Old Westerbeke Diesel overheat

[sailortonowhere]

I recently repowered (from 22 hp to 37 hp) to a old rebuilt Westerbeke Diesel (4-107 block). The engine runs great until you get above 1500 RPM. Then begins to overheat (fresh water cooled w/ heat exchanger). 1) I did not change prop, however since I powered UP this (ive been told) should not be a problem. 2) Everything else seems fine. I have tried different coolant ratios, different radiator caps, 3/4" hose for all raw water cooling. Heat exchanger works very good - I've tapped off my anti-siphon into the cockpit so that I can feel the temperature of the raw water - its gets very hot when the engine gets above 1500. Tried swapping the raw water and oil heat exchangers so that the engine gets the cooler water 1st - to no avail. 3) Because of space, my exhaust system consists of lead pipe forming a big upside-down "U" reaching above the waterline. Thus I have no muffler, but there is an anti-siphon loop from the output of the heat exhangers so no water can be forced or pulled into the engine. The exhaust system consists of 2" pipe with bends consisting of 4 - 90 degree elbows.<br /><br />Suggestions so far include:<br />a) too much back pressure. I've measured this and there is indeed a lot of back pressure from the exhaust. Would increasing the diameter of the pipe help? Otherwise, I'd have to go with a custom design to soften the elbows - would an automobile exhaust system (midas et. al) suffice?<br />b) internal cativation from the fresh water pump.<br />c) air bubbles in the fresh water system. I'm pretty sure there are no trapped bubbles, but dont know how to verify this.<br />d) water in fresh water system may be going to fast through heat exchange - possibly need to constrain the flow?<br />e) add in another raw water heat exchange - this to me would be masking the real problem.<br /><br />Before I try these suggestions, I'd like to get anybody's feed back on each. Also any other suggestions would be greatly appreciated.<br /><br />Thanks in advance.

 

[crazyray78]

Re: Old Westerbeke Diesel overheat

back pressure can cause this

 

[rolmops]

Re: Old Westerbeke Diesel overheat

When you say,your raw water gets very hot,could that mean that for whatever reason there is not enough volume of raw water passing through your system? With a larger powerplant you produce more heat.Maybe a good cleanout of the raw water unit could help.You will have to somehow increase raw waterflow so you can get rid of the excess heat.<br />good luck

 

[flashback]

Re: Old Westerbeke Diesel overheat

have you checked your thermostat? if it is hanging up it could cause your problem. shoot, for 5 bucks, go ahead and replace it........