Low RPM in gear

[pjcomeau]

I've done too many changes at a time since I first bought my boat and I don't have a good baseline.

Last year my Kiwi prop failed and caused major vibration, prior year I had to replace my transmission (now have a Hurth 100 or new equivalent).

Like I said I've never had a baseline I really liked. So this year I decided I would try to get such a basline before getting another feathering prop (or getting my Kiwi fixed). A friend had a fixed 3 blade 15x9 that was used on a C34 with M25.

So at this point I have M25XP/Hurth ZF10 (equiv too HBF100)/fixed 3 blade 15x9.

So I don't have vibration issues, but I cannot seem to get the expected speed. At full throttle under way I cannot get above 2500-2600 (around 6 knots when no wind), but as the engine warms up I max out around 2200 (around 5.4 knots).

Not in gear I can go above 3000.

Everybody around the club, says I'm over pitched. but according to this site most of the fixed 3 blades in use are 15x10 with M25xp and 15x9 with M25 (which is where I got mine from).

I had the Racor filter and primary filter replaced. I think it was eventually "bled" properly, since it now always works just not very strong.

The Racor is before pump (should I still look at screen/filter at bottom)? I saw mention of intake screen; where is that (the boat came with new fuel tank).

Others mentioned not enough air, but everything looks like original setup. There is nothing in the air intake but a simple screen which is clear.

I know the injectors need cleaning (probably has never been done), could this be most of my problems?

What else can I check?

So to recap: So I always start under load with a max of around 2500-2600 (full throttle sometimes goes to 6 knots) and not too long after running I start to loose power and settles around 2200 (full throttle around 5.4 knots).

-PC

[Stu Jackson]

Our M25 has a 15x10 fixed.  Our engine goes to 3000 WOT out of gear and in gear.  We cruise at between 2450 and 2600, 6+ knots.  Anything over that is either an emergency maneuver, "blowing out the carbon," or just for fun seeing how fast we can go to check the condition of the bottom or the latest check on how well our quarterly diver did his work!    2650 engine hours.

It could be your tach is not calibrated, or that if your throttle wanders back to 2200 you simply need to tighten the friction screw inside the binnacle underneath the compass.

The intake screen is inside the fuel tank at the end of the fuel pickup hose.

Couldn't hurt to check the filter at the bottom of the pump.

[ozzie]

A couple of things to check is that the prop is not fouled with growth or rope? Also is the bottom of the boat clean?

Dave.

[patrice]

you simply need to tighten the friction screw inside the binnacle underneath the compass.

Hi,
In my case, the speed lever don't stay in place when I put it over around 1800 rpm.
I have to hold it in place.  And is kind of hard to push past this speed.
Could it be this adjustment under compass you are refering to ?
I was look at engine side, and no adjustment possible there.

thanks.

[Stu Jackson]

you simply need to tighten the friction screw inside the binnacle underneath the compass.

Hi,
In my case, the speed lever don't stay in place when I put it over around 1800 rpm.
I have to hold it in place.  And is kind of hard to push past this speed.
Could it be this adjustment under compass you are refering to ?
I was look at engine side, and no adjustment possible there.

Yes, that's it.  You can check it in our C34 Tech Manuals in the wiki, or www.edsonmarine.com

It's a pretty simple thing to adjust.

[RV61]

I had a similar issue when I first got my 1986 and could not get her to go 6 knots at full throttle.  And as Stu pointed "The intake screen is inside the fuel tank at the end of the fuel pickup hose." I simply pulled the pulled the pick up hose and removed the sreen which was fouled from growth and causing the fuel starvation. Since then she has run great. I also stared using Cetone booster ans it seems smoother and less vibration. Now on flat  lake 6.2 - 6.5 cruising and 7.2 full throttle.

[patrice]

you simply need to tighten the friction screw inside the binnacle underneath the compass.

Hi,
In my case, the speed lever don't stay in place when I put it over around 1800 rpm.
I have to hold it in place.  And is kind of hard to push past this speed.
Could it be this adjustment under compass you are refering to ?
I was look at engine side, and no adjustment possible there.

Yes, that's it.  You can check it in our C34 Tech Manuals in the wiki, or www.edsonmarine.com

It's a pretty simple thing to adjust.

oK thanks, will look at it.

