RPM question / suggestion

[Barney21]

Firstly I am with Guy and previous post regards put in neutral see what it will do.
Have a look at engine specs 2400 RPM sounds to me to be Max engine Torque, which is really where you want to be, maybe previous owner had found this out and propped accordingly???.
I dose of mechanical sympathy goes a long way.

[Jim Cate]

You are both right in that finding the unloaded max rpm would be a useful bit of info.

I'm not a betting person, but I'd be surprised if it failed that test... would wager a beer on it! HOpe the OP does the test soon and lets us know.

Jim

[sailorlink]

I repowered my sailboat in 2015, and the new Yanmar has a max rpm of 3200 instead of 3600. I have a variprop, basically the same idea as a maxprop. A diver adjusted the pitch for me, by means of a set screw that limits the prop travel to the required pitch as required by Yanmar. It worked well and didn't take very long, less that 30 minutes. So you would get a diver to decrease your pitch setting. After he does, you try it while still tied up to see the change in rpm, and he will go back down if further tweeks are needed.
Cheers!

[StuM]

Originally Posted by CaptJamesCook

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

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

According to SaildoatData, the Block Island 40 has a LWL of 27.5ft which gives a theoretical Hull Speed of 7.02 knots.

[CaptJamesCook]

Thanks everyone. I will check all and get back.

[thunderhoof]

You don't say what your boat is so we can't judge what hull speed should be. The 4hje is rated at 44 hp so I am guessing mid 40 ft overall making your hull speed in the 6 to 7 kt range. The numbers you give do not add up as others have said. Check boatspeed against GPS on a quiet day at open throttle.
I also had an engine rpm under load problem recently and after following up on all the good CF suggestions I had the injectors rebuilt and the engine runs smoother and stronger than ever. My engine had about 2K hours and the tip of the injectors looked really tired compared to the new ones.

[steve77]

Originally Posted by CaptJamesCook

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. idle was at 2.9 knots[/COLOR][/B]

Have you spoken with the surveyor about this? Surely he noticed something amiss. The surveyors I have dealt with have been very knowledgeable, and have been willing to provide opinions (verbally) about how a problem can be solved. Perhaps the surveyor ran the engine RPM up while in neutral and you have the answer by making a phone call.

Cheers!

Steve

[tinkrman69]

does it overheat at the 2400 rpms of full throttle? not always will it give black smoke with an over pitched prop, it could just b slightly over pitched. a lot of people go for slightly over pitching, so they have more low rpm power. it comes in handy when needing to stop the boat fast to avoid collisions. of course you won't need that with good piloting and helmsmanship.

wide open throttle -wot- and full throttle are two different things. the engine should be able to get up to wot and be held for a SHORT time @ 3200 or 3400 as per spec's but full throttle should be maintained around 2400 to 2600 for the long hauls. full throttle should be about 2/3 of WOT, the actual RPMs stated in the manufacturers specs, for WOT. I prefer to set my prop pitch to displasment/HP ratio in this range. As slightly over pitching puts more overall load on the engine.

the previous suggestions are all good and should be looked into. this is just one more tid-biit to help.....er....I hope it helps.

Good luck
Lance

[CaptJamesCook]

StuM Thank you.
I just talked to surveyor He suggested tach check and may it be a over pitch prop. Will have the tach checked. Then if needed check prop pitch. I have the Service manager checking his records on the condition of the injectors and date of inspection.

Thank you all
FYI 1992 Block Island 40 Yawl Sail Boat For Sale - www.yachtworld.com

[Cadence]

Originally Posted by tinkrman69

does it overheat at the 2400 rpms of full throttle? not always will it give black smoke with an over pitched prop, it could just b slightly over pitched. a lot of people go for slightly over pitching, so they have more low rpm power. it comes in handy when needing to stop the boat fast to avoid collisions. of course you won't need that with good piloting and helmsmanship.

wide open throttle -wot- and full throttle are two different things. the engine should be able to get up to wot and be held for a SHORT time @ 3200 or 3400 as per spec's but full throttle should be maintained around 2400 to 2600 for the long hauls. full throttle should be about 2/3 of WOT, the actual RPMs stated in the manufacturers specs, for WOT. I prefer to set my prop pitch to displasment/HP ratio in this range. As slightly over pitching puts more overall load on the engine.

the previous suggestions are all good and should be looked into. this is just one more tid-biit to help.....er....I hope it helps.

Good luck
Lance

Dogging an engine down by over pitching sure isn't doing the longevity any favors. Nor is continually running at the RPM it is rated at for HP.

[carlo de leo]

Well, I see its not a new thread, but the OP didnt said if the RPM rises in neutral, as some has asked for, and this essential.
I have exactly the same engine, same age and SAME "PROBLEM". And in neutral, my RPM doesnt get higher. its not a new issue to me. I already changed prop, filters and etc. And it doesnt bother me. But if the OP has had a veredict, It is very usefull to know.
tks!

[hpeer]

4JH4-TE. About 1,000 hours. I picked up some gunk/growth in the fuel.

1,600 forward/neutral/reverse.

Sent pump to rebuild shop. They found no problem problem but reported pump was “dirty.” Reinstalled pump, no further issues. Now about 2,000 hours.