new prop or is tach off

[newboatowner]

Good day to all of you shoveling out of the mess left by the last snow storm.
I am passing the winter thinking about upgrading my boat - a Catalina 30 with a Universal M18 engine. I have been on this site many times trying to get an idea of what I can do to confront the ageless problem of low engine performance and have had many suggestions from all of you.
The latest chapter is as follows: The boat in on hard and I removed the prop and took to a shop where they showed me that it was undersized. The specs call for a 13X10 and this one was a 12X7.
I have the opportunity to get a collapsible one (two blade) that is 14X10. The shop told me that it would work but that the RPMs would be reduced because of the size change. I remember that the RPMs at WOT engaged in forward was about 2100. I believe that it was about 2300 in neutral. (after adjusting the governor).
I do not know if the tack is accurate. I am afraid of backing off the adjustment screw for the governor any more. Are there any suggestions of how I can test the tach for accuracy? If it is accurate, why am I getting low RPMS?

 

[Ralph Johnstone]

Are there any suggestions of how I can test the tach for accuracy?

Hand held optical tachs are cheap enough that you could get a few of them and take an average. I would think you should get a reasonable figure (+/- 5% error at worst) with one of these. It's a start to see what you're dealing with between the engine and the mounted tach.

According to Gordon Torresen

http://forums.sbo.sailboatowners.com/showthread.php?t=8532

your engine has a max RPM of 3200 and a cruising RPM of about 80% or 2600 RPM.

The mounted tach may be a little .............