[Joe Holmes]

I had the 25xp engine and 15x9 fixed prop, repitched it to 15x10.  Able to cruise as per Stu's comments.  I am located at RYC in Rothesay if you wanted to check out any possible differences.  Had the work done at Prop Doc locally. 

[pjcomeau]

I will check on what has been said to look at. Just to clarify, when I talk about loosing power with time, it happens with me holding the throttle to the max or close to it.

The boat has only been in the water for 6 weeks or so and therefore a very clean bottom. I might have to double check that the prop did not get fouled since being put in the water.

Joe, I assumed I would look at repitching my prop to 15x10 once I felt comfortable that everything was looking good (I knew about Prop Doc).
I decided to keep the prop as is (i.e. 15x9). Make sure that everything was good. No vibration (everything lined up and balanced), full power, expected speeds (i.e. above 6 knots at full throttle). The boat feels much better under power now, just that it is still pretty slow, I only get cruising speeds of 5.4/5.5 (and does not speed up with full throttle).

What difference/experience should be expected with 15x9 then moving over to 15x10. I'm assuming one thing is higher RPM for 15x9 to get same speed.

Joe, Do you have a 34? I did not know there was another 34 at RYC since Dan Phinney sold his. I knew there were a couple 36's though. I'm at RKYC and the other 34 here is 2 years older with an M25 and he motors past me with a 2 bladed folding prop.

Thanks

[Terry Forshier]

I had a similar issue and tried everything you have. Finally i had an old timer come to check the engine. He found the accellerator (throttle)  cable was not correctly set. that is it never opened the diesel line enough to get full power. It caused the same symptoms you are expweriencing. He just reset the little stopper higher up on the cable and "like magic" I had power and problem was solved. Worth a look at.

[Joe Holmes]

PJ- I am the only 34 (1988) at RYC at this time- bought it in 2010.  I picked up at least half a knot, can cruise at 6.2/6.3 at 2600 rpm with the change.  Prior to that there was a 2 blade fixed, 15x9 installed, but the previous owner had left the 3 blade on board.  Got tired of not keeping up while going up river and installed the re-pitched 3-blade, based on the information on this site.  Sounds like a fuel delivery problem.  I pulled the screen on my intake hose in the tank this spring before launch, and steamed out the tank.  That might be your issue.  It is not a difficult job, just a PITA.  I also adjusted my throttle cable with the installation of new throttle handle.

[Ron Hill]

Pierre : As A starter - your prop is NOT overpitched if you have the original 3 bladed Sailor 15X9 prop.  If a PO put on a 15X9 Michigan Wheel then you've got the wrong prop!  

Seldom is the lack of power in-gear problem caused by lack of air, it's usually the lack of fuel or overload from the wrong prop.  
As mentioned start with the fuel pickup tube and if that screen is still there remove the screen.  
Next change out the injectors.  
As a last resort you may have to have the injection pump rebuilt.

Just a few thoughts and ideas.  Hope this helps

[prh77]

One other thing to look at is the fuel tank vent. Next time she starts to bog down to 2200, loosen the fuel cap. If you regain RPM...bingo. Just one more thought.Also, as was mentioned, check the tach calibration. Mine was way off.

[pjcomeau]

I spent Saturday trying a few of the suggestions. The tank is new and the fuel pickup did not have a screen (and everything looked clean). I also checked the filter in the lift pump (which is placed after the RACOR filter) and it was clean. I checked the new RACOR filter to see if still clean (only replaced 3 or 4 weeks ago) and it was clean. I filled it up with injecter cleaner before putting it pack (suggested on site by a few people). Bled the air out.

After all that, I was back to square one. It starts very well. When first going I max out around 2600 on tach and get around 6knots (also no smoke, can't push it to smoke). Then I cruise for a while and very soon after it slows/maxes out to around 2200 and stays there (max speed 5.5 5.7). There is still room on the throttle (i.e. I can bring it back some and still keep it at 2200).

So I max out around "cruising speed" with no smoke and nice sounding. So not the end of the world.

I guess I'll have to get injectors cleaned (after haul out in fall) and try again next year. There are a few people mentioning that the "governor" has to be adjusted in rare cases. Maybe I'm one of them. I just don't know what else to try...

[mainesail]

Start with the simple stuff...

Have tachometer checked (need a digital photo tach)
Check that the fuel arm is moving the full range to WOT at the engine
Check that the alternator belt is not slipping
Check fuel system
Check exhaust elbow (could be plugging especially if the boat was ever over propped)