Can’t get max RPMs in gear

[freelandken]

Have a Perkins 4108 and Hurst trans. Went out about 2 weeks ago and everything seemed normal, but several days ago, when I attempted to reanchor, I realized the rpm’s wouldn’t go above 1500. 2200 is usually the max. Don’t know if it was consequential, but about a week ago I accidentally started the engine with full throttle. I immediately throttled back. So now I can get full rpm’s in neutral, but not in gear. Prop is not fouled in any way. There does seem to be a “different “ sound when put in gear now. Transmission fluid is good.
Any ideas about what could cause this or what to look for?
Thanks in advance for any input.
Ken

[skipperpete]

Hi Ken, here are some of the simplest reasons why your engine might not reach 2200 under load.
1. If you have an electric stop solenoid it might not be fully re setting to the run position.
2. Fuel problems... air intrusion on suction side, failed lift pump valves, clogged filters and water in filter bowls.
3. Tight propshaft... can you turn the shaft by hand?
4. Maybe a blocked exhaust... it does happen and will reduce power output.
If none of these issues are the problem, post a bit more info and The forum might come up with a better troubleshooting plan.

[mrcarson]

Change your fuel filter now. Incl the small (screen) one that's often in the fuel line going into the fuel pump inlet line.That's one of the primary causes of that problem.
THEN worry about other things. You've checked your shaft rotation and something on prop of course??.

[freelandken]

Prop was checked for any fouling and play. Prop spins freely in neutral. Checked for shaft play at trans also. Seemed solid. The noise coming from trans when put in gear concerns me. It was rebuilt only about 3 1/2 years ago.
Will check /replace fuel filter, as suggested by mrcarson. Could the fuel filter be the problem, although rpm’s are good in neutral?
Thank you both.

[mrcarson]

Filters are one of the first things. Starting to clog. Allow fuel flow for idling but Not the volume for open rail. Check your manual some older donk designs have a screen filter in Fuel pump line. even my 2010 D Max ute has a secondary filter in line. waaay away from main, under veh.
There are umpteen reasons causes. Progressive is the word. But no physical retardation. is often fuel related. Flow. timing. air ingress. filter. It is running "smoothly" on idle?. No missing or lumpiness.

[freelandken]

I am embarrassed to say that a cleaned bottom and prop has resolved the issue. Although there was nothing wrapped around the prop, there was enough growth to create the problem. The Lake Worth lagoon/ mooring area is a notoriously bad area for growth and I had actually been trying to get the bottom cleaned for months.
Thank you all for your input.
Ken

[skipperpete]

Originally Posted by freelandken

I am embarrassed to say that a cleaned bottom and prop has resolved the issue. Although there was nothing wrapped around the prop, there was enough growth to create the problem. The Lake Worth lagoon/ mooring area is a notoriously bad area for growth and I had actually been trying to get the bottom cleaned for months.

Thank you all for your input.

Ken

Hey thanks for the update on your loss of engine rpm under load, happy motoring.
Pete.

[mrcarson]

Glad you're fixed. Your first post said prop was not fouled. Most of us clean bottom/antifoul every 12/18 months.. I took it that using the boat. You did too.
I do. Plus drag bottom of keel over a particular sandbar in club channel on a rising tide to stop that whiskery moustache forming on bottom and round lower sides.
A long handled deck broom. with you in water (or dinghy). get most of the growth if done regularly to below the sun (growth) line too. Strapping an inflatable fender, (sized to suit) on brush or wide scraper end also applies extra pressure upwards. to help the scrubbing. If there is a diving club/divers. Locally. Most of them have persons willing to do a scrub for cash?.
SOME are better than others. Always.... Ask around your area first.
But. the best way of keeping her clean. Is to USE her regularly. Then some more.
Also check that you are using the right antifoul for your area and hull material.
Differing areas/Water consistencies require different brands/chemicals in them.
A High flow current. In HOT WATER Outlet channel for power station. (us). etc. We get up to 4.5knots with very high electrolosis and HOT water where we are. two tides a day 365 a yr.
Boat used regular. up to 12/15 months. Boat stays fairly clean (with occasional help).
Parked. growth there after 4 to 6 months. THICK by 12 months.
You live and learn don't you. Hey. Now USE it.