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Hunter 28.5 powered by Yanmar 2GM20F

Nov 6, 2019
9
Hunter 28.5 Lake ray Hubbard
Hi this topic it is about the engine Yanmar 2GM20F , I’m going to show you the modifications and maintenance preform by my self.
The first corrective maintenance I did to my engine was the change of the mixing or exhaust elbow. I had to change the engine elbow Because It Was Broken, the joint and the elbow was in bad shape, the joint was leaking fumes and the elbow was crack. It was a pretty
Easy change..... if you have all the engine compartment wall removed which I have. Feel free to correct, ask and comment thanks!
 

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Jun 1, 2016
103
Hunter 28.5 Lake City, MN
I have a Hunter 28.5 also, and back in 2017, I had a slow anti-freeze leak that I had to contend with. Getting the back off the engine compartment was the most difficult part, as I recall. It was more than removing screws, but had to cut some of the board off at the bottom, so that it would slide out...

While I was in there, I checked my exhaust elbow and several other things. For the leak, I cleaned the cooling system and replaced all the gaskets, still leaked. Put in some “Barr’s Stop Leak” and that fixed it!

The engine work is SO much easier with the back remove...

MIke
 
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Nov 6, 2006
8,477
Hunter 34 Mandeville Louisiana
Not familiar with the details of that installation, ut it seems that there should be a vented loop in the sea water hose from the exchanger to the elbow?
 
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Likes: No Tangas
Nov 6, 2019
9
Hunter 28.5 Lake ray Hubbard
I have a Hunter 28.5 also, and back in 2017, I had a slow anti-freeze leak that I had to contend with. Getting the back off the engine compartment was the most difficult part, as I recall. It was more than removing screws, but had to cut some of the board off at the bottom, so that it would slide out...

While I was in there, I checked my exhaust elbow and several other things. For the leak, I cleaned the cooling system and replaced all the gaskets, still leaked. Put in some “Barr’s Stop Leak” and that fixed it!

The engine work is SO much easier with the back remove...

MIke
Yes mike it is a really easy engine to work , comprare to others engine it have just a few screw, have a nice day
 

Attachments

Nov 6, 2019
9
Hunter 28.5 Lake ray Hubbard
Not familiar with the details of that installation, ut it seems that there should be a vented loop in the sea water hose from the exchanger to the elbow?
Hi! Kloudie1 yes, I removed the vented loop, I decide for testing purpose to connect the mixing chamber directly to the elbow and it works great ! No overheating or nothing after a 2 hr cruise around the lake looking for failures or overheating
 

Attachments

Jan 4, 2006
2,561
Hunter H-310 West Vancouver, B.C.
it seems that there should be a vented loop in the sea water hose from the exchanger to the elbow?
You are so right ......................... HOWEVER, I had the vacuum breaker start to leak at the vent a few years back and what a #%$^%&* mess that was :banghead:. Spent a week cleaning and repainting where the sea water had attacked the block. There is no place to lead a vacuum breaker vent to a safe place as the engine is housed in a Nike shoe box.

Engine Housing.jpg


Seeing as how mounting a safe vent tube was out of the question, I took a few measurements of the sea water lever around the engine using a clear vinyl tube connected to the cooling sea water thru hull, and measured the sea water level as 4" below the bottom of the mixing elbow. Lookin' better :confused:. Next, I was curious as to how much resistance the static raw water pump presented to water flow. Again, out comes the clear vinyl tubing and I attached it to the raw water inlet to the cooling system with the valve closed.

100_1933.JPG


Added enough water to the tube until the water lever was 2" above the bottom of the mixing elbow (6" above sea level). The water flow was almost non-existent due to the resistance of the raw water pump. It took an 8" head of water above the bottom of the mixing elbow (12" above static sea level) to get any kind of flow into the engine and out into the exhaust.

I learned to live without a vacuum breaker, and with the extremely remote risk of flooding the exhaust :p.

PS. when the boat is under sail at about 5 kn. and the engine off, the dynamic sea water pressure at the thru hull drops 3" below the static sea water pressure. Bernoulli or somebody like that:stir:.

It works but I'm not going to crow about it as that's just looking for trouble :yikes:.
 
Nov 6, 2019
9
Hunter 28.5 Lake ray Hubbard
You are so right ......................... HOWEVER, I had the vacuum breaker start to leak at the vent a few years back and what a #%$^%&* mess that was :banghead:. Spent a week cleaning and repainting where the sea water had attacked the block. There is no place to lead a vacuum breaker vent to a safe place as the engine is housed in a Nike shoe box.

View attachment 171756

Seeing as how mounting a safe vent tube was out of the question, I took a few measurements of the sea water lever around the engine using a clear vinyl tube connected to the cooling sea water thru hull, and measured the sea water level as 4" below the bottom of the mixing elbow. Lookin' better :confused:. Next, I was curious as to how much resistance the static raw water pump presented to water flow. Again, out comes the clear vinyl tubing and I attached it to the raw water inlet to the cooling system with the valve closed.

View attachment 171757

Added enough water to the tube until the water lever was 2" above the bottom of the mixing elbow (6" above sea level). The water flow was almost non-existent due to the resistance of the raw water pump. It took an 8" head of water above the bottom of the mixing elbow (12" above static sea level) to get any kind of flow into the engine and out into the exhaust.

