Perkins diesel 135hp - running RPM and Temp

[Ryan Jepsen]

I have a 1979 39' SeaQuest Trawler with the original 135hp Perkins diesel with ~3800 hours, that is new to me. We just did our maiden voyage and things went generally well. The previous owner mentioned to run her at 1200-1400 rpm - which we did. We also pushed her to 1500 rpms for a bit and the water temp gauge went from steady at 180-195, to 230, the top end of the gauge. My question is this typical for these engines to not want to run at that high of an RPM or is this indicative of something else possibly more serious. Wondering what course of action I should take.

Thanks for the help,

Greenhorn,

ryan

 

[Nomad Willy]

Ryan,
Clean your heat exchanger tubes and perhaps install a new thermostat.

1500rpm propped to rated rpm at WOT .. is fine provided all else is.
It’s typical to run 300 or so rpm below rated rpm. Look it up for your engine. Continuous running max rpm is usually specified for marine engines.

 

[Dwk]

I would check coolant level,freshwater pump,raw water inpeller along with Willys suggestion to inspect heat exchanger for restriction. Our Perkins runs @ 1600-2000 rpm without a temperature increase.Good luck

 

[High Wire]

No that’s abnormally high. Should be 180-195F depending where you measure.
Make sure the coolant tank is full and you have good flow out of the exhaust. My exhaust riser was on its last leg so we replaced everything. We run 185F WOT now.

 

[C lectric]

THis engine should not run at anywhere near even 200oF at full tilt.

Change the impeller as a first step.

But there are other things that can cause this. I have posted my tome below. Read it through and if you have questions ask.

It sounds to me like you have a low water flow or a scaled up seawater side of the heat exchanger.
One question to answer though is when you backed off the rpm did the engine take a LONG time to drop the temperature or did it show signs of cooling quickly once the power level was reduced. Like 10 minutes vs 1/2 hr.

 

[jgwinks]

Look at the serial number on the injector pump, the last four numbers are the max RPM. My Perkins 6.354MGT's are 2750. Engine should be able to run 80% of that speed all day long without issue. So something's amiss, low coolant, flow restriction, bad impeller, etc.

 

[Jeff F]

Check the intake strainer first, if you have one. Also coolant level. Then impeller and flow end to end. This shouldn't be happening at any RPM.

Were you at full throttle at 1500? That's a different discussion . C'mon back when you've sorted the cooling.

 

[sunchaser]

I have a 1979 39' SeaQuest Trawler with the original 135hp Perkins diesel with ~3800 hours, that is new to me. We just did our maiden voyage and things went generally well. The previous owner mentioned to run her at 1200-1400 rpm - which we did. We also pushed her to 1500 rpms for a bit and the water temp gauge went from steady at 180-195, to 230, the top end of the gauge. My question is this typical for these engines to not want to run at that high of an RPM or is this indicative of something else possibly more serious. Wondering what course of action I should take.

Thanks for the help,

Greenhorn,

ryan

Did you conduct a full throttle test during the sea Trial? If so, what maximum RPM was achieved and temperatures at that point?

 

[mcarthur]

If yours is the M135 Perkins-Sabre, it's the same as our two. While rated to 2600rpm, ours are limited to 2400 and we easily run at 2000 without any change in temp. They sound best at about 1600-1700rpm though.

 

[sunchaser]

If yours is the M135 Perkins-Sabre, it's the same as our two. While rated to 2600rpm, ours are limited to 2400 and we easily run at 2000 without any change in temp. They sound best at about 1600-1700rpm though.

You are correct on RPMs for the Perkins Sabre. Likely older Perkins model though as the PS weren't introduced until about 22 years after the OP's boat was built.

 

[mcarthur]

You are correct on RPMs for the Perkins Sabre. Likely older Perkins model though as the PS weren't introduced until about 22 years after the OP's boat was built.

Whoops - doh! I should have noticed the OP dates...

 

[kapnd]

The old Perkins have seawater cooled cast iron exhaust manifolds and elbows that are prone to corrosion issues. The coolant loop can be modified to include the exhaust manifold, and the elbow replaced with a stainless steel item.
Be aware that this modification will not support high speed running!
Best to start by going through the entire raw water system, from intake grating to exhaust exit to assess its condition and probably figure out where the overheat problem is coming from.

 

[sunchaser]

As well as a complete cooling system go through, assessing sea trial findings and overpropping , if any, is a good idea as suggested in post #8.