Visit our Popular Forums

CaptJamesCook · 17-08-2017, 18:33

Yanmar. 4jhe with maxi prop
Full throttle I can only get 2400 RPM . It should be getting 3600 RPM
Oil pressure okay at 4.5 hg/Cm2 Temp.okay at 80C
Any suggestions?

**a64pilot** · 17-08-2017, 18:37

Reduce pitch, your overpropped.
I assume though that your close to hull speed? Cause other things like a clogged exhaust elbow can cause this too, but if your pushing the boat at hull speed at 2400, your overpropped

**Wotname** · 17-08-2017, 19:22

And if not at hull speed, clean bottom.

donradcliffe · 17-08-2017, 19:30

Replacing both fuel filters on a 4jh3 te got me from 2400 to 4000 rpm last week. Engine ran fine otherwise.

One clue that it is fuel starvation vs overpropping was there is no black smoke with fuel starvation.

model 10 · 17-08-2017, 19:35

Who would want 3600 rpm? Way too much noise. The pitch was probably set by some cruiser.

SSgtPitt · 17-08-2017, 19:40

Is your prop clean?

Captsteve53 · 17-08-2017, 22:52

FIRST THING

id you ever get full RPM? if not then all above would be correct!

If this is a new situation:

1) Is there black or other smoke at your max RPM?(if so probably over pitched/dirty prop etc
2) Replace all fuel filters
3) Can be a malfunctioning fuel lift pump
4) Could be a blocked pick up pipe from tank or lines
5) Partially blocked exhaust Riser
6) Malfunctioning Turbo (if fitted)
7) Partially Blocked air filter
8) Check engine adjustment on cables(getting full throttle)
9) Check actual RPM with laser or similar
10) Check engine is returning the correct amount of fuel to tank

Cheers Steve

steve77 · 18-08-2017, 01:03

Before everyone jumps to the prop, I would ask if you can reach full rpm in neutral? Also, were you ever able to reach full rpm but now something has changed? These questions will help get useful answers.

In my case it was the platinum plated Yanmar secondary filter that was the problem.

Cheers!

Steve

Steadman Uhlich · 18-08-2017, 05:12

Quote:

Originally Posted by steve77

Before everyone jumps to the prop,
I would ask if you can reach full rpm in neutral? Also, were you ever able to reach full rpm but now something has changed? These questions will help get useful answers.

In my case it was the platinum plated Yanmar secondary filter that was the problem.

Cheers!

Steve

As I recall, the boat is old, but new to you, as you just got the boat recently.

My friendly suggestions:

1. Knowing whether or if you have experienced a new problem, and whether you have reached higher RPMs with this boat's engine before, would be good for others to know in Troubleshooting. Or, is this a condition that "came with the boat?"

2. Check to see if you can reach higher RPMs while in neutral. Tell others here the result.

3. Be upfront and clearly descriptive about your history or experience with this engine. How long have you owned it? How much time have you had using it? How many previous hours on it? What has been its usage in recent year? Was it in long term storage while boat was on the hard or in storage or waiting to sell?

keepondancin · 18-08-2017, 05:35

Maybe you should check the accuracy of your tach using a strobe tach shot at the crackshaft pulley just to make sure.

CaptJamesCook · 18-08-2017, 10:08

I thought I was giving good info. but as steady pointed out I left some gaps... Thank you.

Quote:

1. Knowing whether or if you have experienced a new problem, and whether you have reached higher RPMs with this boat's engine before, would be good for others to know in Troubleshooting. Or, is this a condition that "came with the boat?"

Not new PO says that 2400 RPM has always been norm. But 4JHE Engine spec's say 3600 RPM

Quote:

2. Check to see if you can reach higher RPMs while in neutral. Tell others here the result.

I will next time I get to boat.

Quote:

3. Be upfront and clearly descriptive about your history or experience with this engine. How long have you owned it? How much time have you had using it? How many previous hours on it? What has been its usage in recent year? Was it in long term storage while boat was on the hard or in storage or waiting to sell?

This was during sea trail with surveyor. 2192 Hours on the engine average 87 hours a season.. Well maintained. Maine sailing season, professionally maintained by Marina crew, stored indoors since PO having it built in 1992. Commissioned every season no long term hard storage.

Hull is very clean. No Black smoke. It was noted that the throttle cable was stiff and probably needed lubed or replaced. Prop was clean. Not sure but I assume the filters were change at beginning of season. Not sure how many hours on them. I will check that.

Hull speed at 2400 was 6.6 knots
2000 was 6.3 knots
1550 was 5.1 knots
1150 was 3.6 knots
idle was at 2.9 knots

Cadence · 18-08-2017, 10:38

The suggestion of checking RPM in neutral is the best place to start.

Dave22q · 18-08-2017, 10:48

Quote:

Originally Posted by CaptJamesCook

I thought I was giving good info. but as steady pointed out I left some gaps... Thank you.

Not new PO says that 2400 RPM has always been norm. But 4JHE Engine spec's say 3600 RPM

I will next time I get to boat.

This was during sea trail with surveyor. 2192 Hours on the engine average 87 hours a season.. Well maintained. Maine sailing season, professionally maintained by Marina crew, stored indoors since PO having it built in 1992. Commissioned every season no long term hard storage.

Hull is very clean. No Black smoke. It was noted that the throttle cable was stiff and probably needed lubed or replaced. Prop was clean. Not sure but I assume the filters were change at beginning of season. Not sure how many hours on them. I will check that.

Hull speed at 2400 was 6.6 knots
2000 was 6.3 knots
1550 was 5.1 knots
1150 was 3.6 knots
idle was at 2.9 knots

My first impression is that something is very wrong with your numbers. Idle at 6-800 should not push your boat much over 1 kt. If you really idle at 2.9 kt, docking must get very interesting. You might check your instruments.
You might also see how many RPMs you get with the prop removed before you worry about pitch.