I learned to live without a vacuum breaker, and with the extremely remote risk of flooding the exhaust :p.

PS. when the boat is under sail at about 5 kn. and the engine off, the dynamic sea water pressure at the thru hull drops 3" below the static sea water pressure. Bernoulli or somebody like that:stir:.

It works but I'm not going to crow about it as that's just looking for trouble :yikes:.
NICE and clean boat !!
 
Apr 8, 2010
1,178
Ericson Yachts Olson 34 Portland OR
You are so right ......................... HOWEVER, I had the vacuum breaker start to leak at the vent a few years back and what a #%$^%&* mess that was :banghead:. Spent a week cleaning and repainting where the sea water had attacked the block. There is no place to lead a vacuum breaker vent to a safe place as the engine is housed in a Nike shoe box.

View attachment 171756

Seeing as how mounting a safe vent tube was out of the question, I took a few measurements of the sea water lever around the engine using a clear vinyl tube connected to the cooling sea water thru hull, and measured the sea water level as 4" below the bottom of the mixing elbow. Lookin' better :confused:. Next, I was curious as to how much resistance the static raw water pump presented to water flow. Again, out comes the clear vinyl tubing and I attached it to the raw water inlet to the cooling system with the valve closed.

View attachment 171757

Added enough water to the tube until the water lever was 2" above the bottom of the mixing elbow (6" above sea level). The water flow was almost non-existent due to the resistance of the raw water pump. It took an 8" head of water above the bottom of the mixing elbow (12" above static sea level) to get any kind of flow into the engine and out into the exhaust.

I learned to live without a vacuum breaker, and with the extremely remote risk of flooding the exhaust :p.

PS. when the boat is under sail at about 5 kn. and the engine off, the dynamic sea water pressure at the thru hull drops 3" below the static sea water pressure. Bernoulli or somebody like that:stir:.

It works but I'm not going to crow about it as that's just looking for trouble :yikes:.
It might just be the angle of view, but the stuffing box hose sure looks like it sags down a bit. I once had that happen on a boat when, over the years, the rubber in the mounts degraded and collapsed somewhat. I caught the problem just as the shaft was an eighth inch from rubbing on the bottom of the shaft tube. With the engine remounted and aligned with new mounts installed, and the shaft centered in the tube, potential problem solved.
 
Jan 4, 2006
2,561
Hunter H-310 West Vancouver, B.C.
It might just be the angle of view, but the stuffing box hose sure looks like it sags down a bit.
I see what you mean about the photo, but no, haven't seen any any drop in the level of the engine in the alignment of the engine when doing an alignment every 2-3 years.

So far lucky as the mounts are the original from 1999. Except for the rear starboard which managed to get soaked with diesel fuel many years ago. Replaced that one only as a precaution against rubber deterioration. Almost have the loan paid off for the purchase of that one.
 
Last edited:
Jul 29, 2018
40
O'Day 35 Interlude Buzzards Bay
If they're 20 years old, there's more than a good chance your mounts are sitting lower - if you get a chance, slide your packing gland and stern hose tube forward and see how the shaft is sitting in the tube - you can use a drill bit of the right diameter to ensure it is centered. I was surprised how low my shaft was sitting when I did this and the mounts weren't nearly 20 years old. From the outside the shaft looked like it was centered. The shaft hitting the stern tube can cause expensive damage.
 
Jan 4, 2006
2,561
Hunter H-310 West Vancouver, B.C.
If they're 20 years old, there's more than a good chance your mounts are sitting lower
It also depends on the construction of the mount itself. Here's a picture of the old mount that was removed showing the construction of the rubber shock absorbing material:

Engine Mount.JPG


After seeing the condition of this mount, I really started inspecting these hidden little gems on an annual basis.

As mentioned before, this item was not cheap ten years ago:

Mount.jpg


When comparing mounts, something like this may not hold up as long:

Perkins.JPG
 
Jul 29, 2018
40
O'Day 35 Interlude Buzzards Bay
True, I must admit mine are like the second ones. I know those Universal mounts are good but at more than 5 times the price, I will be replacing mine with the same model. However, my Catalina 30 had the original Universal mounts - at 18 years, the shaft was almost touching the bottom of the stern tube, I would still make sure.
 
Jan 4, 2006
2,561
Hunter H-310 West Vancouver, B.C.
at 18 years, the shaft was almost touching the bottom of the stern tube, I would still make sure.
Thanks for the cautionary note and you've upset me enough that I will do a double check, during the alignment check this winter, just to ensure the shaft is remaining centred in stern tube.

However, having said that, other that the first alignment done in 2001, I have not had to adjust the height of the engine during an alignment check. During that first alignment, the height of the engine was waaaaay above the height of the prop shaft and required the engine to be lowered considerably. Ever since, been good. Also, I keep the mounts in pristine condition and avoid any fuel or oil contamination under penalty of having to replace it.

With the price of my mounts being five times the cost of yours, I would think you can afford to replace yours five time as often. And of course, as you know, replacing engine mounts is just a simple case of slip out the old and slip in the new, all the while, banging your head against the engine to see if maybe that will help dislodge the old mount:banghead:.