I have a 1985 C36 with a M25 engine
I’m unable to get more that 2200 RPM from my M25 engine. Following verification of RPM with a hand help tach and checks of various engine components It was discovered that the previous owner had installed fuel inject pump rated for maximum of 2200 RPM not sure why.
I’m going to replace the inject pump with the proper pump and have the following question:
As the fuel injector pump controls the engine RPM and the pump offered by Torreseen Marine (Part #300191) is the same pump supplied for both the M25 & M25XP. The max RPM of each engine is different. Is there pump installation differences for each engine, example placement of shims between pump and engine mount?
Keith Hull #431
SV: Victoria Dos
Keith & Donna
SV: Victoria Dos
Hull #431
Sea of Cortez, Mexico
Keith,
Have you tried to adjust the maximum RPM. If not there is an adjustment for that. On the forward side of the engine just above and slightly outboard of the water pump there is a cap nut. If you remove the cap nut you will find a set screw and jamb nut. Loosen the jamb nut and turn the screw counter clockwise to increase RPM or clockwise to decrease RPM. This is the adjustment stop for the fuel rack in the fuel pump and is controlled by the governor. You can see a picture of it in the article I did on the overhaul of my 25XP on this site. Go to Articles, Maintenance and look for 25XP overhaul, the last picture show it fairly clearly, I painted mine red.
When the throttle is set for any intermediate power the govenor controls RPM by controlling this racks movement for and aft to increase or decrease fuel flow. Max rpm is controlled by limiting the forward movement of the rack with this set screw.
Use caution when making your adjustment as you may exceed max RPM if this screw is adjusted out to far. You can also adjust this underway but, under a load you may note the RPM may not increase beyond a certain point and your exhaust will start getting very black. If this happens to far below max RPM you may be overproped, or your bottom is very dirty.
The shims you mention are to adjust injection timing, they are also required if you have the block milled as this lowers the pump in the block slightly and effects injector timing.
You mention that the fuel injector is for a lower RPM installation, I am unfamilure with this, you may want to talk to an injector shop about this issue as well.
Cepheus dream
C36 MK I # 825
MK I Tech Editor No Mas
Thanks Steve:
I have not tried adjusting the RPM setting. I will give this a try. I reviewed the picture of your engine rebuild. Great article and pictures.
Another question I have after viewing your engine pictures. The heater hose from the water pump to your water heater appears to be 1/2 or 5/8 inch hose. The water pump outlets (bypass) from my water pump for the heater supply is 3/8 inch. Is your water pump connections 3/8 inch and if so how did you transition from 3/8 to lager heater hose?
Keith (Hull 431)
SV: Victoria Dos
Keith & Donna
SV: Victoria Dos
Hull #431
Sea of Cortez, Mexico
Keith,
I had to go back to the pictures to refresh my memory regarding the hoses. I did not change the ID of the hose, the fact that one of these hoses failed causing my engines demise, I was sensitive about these hoses. When I replaced them I used some aircraft low pressure MIL 6000 series hose (1000 psi burst pressure). This hose is two ply with a heavy outer wall for chafe protection as chafe was the culprit on the old hose failing. If chafe is a problem on this hose, it should become evident long before it chafes to the inner core.
As a procrastinator I must confess, I have not replaced the hoses from the water heater to the engine compartment. Though I did install a temp warning system on my engine.
I hope you can adjust up your engine RPM, let us know the out come.
Cepheus dream
C36 MK I # 825
MK I Tech Editor No Mas