Thanks Edb for your detailed response.

I will remove the bell crank lever from the shut off solenoid ASAP and hopefully this will be a quick fix for my lack of revs.

Unfortunately any plaques on the engine with arrangement numbers has long gone and I considered myself lucky to find the engine number at all.


The vessel was built in 1985 but I believe the engine dates from the 1970's so whether it was old stock or repurposed I will never know but I believe it to be the original engine. I am hoping the engine, gearbox, propeller were correctly matched at the time. The vessel weighs 27 tons with a water line length of 44 feet. This should give me a hull speed of around 8.5 knots which I can achieve at my current max 1500 rpm. According to an online prop calculator I need only 130 hp to reach hull speed which sounds about right. As the engine sounds great at 1500 rpm, blows no smoke and doesnt seem unduly loaded I am quietly confident that the motor is not lugging and with your guidance on the bell crank lever removal all will be remedied in the near future.

Ultimately I tend only to chug around and it is unlikely that I will be re pitching the propeller, the engine prop combo has been good for nearly 40 years and only let down by pitted liners!

I removed the throttle cable to see if the cable was restricting the governor travel but found it made no difference, that would have been a nice easy solution.

Again many thanks to you and Old Magnet, seems the actual horsepower shall remain a mystery but I'm happy with that. At the end of the day 8.5 Knots is plenty fast enough for me it was just annoying after 4 months of working upside down in a boat that I couldn't get full revs. I will update after removing the solenoid lever.

Hi waltini,
if your calculated hull speed is 8.5 knots and 8.5 knots is what you are currently traveling at with 1500 engine RPM then to me it would appear that all is as was originally designed as the prop etc. seems to be matched for these figures.
1500 RPM should make the unit economical.

An actual measurement of the current rack setting and a check in a current Rack Setting Book for your engine would tell us what HP the engine is capable of at the current 1500 RPM.

It could be that the engine is capable of more HP than your vessel requires to travel at 8.5 knots which tells us that the entire drive train has been set up correctly in the first instance--I stand to be corrected.

If the vessel and engine have lasted all this time without undue stress whilst traveling at its designed speed then I would leave well alone--as I said earlier our model trials at the Cat School showed there is nothing to be gained adding more HP to a vessel already traveling at its optimum hull speed except increased fuel consumption and decreased engine and drive train life.

Prop design is a smoke and mirrors scientific field all of its own we were told, and so we did little except to use 12 volt electric motor powered model boats with varying hull shapes and interchangeable pitched diameter and number of bladed props to see the effect of over pitching or under pitching the prop had on engine RPM and amperage draw(load) to tell us what the end net result was. This gave us a view into the murky world of prop design.
Somehow I have ended up with a prop slide rule calculator for props but have no idea how to use it.

The scan below shows the High Idle adjustment screw--if you wish to try and screw the screw out one half a turn to increase the engine RPM as an experiment and see what happens in regards to your hull speed and engine emitting black smoke (wasted fuel) due to being overloaded.
Mark the hex screw head so you can return it to the previous correct position--I did this for a few clients to convince and so prove to them that there was nothing left in their engine except the ability to make black smoke, especially if I upped the rack setting too. Both duly reset to previous set positions.

Thanks to OM the Scan below shows the red arrowed High Idle screw and the cover which it is under.
There is a double hex hole in the Idle Screw rear top cover for holding the adjuster screws in their adjusted place.


Cheers,
Eddie B.

Here are the correct governor diagrams for the 66D1651. Engines 66D1-5730 do not have a torque spring, just the stop.

Hi OM,
thank you again, it sure makes it easier when a person has the correct books--LOL

Eddie B.

"edb" wrote:

Hi waltini,
if your calculated hull speed is 8.5 knots and 8.5 knots is what you are currently traveling at with 1500 engine RPM then to me it would appear that all is as was originally designed as the prop etc. seems to be matched for these figures.
1500 RPM should make the unit economical.

An actual measurement of the current rack setting and a check in a current Rack Setting Book for your engine would tell us what HP the engine is capable of at the current 1500 RPM.

It could be that the engine is capable of more HP than your vessel requires to travel at 8.5 knots which tells us that the entire drive train has been set up correctly in the first instance--I stand to be corrected.

If the vessel and engine have lasted all this time without undue stress whilst traveling at its designed speed then I would leave well alone--as I said earlier our model trials at the Cat School showed there is nothing to be gained adding more HP to a vessel already traveling at its optimum hull speed except increased fuel consumption and decreased engine and drive train life.

Prop design is a smoke and mirrors scientific field all of its own we were told, and so we did little except to use 12 volt electric motor powered model boats with varying hull shapes and interchangeable pitched diameter and number of bladed props to see the effect of over pitching or under pitching the prop had on engine RPM and amperage draw(load) to tell us what the end net result was. This gave us a view into the murky world of prop design.
Somehow I have ended up with a prop slide rule calculator for props but have no idea how to use it.

The scan below shows the High Idle adjustment screw--if you wish to try and screw the screw out one half a turn to increase the engine RPM as an experiment and see what happens in regards to your hull speed and engine emitting black smoke (wasted fuel) due to being overloaded.
Mark the hex screw head so you can return it to the previous correct position--I did this for a few clients to convince and so prove to them that there was nothing left in their engine except the ability to make black smoke, especially if I upped the rack setting too. Both duly reset to previous set positions.

Scans below show the red arrowed High Idle screw and the cover which it is under.
There is a double hex hole in the rear cover for holding the adjuster screws in their adjusted place.
Be sure to align the semi-circular cutout on the Rack Collar with the aligning pin in said rear cover when you refit it.--There should also be a torque spring group in there that is not shown in the sectional views--be careful not to distort the blade spring with the small adjuster screw thread in said disc when handling things.

Cheers,
Eddie B.

thanks for the detailed explanation Ed, it seems as if the rumors i heard were true:cool2:

Gentleman I removed the stop solenoid tang from the governor housing and the max rpm increased to 1650 (from 1500) so obviously the frozen stop solenoid was impeding the fuel rack. As the cable controlling the fuel rack has two cables, one from the fly bridge and one from the main cabin. The two cables join in a reasonably complex junction box with one cable then going onto the engine.

Next step is to go for another trial and remove the control cable and move the throttle on the engine by hand. Because the governor has an oil pressure sensor I need to do the trial under way. I was mucking around with it by myself but racing around at full throttle with no one on the helm and me in the engine room I decided it wise to wait for a friend to come along. I know there is a way to bypass the governor oil pressure sensor but the bolt is all painted over and I hesitate to touch it lest I open another can of worms.

Anyway at 1650 it sounded good and no smoke and was faster than I really want to go so it's not the end of the world. Still it would be nice to sort it out!

Hi Waltini,
sounds like you are making headway--so to speak-- I guess the previous captain used to cruise at 1500 RPM and so the shut-off mechanism froze there.
Two station control cables paired to one master to the the bridge could be tricky to get equal RPM out of.
As a 5th year Dealer Apprentice I worked a floating suction cutter dredge, as per Von Schmidt design, back in 1966-7, that had 4 X D343 engines, paired side by side in a V form, each pair were in line and thru drive shafts linked to 2 gearboxes to drive the 28" suction pump by centrifugal clutches, one on each engine, so any one engine could be down for service as this was a 24 hour operation dredging channels and swing basins for the Barry Beach Bass Straight oil field complex then being built.
The system of cables utilised was hit and miss and no two engines ended up with same RPM settings at any speed setting even after exacting adjustments.

Cheers,
Eddie B.