rpm, cooling??? don't know

[captran]

I guess this is my summer for issues.  motorsailing along fine at 5 knots with jib.  put auto pilot on and go grab a chart- 2 minutes.  when I come out the auto is struggling to keep it's course.  and the rpm/and engine sounds different.  speed decreases and temp goes up to 168ish.  usually runs at 160, maybe 165 at higher temp.  slow down, check the strainer- looks good.  water still coming out but can't tell if it's less.  felt like I snagged a crab pot- kinda a drag on the whole speed.  pretty soon speed is 1 knot at 1300 rmp, where usually it would be close to 4.  long story short- get towed in (the tow guy released his tow rope under the boat while in gear and wrapped it.  after getting in, we're able to get his line off and I move the boat, but in the marina I'm going slow anyway.  but once tied up I run it at 1500 rpm for at least 15 minutes in gear and no heating/cooling issue- stayed at 160.  In the morning I plan on taking it out and running it for an hour and see if it behaves as it did today with lower speed and cooling.  any ideas on things to check?  I"ll check the coolant level, when it cools down.  oil and transmission levels OK.  really thought I'd snagged a trap.  could it have come off when the tow line wrapped up?  there was a lot of grass out in the bay, but the shaft when I got in the marina looked uncluttered.  seaweed maybe?  holy cow.

[Ken Juul]

Similar thing happened to me a couple weeks ago.  No overheating just a loss of speed and inability to reach max rpm.  I ran shifted to reverse for a bit and then back to forward and all was better.  I did not see anything in the water but something was on the prop.  The downside is if it was a line I could have made it worse by backing down....got lucky....didn't have to go swimming this time.

[captran]

That's sort of what it felt like, but I didn't put it in reverse.  if there was something there, I suspect it got dislodged when the tow guy wrapped his tow line around my prop, or in the tow in.  I just ran it for a half hour in the slip, starting at 1000 rpm, then 1250 and 1500, for 10 minutes each.  no cooling issue. then  took it out for an hour, running it at idle, 1250, 1500, 1750 and finally 2000 rpm.  for at least 10 minutes each, and it never went over 160 degrees.   so all together ran it over an hour and a half.  but to put my mind a little at ease, I'm having a mechanic out in a few minutes and will post any additional.  this board is so amazing, the experiences everyone has had and willing to share.  on that not, after  over three weeks there has still not been a reoccurrence of the fuel leak I reported in on earlier

[Ron Hill]

Randy : I'm sure you are correct that you snagged something and when you slowed/stopped for a tow whatever it was fell off.
I had a similar happening under sail where the wing caught a crabpot and wouldn't let go until we stopped. 

You didn't mention if you have a wing keel, but it sounds like it!!

[captran]

I do have the wing, but did stop and shut down while I checked the strainer.  had my visit with the mechanic.  he said flow is good, that if a bunch of eel grass impacted around the propeller it would not be efficient as it tried to motor, hence low speed and vibration and a slight rise in temp..  I should have put in in reverse as other commented.  anyway, he said if it ran fine for my 1 1/2 hr motor around this morning that it's no longer a suspect and whatever it was could have come off o the way in.  yay!!!  I guess despite the less than perfect weather, I'l go resume my retirement cruise!  and got lucky here in Anacortes and  the sail loft UK sails came and picked up my jib to restitch and will have it done by 10 am tomorrow.  just like sailing- some moments great and at other times no so much.   thanks all, fr your ideas.