Update to this strung out thread. Lots of layers to cover here.
First off, I need to give a proper callout to everyone who’s responded, and pay, once again, my homage to T2stroke, Fleetwin, FrankR, Pappy, Mumbles, and several others who are willing to share secrets with the rest of us who just haven’t put in the hours they have. Everything after this sentence simply corroborates their previous posts.
For the recent respondents — once I have this motor (which currently is on my personal vessel, which mean I’ve spent extra time on it with the cosmetics…but the same stuff I do with all motors mechanically) back together, I will post pictures of it.
So T2stroke – I have torn apart my first 4 of these motors in the last month, and this is (ironically being my personal motor), the 1st one that has clearly had the situation you have been warning me about since last January during our first phone call ever.
Fleetwin – this is what you have been mentioning in most of your posts when asking if the motor(s) were salt water or overheated. Well this motor seems to be a mixed use motor, at least 30% of the fasteners have snapped when I’ve pulled this thing apart, and at this point I’ve pulled the thermostat cover and cylinder head (3 broken bolts needing boring out and retapping) and now the exhaust bypass (3 broken bolts, 2 retaped, 1 left with the stud there…). If this thing doesn’t pump like a champ by tomorrow afternoon, then there’s only 1 thing left…the upper water tube grommet…and for the love of the almighty I hope it doesn’t come to that.
Here is a picture of my 1978 inner exhaust baffle (right) next to a 1981 baffle (from a donor motor). PLEASE NOTE that this picture seems to make both seem different sizes (wrong angle), they are identical in dimensions.
Pretty significant changes in just a couple of years, and to T2stroke’s point, I can see why my motor had poor water pumping. In fact I’m more impressed that the new impeller I installed had enough power to overcome the intrusion of exhaust gasses. My motor had erratic water pumping. I ran it for 6 hours with no thermostat and it was actually running cold, but the telltale never showed powerful waterflow. And that is the reason why I tore it apart and here are the differences:
#1 (right baffle) shows the original water holes meant to distribute water onto the exhaust baffle to keep it at an acceptable temperature, and help water flow into the cylinder jacket.
#1 (left baffle 1980+) shows the enlargement of water flow to the cylinder jacket after initially passing the exhaust baffle. That is at least 10x larger.
#2 shows how these ‘deflectors’ were designed to redirect exhaust down into the exhaust housing at the powerhead, but mechanically, I surmise this also provides a significant structural component, as a fold in metal has huge benefits
#3 allows water to cover more of the baffle (really where the original design separates from the inner/possibly outer gaskets, allowing exhaust pressure to suppress water supply to the powerhead) to keep it cool and from deforming even if, say waterflow is restricted with a weak water pump, plastic bag over the intake, whatever
#4 (bottom) is to allow water to flow into the high risk area immediately from the copper water tube.
#4 (top) are large areas to allow cold water to first meet this exhaust area and I would surmise, stop the warping of the baffle.
From all these improvements, all I can conclude is that everything was made to stop a common issue, and to keep the motor from overheating even during poor water flow. But let’s say your thermostat gets stuck shut, or somehow dirt/debris clogs up the holes either on the exhaust baffle leading to the cylinder jacket, or the cylinder head itself. You still have water flowing through the baffle reducing the risk of a warp. Still have an overheat situation, but hopefully the lesser of two evils.
Just like the 9.9/15 designs…the telltale may show plenty of water pumping, but not necessarily a correctly functioning cooling passageway/system. These 25/35hp motors are very similar in design to there little bro 9.9/15hp siblings.
My motor doesn’t have the provision for the overheat alarm on the control box, but I plan to update it with a newer cylinder head to take advantage of this valuable feature.
Seems as if all these improvements came through in 1980 (as mentioned by everyone), but as the saying goes, a picture is worth a thousand words.
Here are a couple of pics of the warped baffle. First one I’ve seen personally, tried to get some good angles to show the warping. I guess when you design a product to be mass produced, you don’t know these types of things are going to happen until the ‘rubber hits the road.’ But in the repair business, the books don’t tell you about this stuff until you see it first hand.
I have to say that I didn’t even notice the warping when I first pulled the baffle off until I took a 2nd look at it. It was painfully obvious that this is probably the root of my cooling system issues, but I can only imagine if the baffle is less warped how it might be difficult to recognize this same issue?
In terms of mounting – I figured out (after my 1 day initial run of the self-constructed tritoon last Sunday), that my original transom design was correct, placing the ventilation plate in line with the bottom of the middle tube. HOWEVER, the panther power trim has about a 3" rise, which lifts the motor the equivalent difference, and is way too high for any small motor on an aluminum boat/vessel, and caused ventilation at anything above 1/3rd throttle for me. So hopefully by this Wednesday both the motor and vessel will be revised. I hit 14MPH at 1/3rd throttle on my mini-tritoon, so I’m thinking 30MPH may not be out of the question once everything is fixed 😆 😀 😮 😯 😮
Prop is a standard 10 x 13.