow of water past the hull you would get from being under way, the engine will not achieve max rpm's in gear. I have noticed this several times over the years. Not sure how significant the difference is, but at least 100 rpm, or a bit more.
 

1911tex

Sustaining Member
One small note about running in gear, at the slip. Without the increased flow of water past the hull you would get from being under way, the engine will not achieve max rpm's in gear. I have noticed this several times over the years. Not sure how significant the difference is, but at least 100 rpm, or a bit more.
Loren if that is the case, I should be able to indicate 3000 RPM at full throttle if only 2877 RPM at the slip! Good news!
 
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